BIOL 230 3

d. membrane thickness

Cholesterol serves several essential functions in mammalian cells. Which of the following is NOT influenced by cholesterol? a. membrane permeability b. membrane fluidity c. membrane rigidity d. membrane thickness

c. threshold potential

Figure 12-31 illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? a. effect of a depolarizing stimulus b. resting membrane potential c. threshold potential d. action potential

c. binding of the signal molecule to a receptor.

The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is a. phosphorylation and activation of the receptor protein. b. activation of gene expression. c. binding of the signal molecule to a receptor. d. diffusion through the plasma membrane into the cell.

c. The α subunit exchanges its bound GDP for GTP.

The following happens when a G-protein-coupled receptor activates a G protein. a. The β subunit exchanges its bound GDP for GTP. b. The GDP bound to the α subunit is phosphorylated to form bound GTP. c. The α subunit exchanges its bound GDP for GTP. d. It activates the α subunit and inactivates the βγ complex.

a. a mutation within a gene.

You discover that the underlying cause of a disease is a protein that is now less stable than the non-disease-causing version of the protein. This change is most likely to be due to a. a mutation within a gene. b. a mutation within the regulatory DNA of a gene. c. gene duplication. d. horizontal gene transfer.

b. resting membrane potential

Figure 12-32 illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? a. effect of a depolarizing stimulus b. resting membrane potential c. threshold potential d. action potential

d. action potential

Figure 12-33 illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? a. effect of a depolarizing stimulus b. resting membrane potential c. threshold potential d. action potential

a. effect of a depolarizing stimulus

Figure 12-34 illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? a. effect of a depolarizing stimulus b. resting membrane potential c. threshold potential d. action potential

b. H+

Ion channels are classified as membrane transport proteins. They discriminate between ions based on size and charge. In addition to Na+ , which one of the following ions would you expect to be able to freely diffuse through a Na+ channel? a. Mg2+ b. H+ c. K+ d. Cl−

b. SPT

It is possible to follow the movement of a single molecule or a small group of molecules. This requires the use of antibodies linked to small particles of gold, which appear as dark spots when tracked through video microscopy. What is this method called? What does the abbreviation stand for? a. SDS b. SPT c. GFP d. FRAP

d. They keep the electrochemical gradient for K+ at zero.

K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? a. They set the K+ concentration gradient to zero. b. They set the membrane potential to zero. c. They disrupt the resting membrane potential. d. They keep the electrochemical gradient for K+ at zero.

d. regulatory sequence

A mutation in the ___________ of the gene encoding the enzyme lactase enables expression of this gene in adults. a. exon b. intron c. coding sequence d. regulatory sequence

a. A mutation that arises in a mother's somatic cell often causes a disease in her daughter.

1.Which of the following statements is FALSE? a. A mutation that arises in a mother's somatic cell often causes a disease in her daughter. b. All mutations in an asexually reproducing single-celled organism are passed on to the progeny. c. In an evolutionary sense, somatic cells exist only to help propagate germ-line cells. d. A mutation is passed on to offspring only if it is present in the germ line.

b. Notch

When the cytosolic tail of the __________ receptor is cleaved, it migrates to the nucleus and affects gene regulation. a. nuclear b. Notch c. growth factor d. G-protein coupled

b. produce lipids with hydrocarbon tails that are shorter and have more double bonds

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? a. produce lipids with hydrocarbon tails that are longer and have fewer double bonds b. produce lipids with hydrocarbon tails that are shorter and have more double bonds c. decrease the amount of cholesterol in the membrane d. decrease the amount of glycolipids in the membrane

c. 2004.

A finished draft of the human genome was published in a. 1965. b. 1984. c. 2004. d. 2018.

a. The cysteine residue is covalently attached to a membrane lipid.

A group of membrane proteins can be extracted from membranes only by using detergents. All the proteins in this group have a similar amino acid sequence at their C-terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine). This sequence is essential for their attachment to the membrane. What is the most likely way in which the Cterminal sequence attaches these proteins to the membrane? a. The cysteine residue is covalently attached to a membrane lipid. b. The peptide spans the membrane as an α helix. c. The peptide spans the membrane as part of a β sheet. d. The positively charged lysine residues interact with an acidic integral membrane protein.

d. inability to import sugar into the cell

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+ → 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following is the most likely cause of the yeast cell's demise? a. toxic buildup of carbon dioxide inside the cell b. toxic buildup of ethanol inside the cell c. diffusion of ATP out of the cell d. inability to import sugar into the cell

c. is activated by two or more proteins in different signaling pathways.

A protein kinase can act as an integrating device in signaling if it a. phosphorylates more than one substrate. b. catalyzes its own phosphorylation. c. is activated by two or more proteins in different signaling pathways. d. initiates a phosphorylation cascade involving two or more protein kinases.

a. addition of a high concentration of a nonhydrolyzable analog of GTP

Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in Figure 16-13. Which of the following would enhance this effect of the acetylcholine? a. addition of a high concentration of a nonhydrolyzable analog of GTP b. addition of a drug that prevents the α subunit from exchanging GDP for GTP c. mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine d. mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein

b. Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family.

Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is FALSE? a. Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. b. Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. c. Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways. d. Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal.

a. the expression of a constitutively active phospholipase C

Activated protein kinase C (PKC) can lead to the modification of the membrane lipids in the vicinity of the active PKC. Figure 16-17 shows how G proteins can indirectly activate PKC. You have discovered the enzyme activated by PKC that mediates the lipid modification. You call the enzyme Rafty and demonstrate that activated PKC directly phosphorylates Rafty, activating it to modify the plasma membrane lipids in the vicinity of the cell where PKC is active; these lipid modifications can be detected by dyes that bind to the modified lipids. Cells lacking Rafty do not have these modifications, even when PKC is active. Which of the following conditions would lead to signal-independent modification of the membrane lipids by Rafty? a. the expression of a constitutively active phospholipase C b. a mutation in the GPCR that binds the signal more tightly c. a Ca2+ channel in the endoplasmic reticulum with an increased affinity for IP3 d. a mutation in the gene that encodes Rafty such that the enzyme can no longer be phosphorylated by PKC

b. K+ -coupled

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is NOT one of the common ways to perform active transport? a. Na+ -coupled b. K+ -coupled c. ATP-driven d. light-driven

d. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure 16-16. Which of the following statements is FALSE? a. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. b. A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. c. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available. d. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

a. yeast

Which organism has the most dense distribution of genes in their chromosomes? a. yeast b. humans c. flies d. Their genes are all equally densely distributed.

b. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure 16-16. a. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. b. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available. c. A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. d. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available.

d. In the absence of a survival signal, Bad is phosphorylated.

Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure 16-28. Which of the following statements is FALSE? a. In the presence of a survival signal, Akt is phosphorylated. b. In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. c. In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. d. In the absence of a survival signal, Bad is phosphorylated.

d. interact with signal molecules that diffuse through the plasma membrane.

All members of the nuclear receptor family a. are cell-surface receptors. b. do not undergo conformational changes. c. are found only in the cytoplasm. d. interact with signal molecules that diffuse through the plasma membrane.

b. Cl−

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion? a. HCO3 − b. Cl− c. PO4 3− d. OH−

a. affect protein folding.

An SNP found in the conserved sequence of the regulatory region of a gene is likely to a. affect protein folding. b. affect when and where the gene is expressed. c. be a new mutation. d. be found in plants as well as humans.

d. ligand-gated

An extracellular molecule binds to a channel and triggers it to move more often to the open conformation than the closed conformation, as shown in the figure. This is referred to as a ___________ channel. a. Voltage-gated b. light-gated c. mechanically gated d. ligand-gated

c. thousands

Approximately, how many distinct synapses are established on the dendrites and cell body of a motor neuron in the spinal cord? a. tens b. hundreds c. thousands d. millions

d. estrogen > propanol > alanine > sodium

Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest). alanine estrogen propanol sodium a. alanine > propanol > sodium > estrogen b. sodium > propanol > alanine > estrogen c. estrogen > propanol > sodium > alanine d. estrogen > propanol > alanine > sodium

d. by opening Cl− channels

Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? a. by closing Na+ channels b. by preventing the secretion of excitatory neurotransmitters c. by opening K+ channels d. by opening Cl− channels

c. They have long carbohydrate chains.

Both glycoproteins and proteoglycans contribute to the carbohydrate layer on the surface of the cell. Which of the following statements about glycoproteins is FALSE? a. They can be secreted into the extracellular environment. b. They have only one transmembrane domain. c. They have long carbohydrate chains. d. They are recognized by lectins.

b. preventing Ca2+ from altering the activity of molecules in the cytosol.

Ca2+ -pumps in the plasma membrane and endoplasmic reticulum are important for a. maintaining osmotic balance. b. preventing Ca2+ from altering the activity of molecules in the cytosol. c. providing enzymes in the endoplasmic reticulum with Ca2+ ions that are necessary for their catalytic activity. d. maintaining a negative membrane potential.

b. Receptor R binds to factor F to induce cell proliferation in cell line A.

Cell lines A and B both survive in tissue culture containing serum but do not proliferate. Factor F is known to stimulate proliferation in cell line A. Cell line A produces a receptor protein (R) that cell line B does not produce. To test the role of receptor R, you introduce this receptor protein into cell line B, using recombinant DNA techniques. You then test all of your various cell lines in the presence of serum for their response to factor F, with the results summarized in Table 16-9. Which of the following cannot be concluded from your results above? a. Binding of factor F to its receptor is required for proliferation of cell line A. b. Receptor R binds to factor F to induce cell proliferation in cell line A. c. Cell line A expresses a receptor for factor F. d. Factor F is not required for proliferation in cell line B.

d. Na+ -H+ exchanger

Cells make use of H+ electrochemical gradients in many ways. Which of the following proton transporters is used to regulate pH in animal cells? a. light-driven pump b. H+ ATPase c. H+ symporter d. Na+ -H+ exchanger

b. K+

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell? a. Na+ b. K+ c. Ca2+ d. Cl−

a. Na+

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell? a. Na+ b. K+ c. Ca2+ d. Cl−

c. Cl−

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following negatively charged ions is NOT primarily used to buffer positive charges inside the cell? a. PO4 3− b. OH− c. Cl− d. HCO3 −

b. the deletion of a junctional protein

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in part A of Figure 11-35. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in part B of Figure 11-35 a. a nonfunctional protein glycosylase b. the deletion of a junctional protein c. the truncation of a protein found in the extracellular matrix d. a nonfunctional flippase

a. Calcium is required to maintain the structural integrity of the junctional complex.

