How many electron pairs does carbon share in order to complete its valence shell?

A) 1
B) 2
C) 3

D) 4
E) 8

D

A carbon atom is most likely to form which of the following bonds with other atoms?

A) ionic bond
B) hydrogen bond
C) covalent bond

D) covalent bonds and hydrogen bonds
E) ionic bonds, covalent bonds, and hydrogen bonds

C

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers, that is, molecules that
A) have identical chemical formulas but differ in the branching of their carbon skeletons.
B) are mirror images of one another.

C) exist in either linear chain or ring forms.
D) differ in the location of their double bonds.
E) differ in the arrangement of atoms around their double bonds.

B

What determines whether a carbon atom's covalent bonds to other atoms are in a tetrahedral configuration or a planar configuration?
A) the presence or absence of bonds with oxygen atoms
B) the presence or absence of double bonds between the carbon atom and other atoms

C) the polarity of the covalent bonds between carbon and other atoms

D) the presence or absence of bonds with nitrogen atoms
E) the solvent that the organic molecule is dissolved in

B

A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?
A) It lacks an asymmetric carbon, and it is probably a fat or lipid.
B) It should dissolve in water.

C) It should dissolve in a nonpolar solvent.

D) It won't form hydrogen bonds with water.

E) It is hydrophobic.

B

Which two functional groups are always found in amino acids?

A) ketone and methyl
B) carbonyl and amino
C) carboxyl and amino

D) amino and sulfhydryl
E) hydroxyl and carboxyl

C

Amino acids are acids because they always possess which functional group?

A) amino
B) carbonyl
C) carboxyl

D) phosphate
E) hydroxyl

C

A carbon skeleton is covalently bonded to both an amino group and a carboxyl group. When placed in water it
A) would function only as an acid because of the carboxyl group.
B) would function only as a base because of the amino group.

C) would function as neither an acid nor a base.
D) would function as both an acid and a base.
E) is impossible to determine how it would function

D

Which chemical group can act as an acid?

A) amino
B) carbonyl
C) carboxyl

D) hydroxyl
E) methyl

C

Molecules with which functional groups may form polymers via dehydration reactions?

A) hydroxyl groups
B) carbonyl groups
C) carboxyl groups

D) either carbonyl or carboxyl groups

E) either hydroxyl or carboxyl groups

E

Which of the following is not a monomer/polymer pairing?

A) monosaccharide/polysaccharide
B) amino acid/protein
C) triglyceride/phospholipid bilayer

D) deoxyribonucleotide/DNA

E) ribonucleotide/RNA

C

Which of these molecules is not formed by dehydration reactions?

A) fatty acids
B) disaccharides
C) DNA

D) protein
E) amylose

A

Which of the following is not a polymer?

A) glucose
B) starch
C) cellulose

D) chitin
E) DNA

A

What is the chemical reaction mechanism by which cells make polymers from monomers?

A) phosphodiester linkages
B) hydrolysis
C) dehydration reactions

D) ionic bonding of monomers
E) the formation of disulfide bridges between monomers

C

How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?
A) 12
B) 11

C) 10
D) 9
E) 8

C

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
A) Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers. B) Dehydration reactions eliminate water from lipid membranes, and hydrolysis makes lipid membranes water permeable.

C) Dehydration reactions can occur only after hydrolysis.
D) Hydrolysis creates monomers, and dehydration reactions break down polymers.
E) Dehydration reactions ionize water molecules and add hydroxyl groups to polymers; hydrolysis reactions release hydroxyl groups from polymers.

A

Which of the following is an example of hydrolysis?
A) the reaction of two monosaccharides, forming a disaccharide with the release of water
B) the synthesis of two amino acids, forming a peptide with the release of water
C) the reaction of a fat, forming glycerol and fatty acids with the release of water
D) the reaction of a fat, forming glycerol and fatty acids with the consumption of water
E) the synthesis of a nucleotide from a phosphate, a pentose sugar, and a nitrogenous base with the production of a molecule of water

D

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?
A) C18H36O18
B) C18H32O16

C) C6H10O5

D) C18H10O15
E) C3H6O3

B

Which of the following is true of both starch and cellulose?

A) They are both polymers of glucose.
B) They are cis-trans isomers of each other.
C) They can both be digested by humans.

D) They are both used for energy storage in plants.
E) They are both structural components of the plant cell wall.

A

The bonding of two amino acid molecules to form a larger molecule requires

A) the release of a water molecule.
B) the release of a carbon dioxide molecule.
C) the addition of a nitrogen atom.

D) the addition of a water molecule.
E) the release of a nitrous oxide molecule.

A

Humans can digest starch but not cellulose because
A) the monomer of starch is glucose, whereas the monomer of cellulose is galactose.
B) humans have enzymes that can hydrolyze the β glycosidic linkages of starch but not the α glycosidic linkages of cellulose.
C) humans have enzymes that can hydrolyze the α glycosidic linkages of starch but not the β glycosidic linkages of cellulose.
D) humans harbor starch-digesting bacteria in the digestive tract.
E) the monomer of starch is glucose, whereas the monomer of cellulose is glucose with a nitrogen-containing group.

C

Polysaccharides, triacylglycerides, and proteins are similar in that they

A) are synthesized from monomers by the process of hydrolysis.
B) are synthesized from subunits by dehydration reactions.
C) are synthesized as a result of peptide bond formation between monomers.

D) are decomposed into their subunits by dehydration reactions.

E) all contain nitrogen in their monomer building blocks.

B

Dehydration reactions are used in forming which of the following compounds?

A) triacylglycerides
B) polysaccharides
C) proteins

D) triacylglycerides and proteins only
E) triacylglycerides, polysaccharides, and proteins

E

DNAase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNAase?

A) The two strands of the double helix would separate.
B) The phosphodiester bonds between deoxyribose sugars would be broken.

C) The purines would be separated from the deoxyribose sugars.
D) The pyrimidines would be separated from the deoxyribose sugars.

E) All bases would be separated from the deoxyribose sugars.

B

Which of the following is true of cellulose?
A) It is a polymer composed of enantiomers of glucose.
B) It is a storage polysaccharide for energy in plant cells.
C) It is digestible by bacteria in the human gut.
D) It is a major structural component of plant cell walls.
E) It is a polymer composed of enantiomers of glucose, it is a storage polysaccharide for energy in plant cells, it is digestible by bacteria in the human gut, and it is a major structural component of plant cell walls.

D

Which of the following polymers contain nitrogen?

A) starch
B) glycogen
C) cellulose

D) chitin
E) amylopectin

D

Which of the following classes of biological molecules consist of both small molecules and macromolecular polymers?
A) lipids
B) carbohydrates

C) proteins
D) nucleic acids
E) Lipids, carbohydrates, proteins, and nucleic acids all consist of only macromolecular polymers.

B

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down?
A) starch
B) cellulose

C) chitin
D) starch and chitin only
E) starch, cellulose, and chitin

A

On food packages, to what does the term insoluble fiber refer?

A) cellulose
B) polypeptides
C) starch

D) amylopectin
E) chitin

A

A molecule with the chemical formula C6H12O6 is probably a

A) carbohydrate.

B) lipid.
C) monosaccharide
D) carbohydrate and lipid only.
E) carbohydrate and monosaccharide only.

