Why does ice float in liquid water?
A) The high surface tension of liquid water keeps the ice on top.
B) The ionic bonds between the molecules in ice prevent the ice from sinking.
C) Ice always has air bubbles that keep it afloat.
D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
E) The crystalline lattice of ice causes it to be denser than liquid water.

D

Hydrophobic substances such as vegetable oil are
A) nonpolar substances that repel water molecules.
B) nonpolar substances that have an attraction for water molecules.
C) polar substances that repel water molecules.
D) polar substances that have an affinity for water.
E) charged molecules that hydrogen-bond with water molecules.

A

Which of the following statements is true about buffer solutions?
A) They maintain a constant pH when bases are added to them but not when acids are added to them.
B) They maintain a constant pH when acids are added to them but not when bases are added to them.
C) They maintain a relatively constant pH of approximately 7 when either acids or bases are added to them.
D) They maintain a relatively constant pH when either acids or bases are added to them.
E) They are found only in living systems and biological fluids.

D

Basedon your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely
A) positively charged.
B) negatively charged.
C) without charge.
D) hydrophobic.
E) nonpolar.

A

The element present in all organic molecules is
A) hydrogen.
B) oxygen.
C) carbon.
D) nitrogen.
E) phosphorus.

C

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

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

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

The two molecules shown in the figure above are best described as
A) optical isomers.
B) enantiomers.
C) structural isomers.
D) cis-trans isomers.
E) chain length isomers.

C

Organic chemistry is currently defined as
A) the study of compounds made only by living cells.
B) the study of carbon compounds.
C) the study of vital forces.
D) the study of natural (as opposed to synthetic) compounds.
E) the study of hydrocarbons.

B

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

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

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?

1. starch
2. cellulose
3. both starch and cellulose
4. neither starch nor cellulose

A

A molecule with the chemical formula C₆H₁₂O₆ is probably a

1. protein
2. carbohydrate
3. lipid
4. nucleic acid

B

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

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

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

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

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 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

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 affect its biological activity.

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 statements about the 5' end of a polynucleotide strand of DNA 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

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

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

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

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

The molecule shown in Figure 5.3 is a

A) polysaccharide.
B) polypeptide.
C) saturated fatty acid.
D) triacylglycerol.
E) unsaturated fatty acid.

E

Which of the following categories includes all others in the list?
A) monosaccharide
B) disaccharide
C) starch
D) carbohydrate
E) polysaccharide

D

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 pairs of base sequences could form a short stretch of a normal double helix of DNA?
A) 5'-purine-pyrimidine-purine-pyrimidine-3' with 3'-purine-pyrimidine-purine-pyrimidine-5'
B) 5'-AGCT-3' with 5'-TCGA-3'
C) 5'-GCGC-3' with 5'-TATA-3'
D) 5'-ATGC-3' with 5'-GCAT-3'
E) All of these pairs are correct.

D

Which of the following statements is/are true regarding the chemical reaction illustrated in Figure 5.5?
A) It is a hydrolysis reaction.
B) It results in a peptide bond.
C) It joins two fatty acids together.
D) It is a hydrolysis reaction and it results in a peptide bond.
E) It is a hydrolysis reaction, it results in a peptide bond, and it joins two fatty acids together.

B

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 a surface area of sufficient area to support the cell's metabolic needs
E) rigid cell walls that limit cell size expansion

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 evolved into the nucleus.
D) acquisition of an endomembrane system, and subsequent evolution of mitochondria from a portion of the Golgi.

A

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 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

Which type or organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?

1. ribosome
2. lysosome
3. smooth endoplasmic reticulum
4. mitochondrion

C

Which structure is the site of the synthesis of proteins that will likely become part of the cell membrane?

1. rough ER
2. lysosomes
3. plasmodesmata
4. Golgi vesicles

A

Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. Which of the following organelles contains these hydrolytic enzymes in animal cells?

1. chloroplast
2. lysosome
3. central vacuole
4. peroxisome

B

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 organelle often takes up much of the volume of a plant cell?
A) lysosome
B) vacuole
C) mitochondrion
D) Golgi apparatus
E) peroxisome

B

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

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

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

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, like a plant or an animal.
E) any kind of organism.

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?

1. lysosome; intracellular digestion
2. ribosome; protein synthesis
3. chloroplast; ATP production
4. nucleolus; production of ribosomal subunits

C

Cyanide binds with 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 lyosomes?
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. As a result, these lipid rafts
A) are more fluid than the surrounding membrane.
B) are more rigid 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 the lipid rafts.

B

Singer and Nicolson's fluid mosaic model of the membrane proposed that
A) membranes are a phospholipid bilayer.
B) membranes are a phospholipid bilayer between two layers of hydrophilic proteins.
C) membranes are a single layer of phospholipids and proteins.
D) membranes consist of protein molecules embedded in a fluid bilayer of phospholipids.
E) membranes consist of a mosaic of polysaccharides and proteins.

D

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 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 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

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

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

Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of
A) diffusion across the lipid bilayer.
B) facilitated diffusion.
C) active transport.
D) osmosis.
E) cotransport.

A

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

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 is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A) The sodium ions are moving down their electrochemical gradient while glucose is moving up.
B) Glucose entering the cell along 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 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

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
A) It will be on the cytoplasmic side of the ER.
B) It will be on the side facing the interior of the ER.
C) It could be facing in either direction because proteins are properly reoriented in the Golgi apparatus.
D) It doesn't matter, because the pump is not active in the ER.

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

White blood cells engulf bacteria through what process?

1. exocytosis
2. phagocytosis
3. pinocytosis
4. osmosis

B

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

1. peroxisomes
2. lysosomes
3. Golgi vesicles
4. vacuoles

B

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?