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in part A of Figure 11-36. When a molecule that chelates calcium is added to the cell culture medium, you observe a redistribution of that protein around the entire cell, shown in part B of Figure 11-36. Which is most likely to be true about the role of calcium in maintaining an apical distribution of protein A? a. Calcium is required to maintain the structural integrity of the junctional complex. b. Calcium is required for the binding of the junctional proteins to the cell cortex. c. Calcium is a structural component of protein A. d. Calcium inhibits the intracellular transport of protein A.

d. all of these answers are correct

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? a. varying the types of sugar monomers used b. varying the types of linkages between sugars c. varying the number of branches in the chain d. all of these answers are correct

d. contact-dependent

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling. a. endocrine b. paracrine c. neuronal d. contact-dependent

b. The βγ subunit activates the mating response but is inhibited when bound to α.

During the mating process, yeast cells respond to pheromones secreted by other yeast cells. These pheromones bind GPCRs on the surface of the responding cell and lead to the activation of G proteins inside the cell. When a wild-type yeast cell senses the pheromone, its physiology changes in preparation for mating: the cell stops growing until it finds a mating partner. If yeast cells do not undergo the appropriate response after sensing a pheromone, they are considered sterile. Yeast cells that are defective in one or more components of the G protein have characteristic phenotypes in the absence and presence of the pheromone, which are listed in Table 16-14. Which of the following models is consistent with the data from the analysis of these mutants? Explain your answer. a. The α subunit activates the mating response but is inhibited when bound to βγ. b. The βγ subunit activates the mating response but is inhibited when bound to α. c. The G protein is inactive; either the free α or free βγ complex is capable of activating the mating response. d. The G protein is active; both free α and free βγ complex are required to inhibit the mating response.

b. a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP

Figure 16-20 shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? a. a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO b. a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP c. a muscle cell that has cyclic GMP phosphodiesterase constitutively active d. a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO

c. CaM-kinase is only activated when the GPCR is active and not when the RTK is active.

Figure 16-34 shows that intracellular signaling pathways can be highly interconnected. From the information in Figure 16-34, which of the following statements is FALSE? a. The GPCR and the RTK both activate phospholipase C. b. Activation of either the GPCR or the RTK will lead to activation of transcriptional regulators. c. CaM-kinase is only activated when the GPCR is active and not when the RTK is active. d. Ras is activated only when the RTK is active and not when the GPCR is active.

c. addition of a drug that blocks protein Y from interacting with its target

Figure 16-36 shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line? a. addition of a drug that prevents protein X from activating Ras b. addition of a drug that increases the affinity of protein Y and Ras c. addition of a drug that blocks protein Y from interacting with its target d. addition of a drug that increases the activity of protein Y

d. The fetal β-globins arose from a gene duplication that occurred 200 million years ago, which gave rise to a β-globin expressed in the fetus and a β-globin expressed in the adult.

Figure 9-12 shows the evolutionary history of the globin gene family members. Given this information, which of the following statements is TRUE? a. The ancestral globin gene arose 500 million years ago. b. The α-globin gene is more closely related to the ε-globin gene than to the δ-globin gene. c. The nucleotide sequences of the two γ-globins will be most similar because they are the closest together on the chromosome. d. The fetal β-globins arose from a gene duplication that occurred 200 million years ago, which gave rise to a β-globin expressed in the fetus and a β-globin expressed in the adult.

c. The chimp DNA sequence has likely diverged at the DNA coding for amino acid 15 from the sequence found in the last common ancestor of humans and chimps.

Figure 9-17 shows the nucleotide sequence from a protein-coding region of a gene in humans, chimpanzees, and gorillas and the protein sequence produced from this gene. The seventeen amino acids encoded by this DNA are numbered below. The two codons that are not conserved in all three species have been boxed. These two codons code for amino acids 3 and 15. Which of these statements is consistent with these sequence-comparison data? a. The gorilla sequence is more similar to the chimp sequence than to the human sequence. b. Since these sequences are so similar, this protein must also be found in invertebrates. c. The chimp DNA sequence has likely diverged at the DNA coding for amino acid 15 from the sequence found in the last common ancestor of humans and chimps. d. The last common ancestor of chimps and gorillas most likely used AAA to code for amino acid number 3.

d. 100

Figure 9-7 shows an experiment used to determine the spontaneous mutation rate in E. coli. If the spontaneous mutation rate in E. coli is 1 mistake in every 109 nucleotides copied, about how many colonies would you expect to see on the plates lacking histidine if you were to assay 1011 cells from the culture for their ability to form colonies? a. 1 b. 2 c. 10 d. 100

c. interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.

Foreign substances like nicotine, morphine, and menthol exert their initial effects by a. killing cells immediately, exerting their physiological effects by causing cell death. b. diffusing through cell plasma membranes and binding to transcription factors to change gene expression. c. interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus. d. removing cell-surface receptors from the plasma membrane.

b. Water molecules form cage-like structures around hydrophobic molecules.

Formation of a lipid bilayer is energetically favorable. How does this arrangement result in higher entropy for the system, and thus make bilayer formation energetically favorable? a. Polar head groups form a hydrogen-bonding network at the interface with water. b. Water molecules form cage-like structures around hydrophobic molecules. c. Hydrogen bonds form between neighboring polar head groups in the bilayer. d. Fatty acid tails are highly saturated and flexible.

b. Chimpanzees are more closely related to gorillas than to humans.