E

Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
A) as a pentose
B) as a hexose

C) as a monosaccharide

D) as a disaccharide
E) as a polysaccharide

D

All of the following are polysaccharides except A) lactose.
B) glycogen.
C) chitin.

D) cellulose.
E) amylopectin.

A

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other?
A) Testosterone and estradiol are structural isomers but have the same molecular formula. B) Testosterone and estradiol are cis-trans isomers but have the same molecular formula. C) Testosterone and estradiol have different functional groups attached to the same carbon skeleton.

D) Testosterone and estradiol have distinctly different chemical structures, with one including four fused rings of carbon atoms, whereas the other has three rings.
E) Testosterone and estradiol are enantiomers of the same organic molecule.

C

Why are hydrocarbons insoluble in water?
A) The majority of their bonds are polar covalent carbon-to-hydrogen linkages.
B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

C) They are hydrophilic.
D) They exhibit considerable molecular complexity and diversity.
E) They are lighter than water.

B

Which of the following statements concerning saturated fats is not true?

A) They are more common in animals than in plants.
B) They have multiple double bonds in the carbon chains of their fatty acids.

C) They generally solidify at room temperature.

D) They contain more hydrogen than unsaturated fats having the same number of carbon atoms.

E) They are one of several factors that contribute to atherosclerosis.

B

A molecule with the formula C18H36O2 is probably a

A) carbohydrate.

B) fatty acid.
C) protein.
D) nucleic acid.
E) hydrocarbon.

B

Which of the following statements is true for the class of biological molecules known as lipids?
A) They are insoluble in water.
B) They are made from glycerol, fatty acids, and phosphate.

C) They contain less energy than proteins and carbohydrates.

D) They are made by dehydration reactions.
E) They contain nitrogen.

A

The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. What is the result of adding hydrogens to vegetable oil?
A) The hydrogenated vegetable oil has a lower melting point.
B) The hydrogenated vegetable oil stays solid at room temperature.

C) The hydrogenated vegetable oil has more "kinks" in the fatty acid chains.

D) The hydrogenated vegetable oil has fewer trans fatty acids.
E) The hydrogenated vegetable oil is less likely to clog arteries.

B

Which of the following is true regarding saturated fatty acids?
A) They are the predominant fatty acid in corn oil.
B) They have double bonds between the carbon atoms of the fatty acids.

C) They are the principal molecules in lard and butter.
D) They are usually liquid at room temperature.
E) They are usually produced by plants.

C

Large organic molecules are usually assembled by polymerization of a few kinds of simple subunits. Which of the following is an exception to this statement?
A) a steroid
B) cellulose

C) DNA
D) an enzyme
E) a contractile protein

A

Why are human sex hormones considered to be lipids?

A) They are essential components of cell membranes.
B) They are not soluble in water.
C) They are made of fatty acids.

D) They are hydrophilic compounds.

E) They contribute to atherosclerosis.

B

All of the following contain amino acids except A) hemoglobin.
B) cholesterol.
C) antibodies.

D) enzymes.
E) insulin.

B

There are 20 different amino acids. What makes one amino acid different from another? A) different side chains (R groups) attached to a carboxyl carbon
B) different side chains (R groups) attached to the amino groups
C) different side chains (R groups) attached to an α carbon

D) different structural and optical isomers

E) different asymmetric carbons

C

Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?
A) 101
B) 100

C) 99
D) 98
E) 97

C

Which bonds are created during the formation of the primary structure of a protein?

A) peptide bonds
B) hydrogen bonds
C) disulfide bonds

D) phosphodiester bonds
E) peptide bonds, hydrogen bonds, and disulfide bonds

A

What maintains the secondary structure of a protein?
A) peptide bonds
B) hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond
C) disulfide bonds
D) hydrophobic interactions
E) hydrogen bonds between the R groups

B

Which type of interaction stabilizes the α helix and the β pleated sheet structures of proteins? A) hydrophobic interactions
B) disulfide bonds
C) ionic bonds

D) hydrogen bonds
E) peptide bonds

D

Which level of protein structure do the α helix and the β pleated sheet represent?

A) primary
B) secondary
C) tertiary

D) quaternary
E) primary, secondary, tertiary, and quaternary

B

The amino acids of the protein keratin are arranged predominantly in an α helix. This secondary structure is stabilized by
A) covalent bonds.
B) peptide bonds.

C) ionic bonds.
D) polar bonds.
E) hydrogen bonds.

E

The tertiary structure of a protein is the
A) bonding together of several polypeptide chains by weak bonds.
B) order in which amino acids are joined in a polypeptide chain.
C) unique three-dimensional shape of the fully folded polypeptide.
D) organization of a polypeptide chain into an α helix or β pleated sheet.
E) overall protein structure resulting from the aggregation of two or more polypeptide subunits.

C

What type of covalent bond between amino acid side chains (R groups) functions in maintaining a polypeptide's specific three-dimensional shape?
A) ionic bond
B) hydrophobic interaction

C) van der Waals interaction

D) disulfide bond
E) hydrogen bond

D

At which level(s) of protein structure are interactions between the side chains (R groups) most important?
A) primary
B) secondary

C) tertiary
D) quaternary
E) primary, secondary, tertiary, and quaternary

C

The R group or side chain of the amino acid serine is -CH2-OH. The R group or side chain of the amino acid leucine is -CH2-CH-(CH3)2. Where would you expect to find these amino

acids in a globular protein in aqueous solution?
A) Serine would be in the interior, and leucine would be on the exterior of the globular protein. B) Leucine would be in the interior, and serine would be on the exterior of the globular protein. C) Both serine and leucine would be in the interior of the globular protein.
D) Both serine and leucine would be on the exterior of the globular protein.
E) Both serine and leucine would be in the interior and on the exterior of the globular protein.

B

Misfolding of polypeptides is a serious problem in cells. Which of the following diseases is (are) associated with an accumulation of misfolded polypeptides?
A) Alzheimer's only
B) Parkinson's only

C) diabetes mellitus only
D) Alzheimer's and Parkinson's only
E) Alzheimer's, Parkinson's, and diabetes mellitus

D

Changing a single amino acid in a protein consisting of 325 amino acids would

A) alter the primary structure of the protein but not its tertiary structure or function.

B) cause the tertiary structure of the protein to unfold.
C) always alter the biological activity or function of the protein.

D) always alter the primary structure of the protein and disrupt its biological activity.
E) always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and sometimes affect its biological activity.

E

Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits

A) altered primary structure.
B) altered secondary structure.
C) altered tertiary structure.
D) altered quaternary structure.
E) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered.

E

In a normal cellular protein, where would you expect to find a hydrophobic amino acid such as valine?
A) in the interior of the folded protein, away from water
B) on the exterior surface of the protein, interacting with water

C) in the transmembrane portion interacting with lipid fatty acid chains
D) in the interior of the folded protein, away from water, or in a transmembrane portion interacting with lipid fatty acid chains
E) anywhere in the protein, with equal probability

D

If cells are grown in a medium containing radioactive 35S, which of these molecules will be labeled?
A) phospholipids
B) nucleic acids

C) proteins
D) amylose
E) both proteins and nucleic acids

C

How will brief heating (to 95°C) affect macromolecular structures in aqueous solution?