1. The patient's red blood cells will burst because the blood fluid has become hypertonic compared to the cells.
2. The patient's red blood cells will shrivel up because the blood fluid has become hypotonic compared to the cells.
3. The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
4. The patient's red blood cells will shrivel up because the blood fluid has become hypertonic compared to tech cells.

C

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 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

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
A) spread in a continuous layer over the inner and outer surfaces of the membrane.
B) confined to the hydrophobic interior of the membrane.
C) embedded in a lipid bilayer.
D) randomly oriented in the membrane, with no fixed inside-outside polarity.
E) free to depart from the fluid membrane and dissolve in the surrounding solution.

C

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

Which of the following processes includes all 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 above, which of these experimental treatments would increase the rate of sucrose transport into the cell?

1. decreasing extracellular sucrose concentration
2. increasing extracellular H⁺
3. increasing cytoplasmic H⁺
4. adding an inhibitor that blocks the regeneration of ATP

B

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
A) catalysis
B) metabolism
C) anabolism
D) dehydration
E) catabolism

E

Which of the following is (are) true for anabolic pathways?
A) They do not depend on enzymes.
B) They are usually highly spontaneous chemical reactions.
C) They consume energy to build up polymers from monomers.
D) They release energy as they degrade polymers to monomers.
E) They consume energy to decrease the entropy of the organism and its environment.

C

Which of the following is an example of potential rather than kinetic energy?
A) the muscle contractions of a person mowing grass
B) water rushing over Niagara Falls
C) light flashes emitted by a firefly
D) a molecule of glucose
E) the flight of an insect foraging for food

D

Which of the following is true for all exergonic reactions?
A) The products have more total energy than the reactants.
B) The reaction proceeds with a net release of free energy.
C) The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.
D) A net input of energy from the surroundings is required for the reactions to proceed.
E) The reactions are rapid.

B

A chemical reaction that has a positive ΔG is correctly described as
A) endergonic.
B) endothermic.
C) enthalpic.
D) spontaneous.
E) exothermic.

A

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?
A) -40 kcal/mol
B) -20 kcal/mol
C) 0 kcal/mol
D) +20 kcal/mol
E) +40 kcal/mol

B

Why is ATP an important molecule in metabolism?

1. its hydrolysis provides an input of free energy for exergonic reactions
2. it provides energy coupling between exergonic and endergonic reactions
3. it is one of the four building blocks for DNA synthesis
4. Its terminal phosphate bond has lower energy than the other two

B

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

1. entropy
2. activation energy
3. endothermic level
4. equilibrium point

B

Which of the following is true of enzymes?
A) Nonprotein cofactors alter the substrate specificity of enzymes.
B) Enzyme function is increased if the 3-D structure or conformation of an enzyme is altered.
C) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.
D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
E) Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.

D

The active site of an enzyme is the region that

1. binds allosteric activators of the enzyme
2. is involved in the catalytic reaction of the enzyme
3. binds noncompetitive inhibitors of the enzyme
4. is inhibited by the presence of a coenzyme or a cofactor

B

According the the induced fit hypothesis of enzyme catalysis, which of the following is correct?

1. the binding of the substrate depends on the shape of the active site
2. some enzyme change their structure when activators bind to the enzyme
3. a competitive inhibitor can outcompete the substrate for the active site
4. the binding of the substrate changes the shape of the enzymes active site

D

Which of the following statements describes enzyme cooperativity?
A) A multienzyme complex contains all the enzymes of a metabolic pathway.
B) A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway.
C) A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits.
D) Several substrate molecules can be catalyzed by the same enzyme.
E) A substrate binds to an active site and inhibits cooperation between enzymes in a pathway.

C

When you have a severe fever, what grave consequence may occur if the fever is not controlled?
A) destruction of your enzymes' primary structure
B) removal of amine groups from your proteins
C) change in the tertiary structure of your enzymes
D) removal of the amino acids in active sites of your enzymes
E) binding of your enzymes to inappropriate substrates

C

For the enzyme-catalyzed reaction shown in the figure, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?
A) doubling the activation energy needed
B) cooling the reaction by 10°C
C) doubling the concentration of the reactants to 2.0 micromolar
D) doubling the enzyme concentration
E) increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2

D

In the figure, why does the reaction rate plateau at higher reactant concentrations?
A) Feedback inhibition by product occurs at high reactant concentrations.
B) Most enzyme molecules are occupied by substrate at high reactant concentrations.
C) The reaction nears equilibrium at high reactant concentrations.
D) The activation energy for the reaction increases with reactant concentration.
E) The rate of the reverse reaction increases with reactant concentration.

B

Increasing the substrate concentration in an enzymatic reaction would overcome which of the following?

1. denaturization of the enzyme
2. allosteric inhibition
3. competitive inhibition
4. saturation of the enzyme activity

C

Which curve(s) on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?
A) curves 1 and 5
B) curves 2 and 4
C) curves 2 and 5
D) curves 3 and 4
E) curves 3 and 5

E

Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?
A) curves 1 and 4
B) curves 1 and 5
C) curves 2 and 4
D) curves 2 and 5
E) curves 3 and 4

A

how does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

1. by binding at the active site of the enzyme
2. by changing the shape of the enzymes active site
3. by changing the free energy change of the reaction
4. by acting as a coenzyme for the reaction

B

Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses?
A) in or near the active site
B) at an allosteric site
C) at a cofactor binding site
D) in regions of the protein that determine packaging into the virus capsid
E) such mutations could occur anywhere with equal probability

A

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as
A) metabolic inhibition.
B) feedback inhibition.
C) allosteric inhibition.
D) noncooperative inhibition.
E) reversible inhibition.

B

Allosteric enzyme regulation is usually associated with
A) lack of cooperativity.
B) feedback inhibition.
C) activating activity.
D) an enzyme with more than one subunit.
E) the need for cofactors.