Given the evolutionary relationship between higher primates shown in Figure 9-18, which of the following statements is FALSE? a. The last common ancestor of humans, chimpanzees, gorillas, and orangutans lived about 15 million years ago. b. Chimpanzees are more closely related to gorillas than to humans. c. Humans and chimpanzees diverged about 6 million years ago. d. Orangutans are the most divergent of the four species shown in Figure 9-18.

c. RNA polymerase

HIV is a human retrovirus that integrates into the host cell's genome and will eventually replicate, produce viral proteins, and ultimately escape from the host cell. Which of the following proteins is not encoded in the HIV genome? a. reverse transcriptase b. envelope protein c. RNA polymerase d. capsid protein

b. When membrane potential changes sufficiently, the electrical force causes voltage sensor domains to change conformation.

How are voltage-gated ion channels opened by voltage sensors? a. Voltage sensors on the channel change their amino acid side chains from positively to negatively charged. b. When membrane potential changes sufficiently, the electrical force causes voltage sensor domains to change conformation. c. Changes in membrane potential lead to increased gene expression of voltage-gated ion channel proteins. d. Ion binding to voltage sensors causes the channel pore to widen and open.

c. A change in membrane potential triggers the opening of nearby voltage-gated sodium channels in a one-way direction.

How does an action potential spread along the cell membrane? a. Potassium leak channels quickly reverse the action potential to move the membrane depolarization away from the original site. b. Voltage-gated Ca2+ channels are activated by the action potential and the calcium diffuses along the membrane. c. A change in membrane potential triggers the opening of nearby voltage-gated sodium channels in a one-way direction. d. The ions entering the cell upon triggering an action potential travel laterally along the membrane to carry the charge.

d. Voltage-gated Ca2+ channels are activated and the influx of Ca2+ triggers the release of neurotransmitters.

How is an electrical signal converted to a chemical signal at a nerve terminal? a. The influx of ions leads to a pH change, chemical transformation, and signaling. b. Mechanically gated channels change conformation due to the electrical signal and create a mechanical signal. c. Ligand-gated channels are bound by ions and open to allow the flow of neurotransmitters out of the cell. d. Voltage-gated Ca2+ channels are activated and the influx of Ca2+ triggers the release of neurotransmitters.

d. It is associated with one layer of the lipid bilayer.

How is the protein shown in the diagram associated with the plasma membrane? a. It is attached to another protein that is a transmembrane protein. b. It is linked to lipids in the bilaye in r. c. It is a membrane-spanning protein (transmembrane). d. It is associated with one layer of the lipid bilayer.

c. It becomes more positive.

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected? a. The membrane potential is not affected by Na+ . b. It becomes more negative. c. It becomes more positive. d. It is permanently reset

b. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer

If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer? a. because the hydrophilic backbone makes a hole in the membrane b. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer c. because many transmembrane alpha helices must come together in a way that neutralizes the hydrophilic backbone d. because the membrane bends in such a way that the polar heads of the lipids contact the transmembrane helix

d. Single-channel patch-clamp recordings have demonstrated that gated membrane channels will only open and close in response to specific stimuli.

In a method called patch-clamping, a glass capillary can be converted into a microelectrode that measures the electrical currents across biological membranes. Which of the following statements about the patch-clamp method is FALSE? a. The glass capillary adheres to a "patch" of membrane through the application of suction. b. The aperture in the glass capillary used to make a microelectrode is about 1 μm in diameter. c. If the experimental conditions are held constant, fluctuations in electrical currents across the patch of membrane are still observed. d. Single-channel patch-clamp recordings have demonstrated that gated membrane channels will only open and close in response to specific stimuli.

b. Most of the Alu sequences in the chimpanzee genome underwent duplication and divergence before humans and chimpanzees diverged.

In humans and in chimpanzees, 99% of the Alu retrotransposons are in corresponding positions. Which of the following statements below is the most likely explanation for this similarity? a. The Alu retrotransposon is not capable of transposition in humans. b. Most of the Alu sequences in the chimpanzee genome underwent duplication and divergence before humans and chimpanzees diverged. c. The Alu retrotransposons are in the most beneficial position in the genome for primates. d. The Alu retrotransposons must also be in the same position in flies.

b. The absorption of sunlight triggers a shift in the conformation of the protein's seven, membrane-spanning α helices, allowing a proton to leave the cell.

In the photosynthetic archaean Halobacterium halobium, a membrane transport protein called bacteriorhodopsin captures energy from sunlight and uses it to pump protons out of the cell. The resulting proton gradient serves as an energy store that can later be tapped to generate ATP. Which statement best describes how bacteriorhodopsin operates? a. The absorption of sunlight triggers a contraction of the β barrel that acts as the protein's central channel, squeezing a proton out of the cell. b. The absorption of sunlight triggers a shift in the conformation of the protein's seven, membrane-spanning α helices, allowing a proton to leave the cell. c. The absorption of sunlight triggers a restructuring of bacteriorhodopsin's otherwise unstructured core to form the channel through which a proton can exit the cell. d. The absorption of sunlight triggers the activation of an enzyme that generates ATP.

d. size of the lipid head group

Membrane curvature is influenced by the differential lipid composition of the two membrane monolayers. Which factor do you think has the largest impact on the curvature of biological membranes? a. amount of cholesterol b. charge of the lipid head group c. length of the hydrocarbon tails d. size of the lipid head group

a. moving between lipid layers

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? a. moving between lipid layers b. lateral movement c. rotation around the long axis of a fatty acid d. flexing of hydrocarbon chains

b. anchors

Membrane proteins, like membrane lipids, can move laterally by exchanging positions with other membrane components. Which type of membrane protein is expected to be the least mobile, based on their function? a. channels b. anchors c. receptors d. enzymes

a. flippases

Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks? a. flippases b. phospholipases c. convertases d. glycosylases

a. unsaturated hydrocarbons

Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference? a. unsaturated hydrocarbons b. longer hydrocarbon tails c. higher levels of sterols d. larger head groups

b. germ cells form progeny.