A) DNA duplexes will unwind and separate.
B) Proteins will unfold (denature).
C) Starch will hydrolyze into monomeric sugars.

D) Proteins will hydrolyze into amino acids.
E) DNA duplexes will unwind and separate, and proteins will unfold (denature).

E

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct?
A) The 5' end has a hydroxyl group attached to the number 5 carbon of ribose.
B) The 5' end has a phosphate group attached to the number 5 carbon of ribose.

C) The 5' end has phosphate attached to the number 5 carbon of the nitrogenous base. D) The 5' end has a carboxyl group attached to the number 5 carbon of ribose.
E) The 5' end is the fifth position on one of the nitrogenous bases.

B

One of the primary functions of RNA molecules is to

A) transmit genetic information to offspring.
B) function in the synthesis of proteins.
C) make a copy of itself, thus ensuring genetic continuity.

D) act as a pattern or blueprint to form DNA.

E) form the genes of higher organisms.

B

If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?
A) phospholipids
B) DNA

C) RNA
D) both DNA and RNA
E) proteins

C

Which of the following descriptions best fits the class of molecules known as nucleotides?

A) a nitrogenous base and a phosphate group
B) a nitrogenous base and a pentose sugar
C) a nitrogenous base, a phosphate group, and a pentose sugar

D) a phosphate group and an adenine or uracil E) a pentose sugar and a purine or pyrimidine

C

Which of the following are nitrogenous bases of the pyrimidine type?

A) guanine and adenine
B) cytosine and uracil
C) thymine and guanine

D) ribose and deoxyribose

E) adenine and thymine

B

Which of the following are nitrogenous bases of the purine type?

A) cytosine and guanine
B) guanine and adenine
C) adenine and thymine

D) thymine and uracil
E) uracil and cytosine

B

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?
A) 10
B) 20

C) 40
D) 80
E) impossible to tell from the information given

C

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of
A) 120 adenine and 120 uracil molecules.
B) 120 thymine and 120 adenine molecules.

C) 120 cytosine and 120 thymine molecules. D) 120 adenine and 120 cytosine molecules. E) 120 guanine and 120 thymine molecules.

B

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA

A) is a six-carbon sugar and the sugar in RNA is a five-carbon sugar.
B) can form a double-stranded molecule.
C) is an aldehyde sugar and the sugar in the RNA is a keto sugar.

D) is in the α configuration and the sugar in RNA is in the β configuration.

E) contains one less oxygen atom.

E

Which of the following statements best summarizes the differences between DNA and RNA?

A) DNA encodes hereditary information, whereas RNA does not.
B) The bases in DNA form base-paired duplexes, whereas the bases in RNA do not.
C) DNA nucleotides contain a different sugar than RNA nucleotides.

D) DNA contains the base uracil, whereas RNA contains the base thymine.
E) DNA encodes hereditary information, whereas RNA does not; the bases in DNA form base- paired duplexes, whereas the bases in RNA do not; and DNA nucleotides contain a different sugar than RNA nucleotides.

C

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence
A) 5'TAACGT3'.
B) 5'TGCAAT3'.

C) 5'UAACGU3'.
D) 3'UAACGU5'.
E) 5'UGCAAU3'.

B

What is the structural feature that allows DNA to replicate?

A) sugar-phosphate backbone
B) complementary pairing of the nitrogenous bases
C) disulfide bonding (bridging) of the two helixes

D) twisting of the molecule to form an α helix

E) three-component structure of the nucleotides

B

If cells are grown in a medium containing radioactive 32P-labeled phosphate, which of these molecules will be labeled?
A) phospholipids
B) nucleic acids

C) proteins
D) amylose
E) both phospholipids and nucleic acids

E

If cells are grown in a medium containing radioactive 15N, which of these molecules will be labeled?
A) fatty acids only
B) nucleic acids only

C) proteins only
D) both fatty acids and proteins

E) both proteins and nucleic acids

E

A chemist wishes to make an organic molecule less acidic. Which of the following functional groups should be added to the molecule in order to do so?
A) carboxyl
B) sulfhydryl

C) hydroxyl
D) amino
E) phosphate

D

Which class of biological polymer has the greatest functional variety?

A) polysaccharides
B) proteins
C) DNA

D) RNA

B

A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism is more closely related to

A) humans than to frogs.

B) frogs than to humans.

C) rats than to frogs.
D) humans than to rats.

E) gibbons than to rats.

B

Which functional group is not present in this molecule?

A) carboxyl
B) sulfhydryl
C) hydroxyl
D) amino

B

Which chemical group is most likely to be responsible for an organic molecule behaving as a base (see Concept 2.5)?
A) hydroxyl
B) carbonyl

C) carboxyl
D) amino
E) phosphate

D

Which of the following categories includes all others in the list?

A) monosaccharide
B) disaccharide
C) starch

D) carbohydrate
E) polysaccharide

D

Which of the following statements concerning unsaturated fats is true?

A) They are more common in animals than in plants.
B) They have double bonds in the carbon chains of their fatty acids.
C) They generally solidify at room temperature.

D) They contain more hydrogen than do saturated fats having the same number of carbon atoms.

E) They have fewer fatty acid molecules per fat molecule.

B

The structural level of a protein least affected by a disruption in hydrogen bonding is the

A) primary level.
B) secondary level.
C) tertiary level.

D) quaternary level.
E) All structural levels are equally affected.

A

Which of the following hydrocarbons has a double bond in its carbon skeleton?

A) C3H8
B) C2H6
C) CH4

D) C2H4

E) C2H2

D

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions?
A) C60H120O60
B) C6H12O6

C) C60H102O51

D) C60H100O50

E) C60H111O51

C

When biologists wish to study the internal ultrastructure of cells, they can achieve the finest resolution by using a
A) phase-contrast light microscope.
B) scanning electron microscope.

C) transmission electronic microscope.
D) confocal fluorescence microscope.
E) super-resolution fluorescence microscope.

C

The advantage of light microscopy over electron microscopy is that
A) light microscopy provides for higher magnification than electron microscopy.

B) light microscopy provides for higher resolving power than electron microscopy.

C) light microscopy allows one to view dynamic processes in living cells.
D) light microscopy provides higher contrast than electron microscopy.
E) specimen preparation for light microcopy does not produce artifacts.

C

A primary objective of cell fractionation is to

A) view the structure of cell membranes.
B) sort cells based on their size and weight.
C) determine the size of various organelles.

D) separate the major organelles so that their particular functions can be determined.

E) separate lipid-soluble from water-soluble molecules.

D

In the fractionation of homogenized cells using centrifugation, the primary factor that determines whether a specific cellular component ends up in the supernatant or the pellet is

A) the relative solubility of the component.
B) the size and weight of the component.

C) the percentage of carbohydrates in the component.
D) the presence or absence of nucleic acids in the component.

E) the presence or absence of lipids in the component.

B

Which of the following correctly lists the order in which cellular components will be found in the pellet when homogenized cells are treated with increasingly rapid spins in a centrifuge?
A) ribosomes, nucleus, mitochondria
B) chloroplasts, ribosomes, vacuoles

C) nucleus, ribosomes, chloroplasts

D) vacuoles, ribosomes, nucleus
E) nucleus, mitochondria, ribosomes

E

What is the reason that a modern electron microscope (TEM) can resolve biological images to the subnanometer level, as opposed to the tens of nanometers achievable for the best super- resolution light microscope?
A) The focal length of the electron microscope is significantly longer.