D

How might an amino acid change at a site distant from the active site of the enzyme alter the enzyme's substrate specificity?
A) by changing the enzyme's stability
B) by changing the enzyme's location in the cell
C) by changing the shape of the protein
D) by changing the enzyme's pH optimum
E) an amino acid change away from the active site cannot alter the enzyme's substrate specificity

C

Which of the following terms best describes the forward reaction in Figure 8.1?
A) endergonic, ∆G > 0
B) exergonic, ∆G < 0
C) endergonic, ∆G < 0
D) exergonic, ∆G > 0
E) chemical equilibrium, ∆G = 0

B

Which of the following represents the ΔG of the reaction in Figure 8.1?
A) a
B) b
C) c
D) d
E) e

D

Which of the following in Figure 8.1 would be the same in either an enzyme-catalyzed or a noncatalyzed reaction?
A) a
B) b
C) c
D) d
E) e

D

Which of the following represents the activation energy needed for the enzyme-catalyzed reverse reaction, C + D → A + B, in Figure 8.1?
A) a
B) b
C) c
D) d
E) e

A

Which of the following represents the activation energy required for a noncatalyzed reaction in Figure 8.1?
A) a
B) b
C) c
D) d
E) e

C

Which of the following is the most correct interpretation of the figure?
A) Inorganic phosphate is created from organic phosphate.
B) Energy from catabolism can be used directly for performing cellular work.
C) ADP + Pi are a set of molecules that store energy for catabolism.
D) ATP is a molecule that acts as an intermediary to store energy for cellular work.
E) Pi acts as a shuttle molecule to move energy from ATP to ADP.

D

Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid.

Based on this information, which of the following is correct?
A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate.
B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate.
C) Succinate is the substrate, and fumarate is the product.
D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor.
E) Malonic acid is the product, and fumarate is a competitive inhibitor.

Answer: C

C

What is malonic acid's role with respect to succinate dehydrogenase?
A) It is a competitive inhibitor.
B) It blocks the binding of fumarate.
C) It is a noncompetitive inhibitor.
D) It is able to bind to succinate.
E) It is an allosteric regulator.

A

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.

What is substance X?
A) a coenzyme
B) an allosteric inhibitor
C) a substrate
D) an intermediate
E) the product

C

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.

With respect to the enzyme that converts X to Y, substance A functions as
A) a coenzyme.
B) an allosteric inhibitor.
C) the substrate.
D) an intermediate.
E) a competitive inhibitor.

B

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.
A) exergonic; spontaneous
B) exergonic; endergonic
C) free energy; entropy
D) work; energy
E) entropy; enthalpy

B

1) When the temperature of the outside air exceeds their internal body temperature, jackrabbits living in hot, arid lands will
A) dilate the blood vessels in their large ears to transfer more body heat to the environment.
B) constrict the blood vessels in their large ears to reduce transfer of external heat to the blood in their ears.
C) increase motor movements to find a sunny area to maximize heat transfer into their bodies.
D) increase pigmentation in their ears, darkening them to maximize their capacity to take up heat.
E) begin involuntary shivering of their skeletal muscles in order to generate more metabolic heat.

B

2) If thermoregulation is considered to be a secondary function of the large ears of jackrabbits, then the primary function of the ears is
A) to optimize nutrient intake through the thin, permeable surfaces on the ears.
B) to alter the rate of gas exchange, based on the adjustable radius of the ears' blood vessels.
C) to detect predators by using the large size and flexible positioning of the external ears to channel sound waves into the ear canal.
D) to protect offspring from bright sunlight by the positioning of the ears to cast the maximum shadows.
E) to protect against pathogens by having a thick, waxy surface on the ears.

C

40) The body's automatic tendency to maintain a constant and optimal internal environment is termed
A) balanced equilibrium.
B) physiological chance.
C) homeostasis.
D) static equilibrium.
E) estivation.

C

45) To prepare flight muscles for use on a cool morning, hawkmouth moths
A) relax the muscles completely until after they launch themselves into the air.
B) decrease their standard metabolic rate.
C) rapidly contract and relax these muscles to generate metabolic warmth.
D) walk to shaded areas to avoid direct sunlight.
E) reduce the metabolic rate of the muscles to rest them before flight.

C

46) In a survivably cold environment, an ectotherm is more likely to survive an extended period of food deprivation than would an equally sized endotherm because the ectotherm
A) maintains a higher basal metabolic rate.
B) expends more energy per kg of body mass than does the endotherm.
C) invests little energy in temperature regulation.
D) metabolizes its stored energy more readily than can the endotherm.
E) has greater insulation on its body surface.

C

47) Humans can lose, but cannot gain, heat through the process of
A) conduction.
B) convection.
C) radiation.
D) evaporation.
E) metabolism.

D

48) An example of an ectothermic organism that has few or no behavioral options when it comes to its ability to adjust its body temperature is a
A) terrestrial lizard.
B) sea star, a marine invertebrate.
C) bluefin tuna, a predatory fish.
D) hummingbird.
E) honeybee in a hive.

B

50) Endothermy
A) is a characteristic of most animals found in tropical zones.
B) is a characteristic of animals that have a fairly constant body temperature.
C) is a term equivalent to cold-blooded.
D) is a characteristic of mammals but not of birds.
E) is seen only in insects and in certain predatory fishes.

B

54) The temperature-regulating center of vertebrate animals is located in the
A) medulla oblongata.
B) thyroid gland.
C) hypothalamus.
D) subcutaneous layer of the skin.
E) liver.

C

64) Hibernation and estivation during seasons of environmental stress are both examples of
A) acclimatization.
B) torpor.
C) evaporative cooling.
D) nonshivering thermogenesis.
E) shivering thermogenesis.