Mutations that occur in germ-line cells are the only ones that lead to evolutionary change because a. germ cell mutations can lead to cancer. b. germ cells form progeny. c. germ cells are the only ones that express their DNA. d. germ cells undergo meiosis.

d. Cl− (Na+ )

Negatively charged ions are required to balance the net positive charge from metal ions such as K+ , Na+ , and Ca2+ . Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses)? a. Cl− (Ca2+ ) b. PO4 3− (K+ ) c. PO4 3− (Ca2+ ) d. Cl− (Na+ )

b. cytosolic; endoplasmic reticulum

New membrane phospholipids are synthesized by enzymes bound to the __________ side of the __________ membrane. a. cytosolic; mitochondrial b. cytosolic; endoplasmic reticulum c. extracellular; plasma d. luminal; Golgi

c. cytosolic; endoplasmic reticulum

New membrane phospholipids are synthesized by enzymes bound to the __________ side of the __________ membrane. a. cytosolic; mitochondrial b. luminal; Golgi c. cytosolic; endoplasmic reticulum d. extracellular; plasma

a. hydrophobic forces.

Phospholipids assemble into in a membrane using a. hydrophobic forces. b. covalent bonds. c. assembly proteins. d. enzymes.

c. cortex.

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the a. spectrin. b. attachment complex. c. cortex. d. cytoskeleton.

a. cortex.

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the a. cortex. b. attachment complex. c. cytoskeleton. d. spectrin.

a. They are made primarily of α helices.

Porin proteins form large, barrel-like channels in the membrane. Which of the following statements about these channels is FALSE? a. They are made primarily of α helices. b. They are made primarily of β sheets. c. They cannot form narrow channels. d. They have alternating hydrophobic and hydrophilic amino acids.

a. active transport.

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called a. active transport. b. free diffusion. c. facilitated diffusion. d. passive transport.

d. spectrin

Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? a. tubulin b. attachment proteins c. actin d. spectrin

a. Chromosome 1: duplication of the gene; Chromosome 2: deletion of the gene

Shown here are regions of two homologous chromosomes. If homologous recombination occurred between the short repetitive sequence after the gene in Chromosome 1 and the short repetitive sequence before the gene in Chromosome 2, what would be the result? a. Chromosome 1: duplication of the gene; Chromosome 2: deletion of the gene b. Chromosome 1: inversion of the gene; Chromosome 2: duplication of the gene c. Chromosome 1: deletion of the gene; Chromosome 2: deletion of the gene d. Chromosome 1: duplication of the gene; Chromosome 2: duplication of the gene

d. 2

Shown is a diagram of a nerve cell. Which line indicates the location of the dendrites? a. 4 b. 3 c. 1 d. 2

c. solute concentrations on either side of the membrane

Some cells express aquaporin proteins—they are channel proteins that facilitate the flow of water molecules through the plasma membrane. What regulates the rate and direction of water diffusion across the membrane? a. aquaporin conformation b. resting membrane potential c. solute concentrations on either side of the membrane d. availability of ATP

d. glycerol and free fatty acid

Some lipases are able to cleave the covalent bonds between the glycerol backbone and the attached fatty acid. What final products do you expect to accumulate through the action of the enzyme monoacylglycerol lipase? a. phosphoglycerol and free fatty acid b. sterol and glycerol c. free phosphate and glycerol d. glycerol and free fatty acid

c. The pump is phosphorylated.

The Na+ -K+ ATPase is also known as the Na+ -K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? a. Na+ is bound b. ADP is bound c. The pump is phosphorylated. d. The pump changes conformation.

b. −52.7 mV

The Nernst equation can be used to calculate the membrane potential based on the ratio of the outer and inner ion concentration. In a resting cell, membrane potential is calculated taking only K+ ions into account. What is V when Co = 15 mM and Ci = 106 mM? a. 438.1 mV b. −52.7 mV c. 52.7 mV d. −5.3 mV

b. create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane.

The activation of the serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to a. activate the RTK. b. create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane. c. directly phosphorylate Akt. d. create DAG

c. GTP-bound form.

The active form of a monomeric GTP-binding protein is the a. guanine nucleotide exchange factor (GEF). b. GDP-bound form. c. GTP-bound form. d. GTPase-activating protein (GAP).

b. IMIVLVMLLNIGLAILFVHF

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics of α helices that form a channel are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain. a. VGHSLSIFTLVISLGIFVFF b. IMIVLVMLLNIGLAILFVHF c. ILHFFHQYMMACNYFWMLCE d. VTLHKNMFLTYILNSMIIII

a. oligosaccharide

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular __________ that is presented on the surface of a target cell. a. oligosaccharide b. aminophospholipid c. polysaccharide d. sphingolipid

a. When the transcriptional regulator is phosphorylated, it activates transcription of the ethylene-responsive genes.