B) Contrast is enhanced by staining with atoms of heavy metal.
C) Electron beams have much shorter wavelengths than visible light.
D) The electron microscope has a much greater ratio of image size to real size.

E) The electron microscope cannot image whole cells at one time.

C

What technique would be most appropriate to use to observe the movements of condensed chromosomes during cell division?
A) standard light microscopy
B) scanning electron microscopy

C) transmission electron microscopy
D) confocal fluorescence microscopy
E) super-resolution fluorescence microscopy

A

The smallest cell structure that would most likely be visible with a standard (not super- resolution) research-grade light microscope is
A) a mitochondrion.
B) a microtubule.

C) a ribosome.
D) a microfilament.
E) a nuclear pore.

A

All of the following are part of a prokaryotic cell except

A) DNA.
B) a cell wall.
C) a plasma membrane.

D) ribosomes.
E) an endoplasmic reticulum.

E

Which of the following is a major cause of the size limits for certain types of cells?

A) limitation on the strength and integrity of the plasma membrane as cell size increases

B) the difference in plasma membranes between prokaryotes and eukaryotes
C) evolutionary progression in cell size; more primitive cells have smaller sizes

D) the need for sufficient surface area to support the cell's metabolic needs

E) rigid cell walls that limit cell size expansion

D

Which of the following statements concerning cells of bacteria and archaea is correct?

A) Archaea contain small membrane-enclosed organelles; bacteria do not.
B) Archaea contain a membrane-bound nucleus; bacteria do not.
C) DNA is present in both archaea and bacteria.

D) DNA is present in the mitochondria of both bacteria and archaea.

A

Prokaryotes are classified as belonging to two different domains. What are the domains?

A) Bacteria and Eukarya
B) Bacteria and Archaea
C) Archaea and Protista

D) Bacteria and Protista
E) Bacteria and Fungi

B

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
A) lipids
B) glycogen

C) proteins
D) cellulose
E) nucleic acids

C

The nuclear lamina is an array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you expect to be the most likely immediate consequence?
A) the loss of all nuclear function

B) the inability of the nucleus to divide during cell division

C) a change in the shape of the nucleus
D) failure of chromosomes to carry genetic information
E) inability of the nucleus to keep out destructive chemicals

C

A cell with a predominance of free ribosomes is most likely

A) producing primarily proteins for secretion.
B) producing primarily cytoplasmic proteins.
C) constructing an extensive cell wall or extracellular matrix.

D) digesting large food particles.

E) enlarging its vacuole.

B

Which structure is the site of the synthesis of proteins that may be exported from the cell?

A) rough ER
B) lysosomes
C) plasmodesmata

D) Golgi vesicles
E) free cytoplasmic ribosomes

A

ECM proteins are made by ribosomes in which part of a eukaryotic cell?

A) mitochondria
B) cytoplasm
C) nuclear envelope

D) Golgi apparatus
E) rough ER

E

The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
A) plant cells are capable of having a much higher surface-to-volume ratio than animal cells.
B) plant cells have a much more highly convoluted (folded) plasma membrane than animal cells.

C) plant cells contain a large vacuole that reduces the volume of the cytoplasm.

D) animal cells are more spherical, whereas plant cells are elongated.
E) plant cells can have lower surface-to-volume ratios than animal cells because plant cells synthesize their own nutrients.

C

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?
A) rough ER
B) smooth ER

C) Golgi apparatus

D) nuclear envelope

E) transport vesicles

B

Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
A) Prokaryotes are unlikely to be able to secrete proteins because they lack an endomembrane system.

B) The mechanism of protein secretion in prokaryotes is probably the same as that in eukaryotes.

C) Proteins that are secreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane.
D) In prokaryotes, the ribosomes that are used for the synthesis of secreted proteins are located outside of the cell.

E) Prokaryotes contain large pores in their plasma membrane that permit the movement of proteins out of the cell.

C

Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
A) ribosome
B) lysosome

C) smooth endoplasmic reticulum

D) mitochondrion
E) contractile vacuole

C

The Golgi apparatus has a polarity or sidedness to its structure and function. Which of the following statements correctly describes this polarity?
A) Transport vesicles fuse with one side of the Golgi and leave from the opposite side.
B) Proteins in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.

C) Lipids in the membrane of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.
D) Soluble proteins in the cisternae (interior) of the Golgi may be sorted and modified as they move from one side of the Golgi to the other.

E) All of the above correctly describe polar characteristics of the Golgi function.

E

The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by
A) the physical separation of most membranes from each other.
B) the transportation of membrane lipids among the endomembrane system by small membrane vesicles.

C) the function of the Golgi apparatus in sorting and directing membrane components.
D) the modification of the membrane components once they reach their final destination.
E) the synthesis of different lipids and proteins in each of the organelles of the endomembrane system.

C

Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. In animal cells, which of the following organelles contains these hydrolytic enzymes?
A) chloroplast
B) lysosome
C) central vacuole
D) peroxisome
E) glyoxysome

B

Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large, complex, undigested lipids. Which cellular organelle must be involved in this condition?
A) the endoplasmic reticulum

B) the Golgi apparatus
C) the lysosome
D) mitochondrion
E) membrane-bound ribosomes

C

Which of the following produces and modifies polysaccharides that will be secreted?

A) lysosome
B) vacuole
C) mitochondrion

D) Golgi apparatus
E) peroxisome

D

One of the key innovations in the evolution of eukaryotes from a prokaryotic ancestor is the endomembrane system. What eukaryotic organelles or features might have evolved as a part of, or as an elaboration of, the endomembrane system?
A) plasma membrane

B) chloroplasts
C) mitochondria
D) nuclear envelope
E) none of these

D

Which of the following contains hydrolytic enzymes?

A) lysosome
B) vacuole
C) mitochondrion

D) Golgi apparatus
E) peroxisome

A

Which organelle often takes up much of the volume of a plant cell?

A) lysosome
B) vacuole
C) mitochondrion

D) Golgi apparatus
E) peroxisome

B

A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
A) a bacterium.
B) an animal, but not a plant.

C) nearly any eukaryotic organism.
D) any multicellular organism, such as a plant or an animal.

E) any kind of organism.

C

Which type of organelle is found in plant cells but not in animal cells?

A) ribosomes
B) mitochondria
C) nuclei

D) plastids
E) none of these

D

Why isn't the mitochondrion classified as part of the endomembrane system?

A) It is a static structure.
B) Its structure is not derived from the ER or Golgi.
C) It has too many vesicles.

D) It is not involved in protein synthesis.
E) It is not attached to the outer nuclear envelope.

B

What types of proteins are not synthesized in the rough ER?

A) endoplasmic reticulum proteins
B) extracellular matrix proteins
C) secreted proteins

D) mitochondrial proteins
E) plasma membrane proteins

D

Which organelle is the primary site of ATP synthesis in eukaryotic cells?

A) lysosome
B) vacuole
C) mitochondrion

D) Golgi apparatus
E) peroxisome

C

Which plant cell organelle contains its own DNA and ribosomes?