B

65) Panting by an overheated dog achieves cooling by
A) acclimatization.
B) torpor.
C) evaporation.
D) nonshivering thermogenesis.
E) shivering thermogenesis.

C

68) The thin horizontal arrows in the figure above show that
A) the warmer arterial blood can bypass the legs as needed, when the legs are too cold to function well.
B) the warmer venous blood transfers heat to the cooler arterial blood.
C) the warmer arterial blood transfers heat to the cooler venous blood.
D) the arterial blood is always cooler in the abdomen, compared to the temperature of the venous blood in the feet of the goose.
E) the goose's legs get progressively warmer as the blood moves away from the abdomen to the feet.

C

69) Examine the figure above. Near a goose's abdomen, the countercurrent arrangement of the arterial and venous blood vessels causes
A) the temperature difference between the contents of the two sets of vessels to be minimized.
B) the venous blood to be as cold near the abdomen as it is near the feet.
C) the blood in the feet to be as warm as the blood in the abdomen.
D) the temperature at the abdomen to be less than the temperature at the feet.
E) the loss of the maximum possible amount of heat to the environment.

A

73) Consider the energy budgets for a human, an elephant, a penguin, a mouse, and a snake. The ________ would have the highest total annual energy expenditure, and the ________ would have the highest energy expenditure per unit mass.
A) elephant; mouse
B) elephant; human
C) human; penguin
D) mouse; snake
E) penguin; mouse

A

74) Compared with a smaller cell, a larger cell of the same shape has
A) less surface area.
B) less surface area per unit of volume.
C) the same surface-to-volume ratio.
D) a smaller average distance between its mitochondria and the external source of oxygen.
E) a smaller cytoplasm-to-nucleus ratio.

B

76) You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm?
A) You know from its high and stable body temperature that it must be an endotherm.
B) You know that it is an ectotherm because it is not a bird or mammal.
C) You subject this reptile to various temperatures in the lab and find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm.
D) You note that its environment has a high and stable temperature. Because its body temperature matches the environmental temperature, you conclude that it is an ectotherm.
E) You measure the metabolic rate of the reptile, and because it is higher than that of a related species that lives in temperate forests, you conclude that this reptile is an endotherm and its relative is an ectotherm.

C

Which of the following statements describes the results of this reaction?
C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy
A) C₆H₁₂O₆ is oxidized and O₂ is reduced.
B) O₂ is oxidized and H₂O is reduced.
C) CO₂ is reduced and O₂ is oxidized.
D) C₆H₁₂O₆ is reduced and CO₂ is oxidized.
E) O₂ is reduced and CO₂ is oxidized.

A

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
A) hydrolyzed.
B) hydrogenated.
C) oxidized.
D) reduced.
E) an oxidizing agent.

C

Which of the following statements describes NAD⁺?
A) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
B) NAD⁺ has more chemical energy than NADH.
C) NAD⁺ is oxidized by the action of hydrogenases.
D) NAD⁺ can donate electrons for use in oxidative phosphorylation.
E) In the absence of NAD⁺, glycolysis can still function.

A

Where does glycolysis take place in eukaryotic cells?
A) mitochondrial matrix
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) cytoplasm (cytosol)

B

The ATP made during glycolysis is generated by
A) substrate-level phosphorylation.
B) electron transport.
C) photophosphorylation.
D) chemiosmosis.
E) oxidation of NADH to NAD⁺.

A

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
A) 0%
B) 2%
C) 10%
D) 38%
E) 100%

E

The oxygen consumed during cellular respiration is involved directly in which process or event?
A) glycolysis
B) accepting electrons at the end of the electron transport chain
C) the citric acid cycle
D) the oxidation of pyruvate to acetyl CoA
E) the phosphorylation of ADP to form ATP

B

Which process in eukaryotic cells will proceed normally whether oxygen (O₂) is present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis

B

In addition to ATP, what are the end products of glycolysis?
A) CO₂ and H₂O
B) CO₂ and pyruvate
C) NADH and pyruvate
D) CO₂ and NADH
E) H₂O, FADH₂, and citrate

C

In glycolysis, for each molecule of glucose oxidized to pyruvate
A) two molecules of ATP are used and two molecules of ATP are produced.
B) two molecules of ATP are used and four molecules of ATP are produced.
C) four molecules of ATP are used and two molecules of ATP are produced.
D) two molecules of ATP are used and six molecules of ATP are produced.
E) six molecules of ATP are used and six molecules of ATP are produced.

B

Why is glycolysis described as having an investment phase and a payoff phase?
A) It both splits molecules and assembles molecules.
B) It attaches and detaches phosphate groups.
C) It uses glucose and generates pyruvate.
D) It shifts molecules from cytosol to mitochondrion.
E) It uses stored ATP and then forms a net increase in ATP.

E

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO₂) from one molecule of pyruvate?
A) lactate
B) glyceraldehydes-3-phosphate
C) oxaloacetate
D) acetyl CoA
E) citrate

D

In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + Pi to ATP?
A) energy released as electrons flow through the electron transport system
B) energy released from substrate-level phosphorylation
C) energy released from movement of protons through ATP synthase, against the electrochemical gradient
D) energy released from movement of protons through ATP synthase, down the electrochemical gradient
E) No external source of energy is required because the reaction is exergonic.

D

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
A) It allows for an increased rate of glycolysis.
B) It allows for an increased rate of the citric acid cycle.
C) It increases the surface for oxidative phosphorylation.
D) It increases the surface for substrate-level phosphorylation.
E) It allows the liver cell to have fewer mitochondria.