The ethylene response in plants involves a dimeric transmembrane receptor. When the receptor is not bound to ethylene, the receptor binds to and activates a protein kinase, which activates an intracellular signaling pathway that leads to the degradation of a transcriptional regulator important for transcribing the ethylene-responsive genes (see Figure 16-33). You discover a phosphatase that is important for ethylene signaling, and you name it PtpE. Plants lacking PtpE never turn on ethyleneresponsive genes, even in the presence of ethylene. You find that PtpE dephosphorylates serine 121 on the transcriptional regulator. Furthermore, plants lacking PtpE degrade the transcriptional regulator in the presence of ethylene. Which of the following statements is inconsistent with your data? a. When the transcriptional regulator is phosphorylated, it activates transcription of the ethylene-responsive genes. b. When the transcriptional regulator is not phosphorylated, it binds to DNA. c. Activation of the protein kinase that binds to the ethylene receptor leads to inactivation of PtpE. d. Binding of ethylene to its receptor leads to the activation of PtpE.

c. Species N is more closely related to the last common ancestor of all of these species than to any of the other species shown in the diagram.

The evolutionary relationships between seven different species—G, H, J, K, L, M, and N—are diagrammed in Figure 9-25. Given this information, which of the following statements is FALSE? a. These are all highly related species, because the sequence divergence between the most divergent species is 3%. b. Species M is as closely related to species G as it is to species J. c. Species N is more closely related to the last common ancestor of all of these species than to any of the other species shown in the diagram. d. Species G and H are as closely related to each other as species J and K are to each other.

b. a mutation that prevents RGFR from binding to RGF

The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? a. a mutation that increases the affinity of RGFR for RGF b. a mutation that prevents RGFR from binding to RGF c. changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines d. changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid

c. a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? a. a mutation that prevents dimerization of the receptor b. a mutation that destroys the kinase activity of the receptor c. a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor d. a mutation that prevents the binding of the normal extracellular signal to the receptor

c. QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed.

The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000 -dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be TRUE? a. Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. b. Glial cells do not have a receptor for QGF. c. QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. d. Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF.

d. GTPase activity of Gα.

The length of time a G protein will signal is determined by the a. activity of phosphatases that turn off G proteins by dephosphorylating Gα. b. activity of phosphatases that turn GTP into GDP. c. degradation of the G protein after Gα separates from Gβγ. d. GTPase activity of Gα.

c. diffusing into cells and stimulating the cyclase directly.

The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by a. activating a G protein. b. activating a receptor tyrosine kinase. c. diffusing into cells and stimulating the cyclase directly. d. activating an intracellular protein kinase.

b. All changes between human individuals are single-nucleotide polymorphisms.

The nucleotide sequences between individuals differ by 0.1%, yet the human genome is made up of about 3 × 109 nucleotide pairs. Which of the following statements is FALSE? a. In most human cells, the homologous autosomes differ from each other by 0.1%. b. All changes between human individuals are single-nucleotide polymorphisms. c. Any two individuals (other than identical twins) will generally have more than 3 million genetic differences in their genomes. d. Much of the variation between human individuals was present 200,000 years ago, when the human population was small.

d. 50%

The percentage of human DNA that is in repetitive elements, including mobile genetic elements, is ___________. a. 3% b. 15% c. 1.5% d. 50%

d. Fugu has lost many genes that are part of gene families.

The pufferfish, Fugu rubripes, has a genome that is one-tenth the size of mammalian genomes. Which of the following statements is NOT a possible reason for this size difference? a. Intron sequences in Fugu are shorter than those in mammals. b. Fugu lacks the repetitive DNA found in mammals. c. The Fugu genome seems to have lost sequences faster than it has gained sequences over evolutionary time. d. Fugu has lost many genes that are part of gene families.

c. ATP hydrolysis drives the function of the pump.

The sodium-potassium pump maintains the extracellular concentration of sodium at levels that are about 20-30 times higher than inside the cells. What directly supplies the energy for maintaining this gradient? a. Sodium supplies the energy, as it is moving along its concentration gradient. b. Potassium supplies the energy, as it is moving along its concentration gradient. c. ATP hydrolysis drives the function of the pump. d. A proton gradient in the mitochondria drives the antiport.

a. acetylcholine

The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. What type of neurotransmitter is used at these neuromuscular junctions? a. acetylcholine b. glutamate c. GABA d. glycine

d. stress-gated

The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use? a. voltage-gated b. extracellular ligand-gated c. intracellular ligand-gated d. stress-gated

c. Many short stretches of DNA may lack a stop codon simply by chance, making it difficult to distinguish those DNA sequences that code for proteins from those that do not.

The yeast genome was sequenced more than 20 years ago, yet the total number of genes continues to be refined. The sequencing of closely related yeast species was important for validating the identity of short (less than 100 nucleotides long) open reading frames (ORFs) that were otherwise difficult to predict. What is the main reason that these short ORFs are Difficult to find without the genomes of other yeast for comparison? a. Short ORFs are found only in yeast. b. The short ORFs code for RNAs. c. Many short stretches of DNA may lack a stop codon simply by chance, making it difficult to distinguish those DNA sequences that code for proteins from those that do not. d. Short ORFs occur mainly in gene-rich regions, making them difficult to identify by computer programs.

c. X and Y

Three phospholipids, X, Y, and Z, are distributed in the plasma membrane as indicated in Figure 11-10. For which of these phospholipids does a flippase probably exist? a. X only b. Z only c. X and Y d. Y and Z

a. specific recognition of transport substrates.