A) glyoxysome
B) vacuole
C) mitochondrion

D) Golgi apparatus
E) peroxisome

C

Which animal cell organelle contains enzymes that transfer hydrogen from various substrates to oxygen?
A) lysosome
B) vacuole

C) mitochondrion

D) Golgi apparatus

E) peroxisome

E

Thylakoids, DNA, and ribosomes are all components found in

A) vacuoles.
B) chloroplasts.
C) mitochondria.

D) lysosomes.
E) nuclei.

B

In a plant cell, DNA may be found
A) only in the nucleus.
B) only in the nucleus and mitochondria.
C) only in the nucleus and chloroplasts.
D) in the nucleus, mitochondria, and chloroplasts.
E) in the nucleus, mitochondria, chloroplasts, and peroxisomes.

D

The chemical reactions involved in respiration are virtually identical between prokaryotic and eukaryotic cells. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where is most ATP synthesis likely to occur in prokaryotic cells?
A) in the cytoplasm
B) on the inner mitochondrial membrane
C) on the endoplasmic reticulum
D) on the plasma membrane
E) on the inner nuclear envelope

D

The evolution of eukaryotic cells most likely involved
A) endosymbiosis of an aerobic bacterium in a larger host cell–the endosymbiont evolved into mitochondria.
B) anaerobic archaea taking up residence inside a larger bacterial host cell to escape toxic oxygen–the anaerobic bacterium evolved into chloroplasts.
C) an endosymbiotic fungal cell that evolved into the nucleus.
D) acquisition of an endomembrane system, and subsequent evolution of mitochondria from a portion of the Golgi.

A

In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and
A) combine the hydrogen with water molecules to generate hydrogen peroxide.
B) use the hydrogen to break down hydrogen peroxide.

C) transfer the hydrogen to the mitochondria.
D) transfer the hydrogen to oxygen molecules to generate hydrogen peroxide.

D

How does the cell multiply its peroxisomes?
A) They bud off from the Golgi.
B) They are brought into the cell from the environment.
C) They are built de novo from cytosol materials.
D) They split in two after they become sufficiently large.
E) The cell synthesizes hydrogen peroxide and encloses it in a membrane.

D

Which organelle or structure is absent in plant cells?

A) mitochondria
B) Golgi vesicles
C) microtubules

D) centrosomes
E) peroxisomes

D

Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?
A) sites of energy production in cellular respiration
B) membrane proteins

C) ribosomes
D) cytoskeletal structures
E) cellulose fibers in the cell wall

D

Movement of vesicles within the cell depends on what cellular structures?

A) microtubules and motor proteins
B) actin filaments and microtubules
C) actin filaments and ribosomes

D) centrioles and motor proteins
E) actin filaments and motor proteins

A

Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules?
A) both motile cilia and primary (nonmotile) cilia
B) centrioles only

C) both flagella and motile cilia
D) both basal bodies and primary (nonmotile) cilia

E) both centrioles and basal bodies

C

Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to
A) form cleavage furrows during cell division.
B) migrate by amoeboid movement.

C) separate chromosomes during cell division. D) extend pseudopods.
E) maintain the shape of the nucleus.

C

Centrioles, cilia, flagella, and basal bodies have remarkably similar structural elements and arrangements. Which of the following hypotheses is most plausible in light of such structural similarities?
A) Cilia and flagella arise from the centrioles.

B) Loss of basal bodies should lead to loss of all cilia, flagella, and centrioles.
C) Motor proteins such as dynein must have evolved before any of these four kinds of structures.

D) Cilia and flagella coevolved in the same ancestral eukaryotic organism.
E) Natural selection for cell motility repeatedly selected for microtubular arrays in circular patterns in the evolution of each of these structures.

A

Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to
A) perform amoeboid movement.
B) form cleavage furrows.

C) contract muscle fibers.
D) extend pseudopodia.
E) move vesicles around the cell.

E

Which of the following statements about the cytoskeleton is true?
A) The dynamic aspect of cytoskeletal function is made possible by the assembly and disassembly of a large variety of proteins into complex aggregates.
B) Microfilaments are structurally rigid and resist compression, whereas microtubules resist tension (stretching).
C) Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
D) Chemicals that block the assembly of the cytoskeleton would cause little effect on the cell's response to external signals and stimuli.
E) Transport vesicles among the membranes of the endomembrane system produce the cytoskeleton.

C

Cells require which of the following to form cilia or flagella?

A) tubulin
B) laminin
C) actin

D) intermediate filaments
E) secretory vesicles

A

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its
A) nuclear lamina and nuclear matrix.
B) nuclear matrix and extracellular matrix.

C) mitochondria and Golgi apparatus.
D) Golgi apparatus and extracellular matrix.

E) nuclear pores and secretory vesicles.

D

All of the following serve an important role in determining or maintaining the structure of plant cells. Which of the following are distinct from the others in their composition?
A) microtubules
B) microfilaments

C) plant cell walls
D) intermediate filaments
E) nuclear lamina

C

What do the cell walls of plants and the extracellular matrix of animal cells have in common?
A) They are largely composed of phospholipids and glycoproteins.
B) Their proteins are made by free cytoplasmic ribosomes.

C) They form rigid structures that provide structural support for cells but limit their expansion.

D) They limit the passage of small molecules.
E) They have functional connections with the cytoskeleton inside the cell.

E

The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
A) They must block water and small molecules in order to regulate the exchange of matter and energy with their environment.

B) They must permit information transfer between the cell's cytoplasm and the nucleus.
C) They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume.
D) They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.
E) They are composed of a mixture of lipids and carbohydrates.

D

When a potassium ion (K+) moves from the soil into the vacuole of a cell on the surface of a root, it must pass through several cellular structures. Which of the following correctly describes the order in which these structures will be encountered by the ion?
A) plasma membrane → primary cell wall → cytoplasm → vacuole

B) secondary cell wall → plasma membrane → primary cell wall → cytoplasm → vacuole C) primary cell wall → plasma membrane → cytoplasm → vacuole
D) primary cell wall → plasma membrane → lysosome → cytoplasm → vacuole
E) primary cell wall → plasma membrane → cytoplasm → secondary cell wall → vacuole

C

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following? A) gap junctions
B) the nucleus

C) DNA and RNA

D) integrins
E) plasmodesmata

D

Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?
A) peroxisomes
B) desmosomes

C) gap junctions
D) extracellular matrix
E) tight junctions

C

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
A) plasmodesmata.
B) intermediate filaments.

C) tight junctions.
D) desmosomes.
E) gap junctions.

E

Which of the following makes it necessary for animal cells, although they have no cell walls, to have intercellular junctions?
A) Cell membranes do not distinguish the types of ions and molecules passing through them.
B) Large molecules, such as proteins and RNA molecules, do not readily get through one, much less two, adjacent cell membranes.

C) Cell-to-cell communication requires physical attachment of one cell to another.
D) Maintenance of tissue integrity and barriers to fluid leakage requires cells to adhere tightly to one another.
E) The relative shapelessness of animal cells requires a mechanism for keeping the cells aligned.

D

Signals from the ECM to the cytoskeleton may be transmitted by

A) fibronectin.
B) proteoglycans.
C) integrins.