C

Which of the following normally occurs regardless of whether or not oxygen (O₂) is present?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)

A

The ATP made during fermentation is generated by which of the following?
A) the electron transport chain
B) substrate-level phosphorylation
C) chemiosmosis
D) oxidative phosphorylation
E) aerobic respiration

B

In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
A) ATP, CO₂, and ethanol (ethyl alcohol).
B) ATP, CO₂, and lactate.
C) ATP, NADH, and pyruvate.
D) ATP, pyruvate, and oxygen.
E) ATP, pyruvate, and acetyl CoA.

A

In alcohol fermentation, NAD⁺ is regenerated from NADH by
A) reduction of acetaldehyde to ethanol (ethyl alcohol).
B) oxidation of pyruvate to acetyl CoA.
C) reduction of pyruvate to form lactate.
D) oxidation of ethanol to acetyl CoA.
E) reduction of ethanol to pyruvate.

A

One function of both alcohol fermentation and lactic acid fermentation is to
A) reduce NAD⁺ to NADH.
B) reduce FAD⁺ to FADH₂.
C) oxidize NADH to NAD⁺.
D) reduce FADH₂ to FAD⁺.
E) do none of the above.

C

When skeletal muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by
A) buildup of pyruvate.
B) buildup of lactate.
C) increase in sodium ions.
D) increase in potassium ions.
E) increase in ethanol.

B

Starting with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be made through substrate-level phosphorylation (see Figure 9.2)?

A) 1
B) 2
C) 11
D) 12
E) 24

A

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in Figure 9.2?
A) There will be no change in the levels of oxaloacetate and citric acid.
B) Oxaloacetate will decrease and citric acid will accumulate.
C) Oxaloacetate will accumulate and citric acid will decrease.
D) Both oxaloacetate and citric acid will decrease.
E) Both oxaloacetate and citric acid will accumulate.

C

Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle (see Figure 9.2)?
A) 1 ATP, 2 CO₂, 3 NADH, and 1 FADH₂
B) 2 ATP, 2 CO₂, 3 NADH, and 3 FADH₂
C) 3 ATP, 3 CO₂, 3 NADH, and 3 FADH₂
D) 3 ATP, 6 CO₂, 9 NADH, and 3 FADH₂
E) 38 ATP, 6 CO₂, 3 NADH, and 12 FADH₂

D

For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle (see Figure 9.2), what is the total number of NADH + FADH₂ molecules produced?
A) 4
B) 5
C) 6
D) 10
E) 12

E

Figure 9.3 shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain?
A) oxygen, carbon dioxide, and water
B) NAD⁺, FAD, and electrons
C) NADH, FADH₂, and protons
D) NADH, FADH₂, and O₂
E) oxygen and protons

E

Which of the protein complexes labeled with Roman numerals in Figure 9.3 will transfer electrons to O₂?
A) complex I
B) complex II
C) complex III
D) complex IV
E) All of the complexes can transfer electrons to O₂.

D

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO₂, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.

These three steps result in the formation of
A) acetyl CoA, O₂, and ATP.
B) acetyl CoA, FADH₂, and CO₂.
C) acetyl CoA, FAD, H₂, and CO₂.
D) acetyl CoA, NADH, H⁺, and CO₂.
E) acetyl CoA, NAD⁺, ATP, and CO₂.

D

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If the membranes are agitated further, however, the ability to synthesize ATP is lost.

After the first disruption, when electron transfer and ATP synthesis still occur, what must be present?
A) all of the electron transport proteins as well as ATP synthase
B) all of the electron transport system and the ability to add CoA to acetyl groups
C) the ATP synthase system
D) the electron transport system
E) plasma membranes like those bacteria use for respiration

A

After the further agitation of the membrane vesicles, what must be lost from the membrane?
A) the ability of NADH to transfer electrons to the first acceptor in the electron transport chain
B) the prosthetic groups like heme from the transport system
C) cytochromes
D) ATP synthase, in whole or in part
E) the contact required between inner and outer membrane surfaces

D

What is the oxidizing agent in the following reaction?
Pyruvate + NADH + H⁺ → Lactate + NAD⁺
A) oxygen
B) NADH
C) NAD⁺
D) lactate
E) pyruvate

E

Carbon dioxide (CO₂) is released during which of the following stages of cellular respiration?
A) glycolysis and the oxidation of pyruvate to acetyl CoA
B) oxidation of pyruvate to acetyl CoA and the citric acid cycle
C) the citric acid cycle and oxidative phosphorylation
D) oxidative phosphorylation and fermentation
E) fermentation and glycolysis

B

Where are the proteins of the electron transport chain located?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

C

Energy released by the electron transport chain is used to pump H⁺ into which location in eukaryotic cells?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

D

Where is ATP synthase located in the mitochondrion?
A) cytosol
B) electron transport chain
C) outer membrane
D) inner membrane
E) mitochondrial matrix

D

How many oxygen molecules (O₂) are required each time a molecule of glucose (C₆H₁₂O₆) is completely oxidized to carbon dioxide and water via aerobic respiration,?
A) 1
B) 3
C) 6
D) 12
E) 30

C

Which of the following produces the most ATP when glucose (C₆H₁₂O₆) is completely oxidized to carbon dioxide (CO₂) and water?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)

E

Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C₆H₁₂O₆) in aerobic cellular respiration?
A) 2
B) 4
C) 15
D) 30-32
E) 60-64

E

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
A) CO₂ and glucose
B) H₂O and O₂
C) ADP, Pi, and NADP⁺
D) electrons and H⁺
E) ATP and NADPH

E

Where does the Calvin cycle take place?
A) stroma of the chloroplast
B) thylakoid membrane
C) cytoplasm surrounding the chloroplast
D) interior of the thylakoid (thylakoid space)
E) outer membrane of the chloroplast

A

When oxygen is released as a result of photosynthesis, it is a direct by-product of
A) reducing NADP⁺.
B) splitting water molecules.
C) chemiosmosis.
D) the electron transfer system of photosystem I.
E) the electron transfer system of photosystem II.