Transporters, in contrast to channels, work by a. specific recognition of transport substrates. b. a gating mechanism. c. filtering solutes by charge. d. filtering solutes by size.

b. 50%

Two individuals are represented in Figure 9-6; individual 1 is one of the parents of individual 2. The asterisk indicates the occurrence of a single mutation. What is the chance that individual 2 will inherit the mutation in individual 1? a. 100% b. 50% c. 1 in 100,000 d. none

d. All of these answers are true.

Viral genomes a. can be made of DNA. b. can be made of RNA. c. can be either double-stranded or single-stranded. d. All of these answers are true.

c. viruses use host-cell ribosomes to produce viral coat proteins.

Viruses reproduce inside a host cell because a. viruses package DNA from the host-cell genome into the virus particle. b. viruses need host-cell reverse transcriptase to convert its RNA into DNA. c. viruses use host-cell ribosomes to produce viral coat proteins. d. all viruses must insert their genomes into the host-cell genome in order to be replicated.

a. Some channels remain closed and some open completely.

Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? a. Some channels remain closed and some open completely. b. All channels open completely. c. All channels open partly, to the same degree. d. All channels open partly, each to a different degree.

a. 2-methylpropane

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules. Which of the following molecules will cause a "cage" of water to form? a. 2-methylpropane b. acetone c. methanol d. urea

d. FRAP

We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for? a. SDS b. SPT c. GFP d. FRAP

b. H+

We know the detailed molecular structure and mechanism of action of the transmembrane protein bacteriorhodopsin. This protein uses sunlight as the source of energy to pump __________ out of the cell. a. ATP b. H+ c. K+ d. Na+

c. Viruses can leave the cell and move to other cells and organisms; mobile genetic elements generally just move around the genome within in a cell.

What is a defining difference between viruses and mobile genetic elements? a. Mobile genetic elements can insert into genomes; viruses cannot. b. Mobile genetic elements do not use RNA intermediates in their transposition process, whereas viruses use RNA intermediates for replication. c. Viruses can leave the cell and move to other cells and organisms; mobile genetic elements generally just move around the genome within in a cell. d. Viruses sometimes use cell machinery to replicate; mobile genetic elements always use their own enzymes.

c. glucose-sodium symport

What is responsible for moving glucose from the gut lumen into intestinal epithelial cells? a. uniport glucose transporter b. passive diffusion c. glucose-sodium symport d. glucose-sodium antiport

b. inactivated

What is the conformation of the voltage-gated Na+ channel that keeps the action potential from traveling backward along the axonal membrane? a. closed b. inactivated c. triggered d. open

c. There is a narrow range of mutation rates that offers an optimal balance between keeping the genome stable and generating sufficient diversity in a population.

What is the most likely explanation of why the overall mutation rates in bacteria and in humans are roughly similar? a. Cell division needs to be fast. b. Most mutations are silent. c. There is a narrow range of mutation rates that offers an optimal balance between keeping the genome stable and generating sufficient diversity in a population. d. It benefits a multicellular organism to have some variability among its cells.

b. phospholipid

What kind of lipid molecule is represented in this figure? a. Triacylglycerol b. phospholipid c. glycolipid d. cholesterol

a. more copies of the genome and RNA for translation into protein for the viral coat/envelope

What products does the transcription of an integrated retroviral DNA supply for the replicating virus? a. more copies of the genome and RNA for translation into protein for the viral coat/envelope b. RNA intermediates for direct integration into another location in the genome c. more RNA genome copies d. RNA for translation into protein for the viral coat/envelope

c. one that involves a change in gene expression

What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute? a. one that involves the release of secretory vesicles b. one that uses a phosphorylation event to activate an enzyme c. one that involves a change in gene expression d. one that involves the firing of an action potential along a neuron

a. The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras.

When Ras is activated, cells will divide. A dominant-negative form of Ras clings too tightly to GDP. You introduce a dominantnegative form of Ras into cells that also have a normal version of Ras. Which of the following statements is TRUE? a. The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras. b. The cells you create will run out of the GTP necessary to activate Ras. c. The cells you create will divide more frequently compared to normal cells in response to the extracellular signals that typically activate Ras. d. The normal Ras in the cells you create will not be able to bind GDP because the dominant-negative Ras binds to GDP too tightly.

b. hormone.

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a a. neurotransmitter. b. hormone. c. dissolved gas. d. scaffold.

c. The electrochemical potential across the membrane is zero.

When the net charge on either side of the plasma membrane is zero, what else is true? a. There is an equal number of K+ ions on each side of the plasma membrane. b. The K+ leak channels are open. c. The electrochemical potential across the membrane is zero. d. The resting membrane potential is between −20 mV and −200 mV.

b. The plasma membrane is primarily permeable to Na+ .

When using the Nernst equation to calculate membrane potential, we are making several assumptions about conditions in the cell. Which of the following is NOT a good assumption? a. The temperature is 37°C. b. The plasma membrane is primarily permeable to Na+ . c. At rest, the interior of the cell is more negatively charged than the exterior. d. K+ is the principal positive ion in the cell.

b. in the endoplasmic reticulum

Where does most new membrane synthesis take place in a eukaryotic cell? a. in the Golgi apparatus b. in the endoplasmic reticulum c. in the plasma membrane d. on ribosomes

a. a response where cAMP leads to the activation of a transcriptional regulator

Which cAMP-mediated signaling pathway would take on the order of minutes to hours for a response to develop (as opposed to seconds)? a. a response where cAMP leads to the activation of a transcriptional regulator b. a response where cAMP leads to the activation of a catabolic enzyme c. a response where cAMP leads to the activation of a biosynthetic enzyme d. a response where cAMP leads to the release of calcium ions from the ER

a. Proteins are tethered to the cell cortex.