D) collagen.
E) middle lamella.

C

The differences among the three categories of cytoskeletal elements outlined in the table above would suggest that each of the following has specialized roles. Which of the following is a correct match? (All three elements are involved in the maintenance of cell shape.)
A) microfilaments and the nuclear lamina
B) microtubules and cleavage furrow formation
C) microfilaments and ciliary motion
D) intermediate filaments and cytoplasmic streaming
E) microtubules and chromosome movement

E

A biologist wants specifically to examine the surfaces of different types of cells in kidney tubules of small mammals. The cells in question can be distinguished by external shape, size, and 3-D characteristics. Which of the following would be the optimum method for her study?
A) transmission electron microscopy
B) cell fractionation
C) light microscopy using stains specific to kidney function
D) light microscopy of living unstained material
E) scanning electron microscopy

E

A newspaper ad for a local toy store indicates that a very inexpensive microscope available for a small child is able to magnify specimens nearly as much as the much more costly microscope available in your college lab. What is the primary reason for the price difference?
A) The ad agency is misrepresenting the ability of the toy microscope to magnify.

B) The toy microscope does not have the same fine control for focus of the specimen.
C) The toy microscope magnifies a good deal, but has low resolution and therefore poor-quality images.
D) The college microscope produces greater contrast in the specimens.
E) The toy microscope usually uses a different wavelength of light source.

C

A biologist ground up some plant leaf cells and then centrifuged the mixture to fractionate the organelles. Organelles in one of the heavier fractions could produce ATP in the light, whereas organelles in the lighter fraction could produce ATP in the dark. The heavier and lighter fractions are most likely to contain, respectively,

A) mitochondria and chloroplasts.

B) chloroplasts and peroxisomes.

C) peroxisomes and chloroplasts.

D) chloroplasts and mitochondria.

E) mitochondria and peroxisomes.

D

Which structure is not part of the endomembrane system?

A) nuclear envelope
B) chloroplast
C) Golgi apparatus

D) plasma membrane
E) ER

B

Which structure is common to plant and animal cells?

A) chloroplast
B) wall made of cellulose
C) central vacuole

D) mitochondrion
E) centriole

D

Which of the following is present in a prokaryotic cell?

A) mitochondrion
B) ribosome
C) nuclear envelope

D) chloroplast
E) ER

B

Which structure-function pair is mismatched? A) nucleolus; production of ribosomal subunits B) lysosome; intracellular digestion
C) ribosome; protein synthesis

D) Golgi; protein trafficking
E) microtubule; muscle contraction

E

Cyanide binds to at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the
A) mitochondria.
B) ribosomes.

C) peroxisomes.
D) lysosomes.
E) endoplasmic reticulum.

A

What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?
A) ER → Golgi → nucleus
B) Golgi → ER → lysosome

C) nucleus → ER → Golgi
D) ER → Golgi → vesicles that fuse with plasma membrane
E) ER → lysosomes → vesicles that fuse with plasma membrane

D

Which cell would be best for studying lysosomes?

A) muscle cell
B) nerve cell
C) phagocytic white blood cell

D) leaf cell of a plant
E) bacterial cell

C

Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At high temperatures, these regions
A) are more fluid than the surrounding membrane.
B) are less fluid than the surrounding membrane.

C) are able to flip from inside to outside.
D) detach from the plasma membrane and clog arteries.
E) have higher rates of lateral diffusion of lipids and proteins into and out of these regions.

B

Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes

A) are a phospholipid bilayer.
B) are a phospholipid bilayer between two layers of hydrophilic proteins.
C) are a single layer of phospholipids and proteins.

D) consist of protein molecules embedded in a fluid bilayer of phospholipids.

E) consist of a mosaic of polysaccharides and proteins.

D

Which of the following types of molecules are the major structural components of the cell membrane?
A) phospholipids and cellulose
B) nucleic acids and proteins

C) phospholipids and proteins

D) proteins and cellulose
E) glycoproteins and cholesterol

C

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that
A) the integral membrane proteins are not strong enough to hold the bilayer together.
B) water that is present in the middle of the bilayer freezes and is easily fractured.

C) hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing.

D) the carbon-carbon bonds of the phospholipid tails are easily broken.
E) the hydrophobic interactions that hold the membrane together are weakest at this point.

E

The presence of cholesterol in the plasma membranes of some animals
A) enables the membrane to stay fluid more easily when cell temperature drops.
B) enables the animal to remove hydrogen atoms from saturated phospholipids.
C) enables the animal to add hydrogen atoms to unsaturated phospholipids.
D) makes the membrane less flexible, allowing it to sustain greater pressure from within the cell.

E) makes the animal more susceptible to circulatory disorders.

A

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
A) They can move laterally along the plane of the membrane.
B) They frequently flip-flop from one side of the membrane to the other.

C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
D) They are free to depart from the membrane and dissolve in the surrounding solution.
E) They have hydrophilic tails in the interior of the membrane.

A

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?
A) by increasing the percentage of unsaturated phospholipids in the membrane
B) by increasing the percentage of cholesterol molecules in the membrane

C) by decreasing the number of hydrophobic proteins in the membrane

D) by cotransport of glucose and hydrogen
E) by using active transport

A

In order for a protein to be an integral membrane protein it would have to be

A) hydrophilic.
B) hydrophobic.
C) amphipathic, with at least one hydrophobic region.

D) completely covered with phospholipids.
E) exposed on only one surface of the membrane.

C

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
A) peripheral proteins.

B) phospholipids.
C) carbohydrates.
D) integral proteins.
E) cholesterol molecules.

D

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

B) Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in their membranes.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.

E) The double bonds result in shorter fatty acid tails and thinner membranes.

A

Which of the following is true of integral membrane proteins?

A) They lack tertiary structure.
B) They are loosely bound to the surface of the bilayer.
C) They are usually transmembrane proteins.

D) They are not mobile within the bilayer.
E) They serve only a structural role in membranes.

C

The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is
A) to facilitate diffusion of molecules down their concentration gradients.
B) to actively transport molecules against their concentration gradients.

C) to maintain the integrity of a fluid mosaic membrane.

D) to maintain membrane fluidity at low temperatures.

E) to mediate cell-to-cell recognition.

E

A protein that spans the phospholipid bilayer one or more times is

A) a transmembrane protein.
B) an integral protein.
C) a peripheral protein.

D) an integrin.
E) a glycoprotein.

A

Which of these are not embedded in the hydrophobic portion of the lipid bilayer?

A) transmembrane proteins
B) integral proteins
C) peripheral proteins

D) integrins
E) glycoproteins

C

The cell membranes of Antarctic ice fish might have which of the following adaptations?

A) very long chain fatty acids
B) branched isoprenoid lipids
C) a high percentage of polyunsaturated fatty acids

D) a higher percentage of trans fatty acids E) no cholesterol

C

The formulation of a model for a structure or for a process serves which of the following purposes?
A) It asks a scientific question.
B) It functions as a testable hypothesis.

C) It records observations.
D) It serves as a data point among results.
E) It can only be arrived at after years of experimentation.

B

Why are lipids and proteins free to move laterally in membranes?
A) The interior of the membrane is filled with liquid water.
B) Lipids and proteins repulse each other in the membrane.
C) Hydrophilic portions of the lipids are in the interior of the membrane.
D) There are only weak hydrophobic interactions in the interior of the membrane. E) Molecules such as cellulose can pull them in various directions.