B

A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?
A) red and yellow
B) blue and violet
C) green and yellow
D) blue, green, and red
E) green, blue, and yellow

B

Which of the events listed below occurs in the light reactions of photosynthesis?
A) NADP is produced.
B) NADPH is reduced to NADP⁺.
C) Carbon dioxide is incorporated into PGA.
D) ATP is phosphorylated to yield ADP.
E) Light is absorbed and funneled to reaction-center chlorophyll a.

E

Which of the following statements best describes the relationship between photosynthesis and respiration?
A) Respiration runs the biochemical pathways of photosynthesis in reverse.
B) Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.
C) Photosynthesis occurs only in plants and respiration occurs only in animals.
D) ATP molecules are produced in photosynthesis and used up in respiration.
E) Respiration is anabolic and photosynthesis is catabolic.

B

Which statement describes the functioning of photosystem II?
A) Light energy excites electrons in the thylakoid membrane electron transport chain.
B) Photons are passed along to a reaction-center chlorophyll.
C) The P680 chlorophyll donates a pair of protons to NADP⁺, which is thus converted to NADPH.
D) The electron vacancies in P680⁺ are filled by electrons derived from water.
E) The splitting of water yields molecular carbon dioxide as a by-product.

D

Which of the following are directly associated with photosystem I?
A) harvesting of light energy by ATP
B) receiving electrons from the thylakoid membrane electron transport chain
C) generation of molecular oxygen
D) extraction of hydrogen electrons from the splitting of water
E) passing electrons to the thylakoid membrane electron transport chain

B

Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be
A) to determine if they have thylakoids in the chloroplasts.
B) to test for liberation of O₂ in the light.
C) to test for CO₂ fixation in the dark.
D) to do experiments to generate an action spectrum.
E) to test for production of either sucrose or starch.

B

What does the chemiosmotic process in chloroplasts involve?
A) establishment of a proton gradient across the thylakoid membrane
B) diffusion of electrons through the thylakoid membrane
C) reduction of water to produce ATP energy
D) movement of water by osmosis into the thylakoid space from the stroma
E) formation of glucose, using carbon dioxide, NADPH, and ATP

A

Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH 8 solution. What would be likely to happen?
A) The isolated chloroplasts will make ATP.
B) The Calvin cycle will be activated.
C) Cyclic photophosphorylation will occur.
D) The isolated chloroplasts will generate oxygen gas.
E) The isolated chloroplasts will reduce NADP⁺ to NADPH.

A

In a plant cell, where are the ATP synthase complexes located?
A) thylakoid membrane only
B) plasma membrane only
C) inner mitochondrial membrane only
D) thylakoid membrane and inner mitochondrial membrane
E) thylakoid membrane and plasma membrane

D

In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from
A) the stroma to the photosystem II.
B) the matrix to the stroma.
C) the stroma to the thylakoid space.
D) the intermembrane space to the matrix.
E) the thylakoid space to the stroma.

D

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during
A) photosynthesis only.
B) respiration only.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration only.

C

The reactions that produce molecular oxygen (O₂) take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but are not part of photosynthesis.

A

The accumulation of free oxygen in Earth's atmosphere began
A) with the origin of life and respiratory metabolism.
B) with the origin of photosynthetic bacteria that had photosystem I.
C) with the origin of cyanobacteria that had both photosystem I and photosystem II.
D) with the origin of chloroplasts in photosynthetic eukaryotic algae.
E) with the origin of land plants.

C

A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask.
A) The dissolved oxygen in the flask with algae will always be higher.
B) The dissolved oxygen in the flask with algae will always be lower.
C) The dissolved oxygen in the flask with algae will be higher in the light, but the same in the dark.
D) The dissolved oxygen in the flask with algae will be higher in the light, but lower in the dark.
E) The dissolved oxygen in the flask with algae will not be different from the control flask at any time.

D

What is the primary function of the Calvin cycle?
A) use ATP to release carbon dioxide
B) use NADPH to release carbon dioxide
C) split water and release oxygen
D) transport RuBP out of the chloroplast
E) synthesize simple sugars from carbon dioxide

E

A gardener is concerned that her greenhouse is getting too hot from too much light, and seeks to shade her platens with colored translucent plastic sheets. What color should she use to reduce overall light energy, but still maximize plant growth?

1. green
2. blue
3. yellow
4. orange

B

Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?
A) Green and yellow wavelengths inhibit the absorption of red and blue wavelengths.
B) Bright sunlight destroys photosynthetic pigments.
C) Oxygen given off during photosynthesis interferes with the absorption of light.
D) Other pigments absorb light in addition to chlorophyll a.
E) Aerobic bacteria take up oxygen, which changes the measurement of the rate of photosynthesis.

D

What wavelength of light in the figure is most effective in driving photosynthesis?
A) 420 mm
B) 475 mm
C) 575 mm
D) 625 mm
E) 730 mm

A

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?

1. hormonal signaling
2. synaptic signaling
3. paracrine signaling
4. endocrine signaling

C

The function of phosphatases in signal transduction is best described as to

1. prevent a protein kinase from being reused when there is another extracellular signal
2. move the phosphate group of the transduction pathway to the next molecule of a series
3. inactive protein kinases and turn off the signal transduction
4. amplify the transduction signal so it affects multiple transducers

C

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 adenylyl cyclase.
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

Because most receptors are membrane proteins, which of the following is usually true?
A) They lead to changes in intracellular ion concentration.
B) They open and close in response to protein signals.
C) They are only attached to one membrane surface: exterior or interior.
D) They preferentially bind with lipid or glycolipid signal molecules.
E) They change their conformation after binding with signal polypeptides.

