Which of the following statements is true regarding the molecule illustrated in Figure 5.2?
A) It is a saturated fatty acid.

B) It is a saturated fatty acid and a diet rich in this molecule may contribute to atherosclerosis.

C) A diet rich in this molecule may contribute to atherosclerosis.
D) Molecules of this type are usually liquid at room temperature.

E) It is a saturated fatty acid, a diet rich in this molecule may contribute to atherosclerosis, and molecules of this type are usually liquid at room temperature.

B

Which of the following statements is true regarding the molecule illustrated in Figure 5.3?
A) It is a saturated fatty acid.

B) Molecules of this type are usually liquid at room temperature.

C) A diet rich in this molecule may contribute to atherosclerosis.

D) It is a saturated fatty acid and a diet rich in this molecule may contribute to atherosclerosis.
E) It is a saturated fatty acid, a diet rich in this molecule may contribute to atherosclerosis, and molecules of this type are usually liquid at room temperature.

B

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 statements is/are true regarding the chemical reaction illustrated in Figure 5.5?

A) It results in a peptide bond.
B) It is a hydrolysis reaction.
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.

A

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

A) is more closely related to frogs than to humans.
B) is more closely related to humans than to frogs.
C) evolved at about the same time as frogs, which is much earlier than primates and mammals.
D) is more closely related to humans than to rats.
E) is more closely related to frogs than to humans and also evolved at about the same time as frogs, which is much earlier than primates and mammals.

A

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) exist in either linear chain or ring forms.
C) differ in the location of their double bonds.

D) are mirror images of one another.

E) differ in the arrangement of atoms around their double bonds.

D

A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?

A) It should dissolve in water.
B) It lacks an asymmetric carbon, and it is probably a fat or lipid.
C) It should dissolve in a nonpolar solvent.
D) It won't form hydrogen bonds with water.
E) It is hydrophobic.

A

Which two functional groups are always found in amino acids?
A) ketone and methyl

B) carboxyl and amino
C) carbonyl and amino
D) amino and sulfhydryl
E) hydroxyl and carboxyl

B

Which of the following is not a monomer/polymer pairing?
A) monosaccharide/polysaccharide

B) amino acid/protein

C) deoxyribonucleotide/DNA

D) ribonucleotide/RNA

E) triglyceride/phospholipid bilayer

E

What is the chemical reaction mechanism by which cells make polymers from monomers?
A) phosphodiester linkages

B) hydrolysis

C) ionic bonding of monomers

D) the formation of disulfide bridges between monomers

E) dehydration reactions

E

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) C₁₈H₃₂O₁₆

B) C₁₈H₃₆O₁₈

C) C₆H₁₀O₅

D) C1₈H₁₀O₁₅

E) C₃H₆O₃

A

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

B) They are hydrophilic.

C) They exhibit considerable molecular complexity and diversity.

D) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

E) They are lighter than water.

D

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 structural and optical isomers

D) different asymmetric carbons

E) different side chains (R groups) attached to an α carbon

E

The tertiary structure of a protein is the
A) bonding together of several polypeptide chains by weak bonds.

B) unique three-dimensional shape of the fully folded polypeptide.

C) order in which amino acids are joined in a polypeptide chain.

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.

B

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

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

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

C) cause the tertiary structure of the protein to unfold.

D) always alter the biological activity or function of the protein.

E) always alter the primary structure of the protein and disrupt its biological activity.

A

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 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) constructing an extensive cell wall or extracellular matrix.

C) producing primarily cytoplasmic proteins.

D) digesting large food particles.

E) enlarging its vacuole.

C

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) mitochondrion

D)the lysosome

E)membrane-bound ribosomes

D

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

A) vacuole

B)Golgi apparatus

C)mitochondrion

D)lysosome

E)peroxisome

B

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

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) any multicellular organism, like a plant or an animal.

D) nearly any eukaryotic organism.

E) any kind of organism.

C

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) secondary

B) primary

C) tertiary

D) quaternary

E) primary, secondary, tertiary, and quaternary

A

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

A) Its structure is not derived from the ER or Golgi.

B) It is a static structure.

C) It has too many vesicles.

D) It is not involved in protein synthesis.

E) It is not attached to the outer nuclear envelope.

A

What types of proteins are not synthesized in the rough ER?
A) endoplasmic reticulum proteins

B) extracellular matrix proteins

C) mitochondrial proteins

D) secreted proteins

E) plasma membrane proteins

C

Which animal cell organelle contains enzymes that transfer hydrogen from various substrates to oxygen?

A) peroxisome

B) lysosome

C) vacuole

D) mitochondrion

E) Golgi apparatus

A

The evolution of eukaryotic cells most likely involved

A) anaerobic archaea taking up residence inside a larger bacterial host cell to escape toxic oxygen-the anaerobic bacterium evolved into chloroplasts.

B) endosymbiosis of an aerobic bacterium in a larger host cell-the endosymbiont evolved into mitochondria.

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.