D

Over the years, the fluid mosaic model has been refined based on recent experimental findings. In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?
A) The membrane is only fluid across a very narrow temperature range.
B) Proteins rarely move in the membrane.
C) Unsaturated lipids are excluded from the membranes and do not contribute to membrane fluidity.
D) The concentration of protein molecules appears to be much higher.
E) Membrane proteins are made of only acidic amino acids.

D

Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
A) Because the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical

B) Because cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical.
C) The two sides of a cell membrane face different environments and carry out different functions.

D) The chemical constitution of the inner and outer layer of the cell membrane is predetermined by genes.
E) Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane’s asymmetrical nature.

C

Which of the following is true for the evolution of cell membranes?
A) The fluid mosaic nature of cell membranes provides the explanation for the evolution of cell membranes.
B) Membrane proteins are the sole component responsible for the evolution of cell membranes.

C) The evolution of cell membranes is driven by the evolution of glycoproteins and glycolipids.

D) All components of membranes evolve as a result of natural selection.
E) An individual organism selects its preferred type of cell membrane for particular functions.

D

The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an example of

A) diffusion across the lipid bilayer.

B) facilitated diffusion.
C) active transport.
D) osmosis.

E) cotransport.

A

What kinds of molecules pass through a cell membrane most easily?

A) large and hydrophobic
B) small and hydrophobic
C) large polar

D) ionic
E) monosaccharides such as glucose

B

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

A) It is a peripheral membrane protein.
B) It exhibits a specificity for a particular type of molecule.
C) It requires the expenditure of cellular energy to function.

D) It works against diffusion.
E) It has few, if any, hydrophobic amino acids.

B

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
A) CO2
B) an amino acid

C) glucose

D) K+
E) starch

A

Which of the following statements is correct about diffusion?
A) It is very rapid over long distances.
B) It requires an expenditure of energy by the cell.
C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
E) It requires integral proteins in the cell membrane.

C

Water passes quickly through cell membranes because

A) the bilayer is hydrophilic.
B) it moves through hydrophobic channels.
C) water movement is tied to ATP hydrolysis.

D) it is a small, polar, charged molecule.
E) it moves through aquaporins in the membrane.

E

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that

A) the fresh water and the salt solution are both hypertonic to the cells of the celery stalks.
B) the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.
C) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.

D) the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks.

E) the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks.

C

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?
A) Water will leave the cells, causing them to shrivel and collapse.
B) NaCl will be exported from the red blood cells by facilitated diffusion.

C) The blood cells will take up water, swell, and eventually burst.
D) NaCl will passively diffuse into the red blood cells.
E) The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

A

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
A) The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution.
B) The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution. C) The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution.

D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.

E) The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.

D

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
A) The cell will burst.
B) The cell membrane will lyse.

C) Plasmolysis will shrink the interior.

D) The cell will become flaccid.
E) The cell will become turgid.

E

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

A) simple diffusion
B) phagocytosis
C) active transport pumps D) exocytosis
E) facilitated diffusion

E

Which of the following membrane activities requires energy from ATP hydrolysis?

A) facilitated diffusion of chloride ions across the membrane through a chloride channel B) movement of water into a cell

C) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell
E) movement of carbon dioxide out of a paramecium

C

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A) Sodium and glucose compete for the same binding site in the cotransporter.
B) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.

C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
D) The cotransporter can also transport potassium ions.
E) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

E

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane–more acidic outside the cell than inside the cell. Phosphate transport is an example of

A) passive diffusion.
B) facilitated diffusion.
C) active transport.
D) osmosis.
E) cotransport.

E

What is the voltage across a membrane called?

A) water potential
B) chemical gradient
C) membrane potential

D) osmotic potential
E) electrochemical gradient

C

The sodium-potassium pump is called an electrogenic pump because it

A) pumps equal quantities of Na+ and K+ across the membrane. B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.

E) is used to drive the transport of other molecules against a concentration gradient.

C

The movement of potassium into an animal cell requires

A) low cellular concentrations of sodium.
B) high cellular concentrations of potassium.
C) an energy source such as ATP.

D) a cotransport protein.
E) a potassium channel protein.

C

Ions diffuse across membranes through specific ion channels

A) down their chemical gradients.
B) down their concentration gradients.
C) down the electrical gradients.

D) down their electrochemical gradients.

E) down the osmotic potential gradients.

D

Which of the following would increase the electrochemical gradient across a membrane?

A) a chloride channel
B) a sucrose-proton cotransporter
C) a proton pump

D) a potassium channel
E) both a proton pump and a potassium channel

C

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?
A) Proton pumps must have evolved before any living organisms were present on Earth.
B) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.

C) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
D) Cells of each domain evolved proton pumps independently when oceans became more acidic.

E) Proton pumps are necessary to all cell membranes.

B

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
A) peroxisomes.
B) lysosomes.

C) Golgi vesicles.
D) vacuoles.
E) secretory vesicles.

B

Familial hypercholesterolemia is characterized by which of the following?
A) defective LDL receptors on the cell membranes
B) poor attachment of the cholesterol to the extracellular matrix of cells
C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes D) inhibition of the cholesterol active transport system in red blood cells

E) a general lack of glycolipids in the blood cell membranes

A

The difference between pinocytosis and receptor-mediated endocytosis is that
A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well.
B) pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area.
C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
D) pinocytosis requires cellular energy, but receptor-mediated endocytosis does not.
E) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

C

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
A) on the outside of vesicles
B) on the inside surface of the cell membrane

C) on the inside surface of the vesicle

D) on the outer surface of the nucleus

E) on the ER

C

When protein membrane receptors are activated, what usually happens?

A) A change occurs in intracellular ion concentration.
B) The receptors open and close in response to protein signals.
C) A change occurs on only one membrane surface: exterior or interior.

D) The receptor preferentially binds with lipid or glycolipid signal molecules.

E) The receptor changes conformation after binding with signal polypeptides.

E

Which of the following is true of steroid receptors?
A) The receptor molecules are themselves lipids or glycolipids.
B) The receptor may be inside the nuclear membrane.
C) The unbound steroid receptors are quickly recycled by lysosomes.
D) The concentration of steroid receptors must be relatively high in most cells.

E) The receptor molecules are free to move in and out of most organelles.

B

What is most likely to happen to an animal's target cells that lack receptors for local regulators?
A) They might compensate by receiving nutrients via a factor.
B) They could develop normally in response to neurotransmitters instead.

C) They could divide but never reach full size.
D) They might not be able to multiply in response to growth factors from nearby cells.

E) Hormones would not be able to interact with target cells.

D

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?
A) hormonal signaling
B) autocrine signaling

C) paracrine signaling

D) endocrine signaling

E) synaptic signaling

C

In which of the following ways do plant hormones differ from hormones in animals? A) Plant hormones interact primarily with intracellular receptors.
B) Plant hormones may travel in air or through vascular systems.
C) Animal hormones are found in much greater concentration.

D) Plant hormones are synthesized from two or more distinct molecules.

E) Animal hormones are primarily for mating and embryonic development.