E

Which of the following is the best explanation for the fact that most transduction pathways have multiple steps?
A) Most of the steps were already in place because they are steps in other pathways.
B) Multiple steps in a pathway require the least amount of ATP.
C) Multiple steps provide 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

What are scaffolding proteins?
A) ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another
B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores
C) large molecules to which several relay proteins attach to facilitate cascade effects
D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
E) proteins that can reach into the nucleus of a cell to affect transcription

C

Which of the following types of signaling is represented in the figure?
A) autocrine
B) paracrine
C) hormonal
D) synaptic
E) long distance

D

In the figure, the dots in the space between the two structures represent which of the following?
A) receptor molecules
B) signal transducers
C) neurotransmitters
D) hormones
E) pheromones

C

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?
A) receptor tyrosine kinase
B) G protein-coupled receptor
C) phosphorylated receptor tyrosine kinase dimer
D) ligand-gated ion channel
E) intracellular receptor

D

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 the phosphorylation cascade leading to activated transcription factor.

B

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.
A) cAMP
B) G protein
C) GTP
D) adenylyl cyclase
E) G protein-coupled receptor

A

Which of the following sequences correctly represents the flow of electrons during photosynthesis?
A) NADPH → O₂ → CO₂
B) H₂O → NADPH → Calvin cycle
C) NADPH → chlorophyll → Calvin cycle
D) H₂O → photosystem I → photosystem II
E) NADPH → electron transport chain → O₂

B

Which process is most directly driven by light energy?
A) creation of a pH gradient by pumping protons across the thylakoid membrane
B) carbon fixation in the stroma
C) reduction of NADP⁺ molecules
D) removal of electrons from chlorophyll molecules
E) ATP synthesis

D

P680⁺ is said to be the strongest biological oxidizing agent. Why?

1. it is the receptor for the most excited electron in either photosystem
2. it is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system
3. It transfers its electrons to reduce NADP⁺ to NADPH
4. This molecule has a stronger attraction for electrons than oxygen, to obtain electrons from water

D

4) Engulfing-phagocytic cells of innate immunity include all of the following except
A) neutrophils.
B) macrophages.
C) dendritic cells.
D) natural killer cells.

D

6) An inflammation-causing signal released by mast cells at the site of an infection is
A) an interferon.
B) lymphatic fluid.
C) histamine.
D) mucus.
E) sodium ions.

C

11) Antihistamine treatment reduces
A) blood vessel dilation.
B) phagocytosis of antigens.
C) MHC presentation by macrophages.
D) the secondary immune response.
E) clonal selection by antigens.

A

14) The cells and signaling molecules that initiate inflammatory responses are
A) the phagocytes and the lysozymes.
B) the phagocytes and the chemokines.
C) the dendritic cells and the interferons.
D) the mast cells and the histamines.
E) the lymphocytes and the interferons.

D

23) Adaptive immunity depends on
A) traits common to groups of pathogens.
B) pathogen-specific recognition.
C) maternal provision of antibodies to offspring.
D) plants being exposed to new pathogens.
E) having exhausted all options for innate immunity responses.

B

Which statement best describes the difference in responses of effector B cells (plasma cells) and cytotoxic T cells?

1. B cells confer active immunity; cytotoxic T cells confer passive immunity
2. B cells kill pathogens directly; cytotoxic T cells kill host cells
3. B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells.
4. B cells carry out the cell-meditated response; cytotoxic T cells carry out thehumoral response

C

50) Arrange these components of the mammalian immune system as it first responds to a pathogen in the correct sequence.

I. Pathogen is destroyed.
II. Lymphocytes secrete antibodies.
III. Antigenic determinants from pathogen bind to antigen receptors on lymphocytes.
IV. Lymphocytes specific to antigenic determinants from pathogen become numerous.
V. Only memory cells remain.

A) I → III → II → IV → V
B) III → II → I → V → IV
C) II → I → IV → III → V
D) IV → II → III → I → V
E) III → IV → II → I → V

E

25) A key part of the humoral immune response is
A) the attack of cytotoxic T cells on infected host cells.
B) the production of antibodies by plasma cells.
C) perforation of infected host cells by perforin.
D) the attack of phagocytes on living pathogens.
E) the initiation of programmed cell death in infected host cells.

B

26) The receptors on T cells and B cells bind to
A) antibodies.
B) antigens.
C) natural killer cells.
D) double-stranded RNA.
E) immunoglobulins.

B

27) An epitope is
A) part of the interferons that penetrate foreign cells.
B) a protein protruding from the surface of B cells.
C) two structurally similar antibodies dissolved in the blood plasma.
D) that part of an antigen that actually binds to an antigen receptor.
E) a mirror image of an antigen.

D

30) Clonal selection of B cells activated by antigen exposure leads to production of
A) large numbers of neutrophils.
B) large quantities of the antigen initially recognized.
C) vast numbers of B cells with random antigen-recognition receptors.
D) long-lived erythrocytes that can later secrete antibodies for the antigen.
E) short-lived plasma cells that secrete antibodies for the antigen.

E

48) Select the pathway that would lead to the activation of cytotoxic T cells.
A) B cell contact antigen → helper T cell is activated → clonal selection occurs
B) body cell becomes infected with a virus → new viral proteins appear → class I MHC molecule-antigen complex displayed on cell surface
C) self-tolerance of immune cells → B cells contact antigen → cytokines released
D) complement is secreted → B cell contacts antigen → helper T cell activated → cytokines released
E) cytotoxic T cells → class II MHC molecule-antigen complex displayed → cytokines released → cell lysis

B

32) A newborn who is accidentally given a drug that destroys the thymus would most likely
A) lack class I MHC molecules on cell surfaces.
B) lack humoral immunity.
C) be unable to genetically rearrange antigen receptors.
D) be unable to differentiate and mature T cells.
E) have a reduced number of B cells and be unable to form antibodies.