B

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

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

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

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

Five dialysis bags, constructed from a semipermeable membrane that is impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed.

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
A) A
B) B
C) C
D) D
E) E

C

Which line in the graph represents the bag with the highest initial concentration of sucrose?
A) A
B) B
C) C
D) D
E) E

A

Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?
A) A and B
B) B
C) C
D) D
E) D and E

B

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

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.

71) The CFTR protein belongs to what category of membrane proteins?
A) gap junctions
B) aquaporins
C) electrogenic ion pumps
D) cotransporters
E) hydrophilic channels

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

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

E

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 cotransport of glucose and hydrogen
B. by using active transport
C. by increasing the percentage of cholesterol molecules in the membrane
D. by increasing the percentage of unsaturated phospholipids in the membrane
E. by decreasing the number of hydrophobic proteins in the membrane

D

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

A. exposed on only one surface of the membrane.
B. amphipathic, with at least one hydrophobic region.
C. completely covered with phospholipids.
D. hydrophobic.
E. hydrophilic.

B

The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

A. to maintain the integrity of a fluid mosaic membrane.
B. to mediate cell-to-cell recognition.
C. to maintain membrane fluidity at low temperatures.
D. to facilitate diffusion of molecules down their concentration gradients.
E. to actively transport molecules against their concentration gradients.

B

Why are lipids and proteins free to move laterally in membranes?

A. Molecules such as cellulose can pull them in various directions.
B. The interior of the membrane is filled with liquid water.
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. Lipids and proteins repulse each other in the membrane.

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. Membrane proteins are made of only acidic amino acids.
B. The membrane is only fluid across a very narrow temperature range.
C. Proteins rarely move in the membrane.
D. The concentration of protein molecules appears to be much higher.
E. Unsaturated lipids are excluded from the membranes and do not contribute to membrane fluidity.

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 chemical constitution of the inner and outer layer of the cell membrane is predetermined by genes.
D. The two sides of a cell membrane face different environments and carry out different functions.
E. Proteins only function on the cytoplasmic side of the cell membrane, which results in the membranes asymmetrical nature.

D

Which of the following is true for the evolution of cell membranes?

A. An individual organism selects its preferred type of cell membrane for particular functions.
B. The evolution of cell membranes is driven by the evolution of glycoproteins and glycolipids.
C. The fluid mosaic nature of cell membranes provides the explanation for the evolution of cell membranes.
D. Membrane proteins are the sole component responsible for the evolution of cell membranes.
E. All components of membranes evolve as a result of natural selection.

E

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

A. active transport.
B. diffusion across the lipid bilayer.
C. cotransport.
D. facilitated diffusion.
E. osmosis.

B

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 ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
B. Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
C. A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
D. The cotransporter can also transport potassium ions.
E. Sodium and glucose compete for the same binding site in the cotransporter.

C

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. osmosis.
C. facilitated diffusion.
D. active transport.
E. cotransport.

E

What is the voltage across a membrane called?

A. chemical gradient
B. osmotic potential
C. membrane potential
D electrochemical gradient
E water potential

C

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

A. ionizes sodium and potassium atoms.
B. contributes to the membrane potential.
C. is used to drive the transport of other molecules against a concentration gradient.
D. pumps equal quantities of Na+ and K+ across the membrane.
E. pumps hydrogen ions out of the cell.

B

Ions diffuse across membranes through specific ion channels

A. down the electrical gradients.
B. down their electrochemical gradients.
C. down their chemical gradients.
D. down their concentration gradients.
E. down the osmotic potential gradients.

B

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

A. both a proton pump and a potassium channel
B. a potassium channel
C. a proton pump
D. a chloride channel
E. a sucrose-proton cotransporter

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. Cells of each domain evolved proton pumps independently when oceans became more acidic.
D. The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
E. Proton pumps are necessary to all cell membranes.

B

When protein membrane receptors are activated, what usually happens?

A. The receptors open and close in response to protein signals.
B. A change occurs on only one membrane surface: exterior or interior.
C. A change occurs in intracellular ion concentration.
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 molecules are free to move in and out of most organelles.
C. The unbound steroid receptors are quickly recycled by lysosomes.
D. The receptor may be inside the nuclear membrane.
E. The concentration of steroid receptors must be relatively high in most cells.

D

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

A. They might not be able to multiply in response to growth factors from nearby cells.
B. Hormones would not be able to interact with target cells.
C. They might compensate by receiving nutrients via a factor.
D. They could divide but never reach full size.
E. They could develop normally in response to neurotransmitters instead.

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?

A. autocrine signaling
B. hormonal signaling
C. synaptic signaling
D. endocrine signaling
E. paracrine signaling

E

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

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 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

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

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 epinephrine signals
A) a decrease in levels of cAMP as a result of bypassing the plasma membrane.
B) lower blood glucose by binding to liver cells.
C) interactions with insulin inside muscle cells.
D) interactions directly with glycogen phosphorylase.
E) elevation of cytosolic concentrations of cyclic AMP.

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