B

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?
A) receptor
B) relay molecule

C) transducer
D) signal molecule
E) endocrine molecule

D

Testosterone functions inside a cell by
A) acting as a signal receptor that activates tyrosine kinases.
B) binding with a receptor protein that enters the nucleus and activates specific genes.

C) acting as a steroid signal receptor that activates ion channel proteins.
D) becoming a second messenger that inhibits nitric oxide.
E) coordinating a phosphorylation cascade that increases spermatogenesis.

B

Which of the following is true of transcription factors?
A) They regulate the synthesis of DNA in response to a signal.

B) They transcribe ATP into cAMP.
C) They initiate the epinephrine response in animal cells.
D) They control gene expression.
E) They regulate the synthesis of lipids in the cytoplasm.

D

In general, a signal transmitted via phosphorylation of a series of proteins

A) brings a conformational change to each protein.
B) requires binding of a hormone to a cytosol receptor.
C) cannot occur in yeasts because they lack protein phosphatases.

D) requires phosphorylase activity.
E) allows target cells to change their shape and therefore their activity.

A

Which of the following most likely would be an immediate result of a growth factor binding to its receptor?
A) protein kinase activity
B) adenylyl cyclase activity

C) GTPase activity
D) protein phosphatase activity

E) phosphorylase activity

A

Which of the following statements is true of signal molecules?
A) When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.
B) In response to some G-protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.
C) In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and eventually the nucleus.
D) Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal molecule.
E) Protein kinase A activation is one possible result of signal molecules binding to G-protein- coupled receptors.

E

Which of the following is a correct association?
A) kinase activity and the addition of a tyrosine
B) phosphodiesterase activity and the removal of phosphate groups

C) GTPase activity and hydrolysis of GTP to GDP
D) phosphorylase activity and the catabolism of glucose
E) adenylyl cyclase activity and the conversion of cAMP to AMP

C

The function of phosphatases in signal transduction is best described as to
A) move the phosphate group of the transduction pathway to the next molecule of a series.

B) prevent a protein kinase from being reused when there is another extracellular signal.

C) amplify the transduction signal so it affects multiple transducers.
D) amplify the second messengers such as cAMP.
E) inactivate protein kinases and turn off the signal transduction.

E

In which of the following ways could signal transduction most probably be explored in research to treat cancer?
A) removal of serine/threonine phosphate acceptors from transduction pathways in colon pre- cancerous growths

B) alteration of protein kinases in cell cycle regulation in order to slow cancer growth
C) increase in calcium ion uptake into the cytoplasm in order to modulate the effects of environmental carcinogens
D) expansion of the role of transduction inhibitors in the cells before they give rise to cancer

E) increase in the concentration of phosphodiesterases in order to produce more AMP

B

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?
A) lower cytoplasmic levels of cAMP
B) an increase in receptor tyrosine kinase activity

C) a decrease in transcriptional activity of certain genes

D) an increase in cytosolic calcium concentration
E) a decrease in G-protein activity

C

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?
A) Estrogen is produced in very large concentration and therefore diffuses widely.
B) Estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding.
C) Estrogen is kept away from the surface of any cells not able to bind it at the surface.
D) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.
E) The subcomponents of estrogen, when metabolized, can influence cell response.

D

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?
A) Growth factor ligands do not bind as efficiently to receptors.

B) Their lower hormone concentrations elicit a lesser response.

C) cAMP levels change very frequently.
D) Enzymatic activity declines.
E) ATP production decreases.

A

Sutherland discovered that the signaling molecule epinephrine
A) brings about a decrease in levels of cAMP as a result of bypassing the plasma membrane.

B) causes lower blood glucose by binding to liver cells.
C) interacts with insulin inside muscle cells.
D) interacts directly with glycogen phosphorylase.
E) elevates cytosolic concentrations of cyclic AMP.

E

Which of the following is the greatest advantage of having multiple steps in a transduction pathway?
A) Many of the steps can be used in multiple pathways.
B) Having multiple steps in a pathway requires the least amount of ATP.

C) Having multiple steps provides for greater possible amplification of a signal.

D) Each individual step can remove excess phosphate groups from the cytoplasm.

E) Each step can be activated by several G proteins simultaneously

C

GTPase activity is important in the regulation of signal transduction because it A) increases the available concentration of phosphate.
B) decreases the amount of G protein in the membrane.
C) hydrolyzes GTP to GDP, thus shutting down the pathway.

D) converts cGMP to GTP.
E) phosphorylates protein kinases.

C

Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins?
A) gap junctions

B) aquaporins
C) electrogenic ion pumps
D) cotransporters
E) hydrophilic channels

E

A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water–equal to the volume of blood lost–is transferred directly into one of his veins. What will be the most probable result of this transfusion?
A) It will have no unfavorable effect as long as the water is free of viruses and bacteria.

B) The patient's red blood cells will shrivel up because the blood fluid has become hypotonic compared to the cells.
C) The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.

D) The patient's red blood cells will shrivel up because the blood fluid has become hypertonic compared to the cells.
E) The patient's red blood cells will burst because the blood fluid has become hypertonic compared to the cells.

C

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
A) blood or tissue type of the patient

B) hydrophobicity of the drug molecule
C) lack of charge on the drug molecule
D) similarity of the drug molecule to other molecules transported by the target cells

E) lipid composition of the target cells' plasma membrane

D

The coupled G protein most likely interacts with this receptor

A) at the NH3 end.
B) at the COO- end.
C) along the exterior margin.

D) along the interior margin.
E) at the loop between H5 and H6.

E

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?
A) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

B) It could activate only the epinephrine system.
C) It would be able to carry out reception and transduction but would not be able to respond to a signal.
D) It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
E) It would employ a transduction pathway directly from an external messenger.

A

In what way do the membranes of a eukaryotic cell vary?
A) Phospholipids are found only in certain membranes.
B) Certain proteins are unique to each kind of membrane.
C) Only certain membranes of the cell are selectively permeable.
D) Only certain membranes are constructed from amphipathic molecules.
E) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.

B

Which of the following factors would tend to increase membrane fluidity?

A) a greater proportion of unsaturated phospholipids
B) a greater proportion of saturated phospholipids
C) a lower temperature

D) a relatively high protein content in the membrane
E) a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

A

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because
A) they are species specific.
B) they always lead to the same cellular response.

C) they amplify the original signal manifold.
D) they counter the harmful effects of phosphatases.

E) the number of molecules used is small and fixed.

C

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because
A) only target cells retain the appropriate DNA segments.
B) intracellular receptors are present only in target cells.

C) most cells lack the Y chromosome required.
D) only target cells possess the cytosolic enzymes that transduce the testosterone.

E) only in target cells is testosterone able to initiate a phosphorylation cascade.

B

Which of the following processes includes all the others?

A) osmosis
B) diffusion of a solute across a membrane
C) facilitated diffusion

D) passive transport
E) transport of an ion down its electrochemical gradient

D

Based on the figure given below, which of these experimental treatments would increase the rate of sucrose transport into the cell?

A) decreasing extracellular sucrose concentration
B) decreasing extracellular pH
C) decreasing cytoplasmic pH
D) adding an inhibitor that blocks regeneration of ATP
E) adding a substance that makes the membrane more permeable to hydrogen ions

B