D

35) Secondary immune responses upon a second exposure to a pathogen are due to the activation of
A) memory cells.
B) macrophages.
C) stem cells.
D) B cells.
E) T cells.

A

36) The MHC is important in a T cell's ability to
A) distinguish self from nonself.
B) recognize specific parasitic pathogens.
C) identify specific bacterial pathogens.
D) identify specific viruses.
E) recognize differences among types of cancer.

A

51) A cell type that interacts with both the humoral and cell-mediated immune pathways is a
A) plasma cell.
B) cytotoxic T cell.
C) natural killer cell.
D) CD8 cell.
E) helper T cell.

E

the nucleus and most of the organelles in a neuron are located in the

1. dendritic region
2. axon hillock
3. axon
4. cell body

D

40) The following steps refer to various stages in transmission at a chemical synapse.

1. Neurotransmitter binds with receptors associated with the postsynaptic membrane.
2. Calcium ions rush into neuron's cytoplasm.
3. An action potential depolarizes the membrane of the axon terminal.
4. The ligand-gated ion channels open.
5. The synaptic vesicles release neurotransmitter into the synaptic cleft.

Which sequence of events is correct?

A) 1 → 2 → 3 → 4 → 5
B) 2 → 3 → 5 → 4 → 1
C) 3 → 2 → 5 → 1 → 4
D) 4 → 3 → 1 → 2 → 5
E) 5 → 1 → 2 → 4 → 3

C

The point of concoction between two communicating neurons is called

1. the axon hillock
2. the dendrite
3. the synapse
4. the cell body

C

7) In a simple synapse, neurotransmitter chemicals are released by
A) the dendritic membrane.
B) the presynaptic membrane.
C) axon hillocks.
D) cell bodies.
E) ducts on the smooth endoplasmic reticulum.

B

8) In a simple synapse, neurotransmitter chemicals are received by
A) the dendritic membrane.
B) the presynaptic membrane.
C) axon hillocks.
D) cell bodies.
E) ducts on the smooth endoplasmic reticulum.

A

10) For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in
A) the depolarization of the neuron.
B) the hyperpolarization of the neuron.
C) the replacement of potassium ions with sodium ions.
D) the replacement of potassium ions with calcium ions.
E) the neuron switching on its sodium-potassium pump to restore the initial conditions.

B

12) The operation of the sodium-potassium "pump" moves
A) sodium and potassium ions into the cell.
B) sodium and potassium ions out of the cell.
C) sodium ions into the cell and potassium ions out of the cell.
D) sodium ions out of the cell and potassium ions into the cell.
E) sodium and potassium ions into the mitochondria.

D

23) Action potentials move along axons
A) more slowly in axons of large than in small diameter.
B) by the direct action of acetylcholine on the axonal membrane.
C) by activating the sodium-potassium "pump" at each point along the axonal membrane.
D) more rapidly in myelinated than in non-myelinated axons.
E) by reversing the concentration gradients for sodium and potassium ions.

D

24) A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to
A) prevent the hyperpolarization phase of the action potential.
B) prevent the depolarization phase of the action potential.
C) prevent graded potentials.
D) increase the release of neurotransmitter molecules.
E) have most of its effects on the dendritic region of a neuron.

B

63) The minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label
A) A.
B) B.
C) C.
D) D.
E) E.

A

The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label
A) A.
B) B.
C) C.
D) D.
E) E.

C

after the depolarization phase of an action potential, the resting potential is restored by

1. the opening of sodium activation gates
2. the opening of voltage-gated potassium channels and the closing of sodium channels
3. a decrease in the membranes permeability to potassium and chloride ions
4. a brief inhibition of the sodium-potassium pump

B

The "undershoot" phase of after- hyper polarization is due to

1. slow opening of voltage- gated sodium channels
2. sustained opening of voltage- gated potassium channels
3. rapid opening of voltage- gated calcium channels
4. slow restorative actions of the sodium-potassium ATPase

B

31) Saltatory conduction is a term applied to
A) conduction of impulses across electrical synapses.
B) an action potential that skips the axon hillock in moving from the dendritic region to the axon terminal.
C) rapid movement of an action potential reverberating back and forth along a neuron.
D) jumping from one neuron to an adjacent neuron.
E) jumping from one node of Ranvier to the next in a myelinated neuron.

E

33) Neurotransmitters are released from axon terminals via
A) osmosis.
B) active transport.
C) diffusion.
D) transcytosis.
E) exocytosis.

E

42) Adjacent neurons with direct (non-neurotransmitter) action potential transfer are said to have electrical synapses, based on the presence of
A) tight junctions at their point of contact.
B) gap junctions at their point of contact.
C) leaky junctions at their point of contact.
D) anchoring junctions at their point of contact.
E) desmosomes at their point of contact.

B

69) A common feature of action potentials is that they
A) cause the membrane to hyperpolarize and then depolarize.
B) can undergo temporal and spatial summation.
C) are triggered by a depolarization that reaches the threshold.
D) move at the same speed along all axons.
E) require the diffusion of Na+ and K+ through ligand-gated channels to propagate.

C

70) Where are neurotransmitter receptors located?
A) the nuclear membrane
B) the nodes of Ranvier
C) the postsynaptic membrane
D) synaptic vesicle membranes
E) the myelin sheath

C

73) Which of the following is a direct result of depolarizing the presynaptic membrane of an axon terminal?
A) Voltage-gated calcium channels in the membrane open.
B) Synaptic vesicles fuse with the membrane.
C) The postsynaptic cell produces an action potential.
D) Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft.
E) An EPSP or IPSP is generated in the postsynaptic cell.

A