Which mechanism best describes the process by which a budding yeast cell designates the site of new bud formation during cell division? a. Proteins are tethered to the cell cortex. b. Proteins are tethered to the cell wall. c. Proteins are tethered to the proteins on the surface of another cell. d. Protein movement is limited by the presence of a diffusion barrier

c. Proteins interact with the proteins on the surface of another cell.

Which mechanism best describes the process by which an antigen-presenting cell triggers an adaptive immune response? a. Proteins are tethered to the cell cortex. b. Proteins are tethered to the extracellular matrix. c. Proteins interact with the proteins on the surface of another cell. d. Protein movement is limited by the presence of a diffusion barrier

b. Proteins are tethered to the extracellular matrix.

Which mechanism best describes the process by which focal adhesions are formed to promote cell motility? a. Proteins are tethered to the cell cortex. b. Proteins are tethered to the extracellular matrix. c. Proteins are tethered to the proteins on the surface of another cell. d. Protein movement is limited by the presence of a diffusion barrier.

a. Proteins interact with the proteins on the surface of another cell.

Which mechanism best describes the process by which neutrophils are recruited by endothelial cells? a. Proteins interact with the proteins on the surface of another cell. b. Proteins are tethered to the cell cortex. c. Protein movement is limited by the presence of a diffusion barrier. d. Proteins are tethered to the extracellular matrix.

c. Proteins interact with the proteins on the surface of another cell.

Which mechanism best describes the process by which neutrophils are recruited by endothelial cells? a. Proteins are tethered to the cell cortex. b. Proteins are tethered to the extracellular matrix. c. Proteins interact with the proteins on the surface of another cell. d. Protein movement is limited by the presence of a diffusion barrier.

d. Protein movement is limited by the presence of a diffusion barrier

Which mechanism best describes the process by which nutrients are taken up selectively at the apical surface of the epithelial cells that line the gut and released from their basal and lateral surfaces? a. Proteins are tethered to the cell cortex. b. Proteins are tethered to the extracellular matrix. c. Proteins are tethered to the proteins on the surface of another cell. d. Protein movement is limited by the presence of a diffusion barrier

b. reverse transcriptase gene

Which of the following DNA sequences is NOT commonly carried on a DNA-only transposon? a. transposase gene b. reverse transcriptase gene c. recognition site for transposase d. antibiotic-resistance gene

b. ribosomal RNA sequence

Which of the following DNA sequences is the LEAST likely to accommodate mutations? a. DNA sequences found between genes b. ribosomal RNA sequence c. regulatory DNA sequences d. the coding sequence of a duplicated gene

b. It opens more frequently in response to a given stimulus.

Which of the following best describes the behavior of a gated channel? a. It stays open continuously when stimulated. b. It opens more frequently in response to a given stimulus. c. It opens more widely as the stimulus becomes stronger. d. It requires a stimulus to change from closed to open.

c. A mutation that changes the subcellular localization of a protein.

Which of the following changes is least likely to arise from a point mutation in a regulatory region of a gene? a. A mutation that changes the time in an organism's life during which a protein is expressed. b. A mutation that eliminates the production of a protein in a specific cell type. c. A mutation that changes the subcellular localization of a protein. d. A mutation that increases the level of protein production in a cell.

a. an aquaporin

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? a. an aquaporin b. a sodium channel c. a calcium channel d. a proton channel

a. phospholipase C > diacylglycerol

Which of the following correctly matches a G-protein-activated enzyme with the second messenger molecule it produces? a. phospholipase C > diacylglycerol b. adenylyl cyclase > inositol triphosphate c. guanylyl cyclase > GTP d. protein kinase A > Ca2+

b. A component late in the pathway inhibits an enzyme early in the pathway.

Which of the following describes negative feedback regulation? a. A component generates an all-or-none, switch-like mechanism. b. A component late in the pathway inhibits an enzyme early in the pathway. c. A component acts to further activate the signaling pathway and enhance the cell's response. d. A component amplifies the signal for a more robust response.

d. RNA splicing

Which of the following functions do you NOT expect to find in the set of genes found in all organisms on Earth? a. DNA replication b. DNA repair c. protein production d. RNA splicing

a. selective permeability

Which of the following functions of the plasma membrane is possible without membrane proteins? a. selective permeability b. intercellular communication c. import/export of molecules d. cellular movement

b. selective permeability

Which of the following functions of the plasma membrane is possible without membrane proteins? a. intercellular communication b. selective permeability c. cellular movement d. import/export of molecules

c. glycine-gated Cl− channels

Which of the following gated ion channels are involved in inhibitory synaptic signaling? a. voltage-gated Na+ channels b. voltage-gated Ca2+ channels c. glycine-gated Cl− channels d. glutamate-gated cation channels

a. All vertebrate genomes contain roughly the same number of genes.

Which of the following generalities about genomes is TRUE? a. All vertebrate genomes contain roughly the same number of genes. b. All unicellular organisms contain roughly the same number of genes. c. The larger an organism, the more genes it has. d. The more types of cell an organism has, the more genes it has.

d. reducing the temperature of the membrane

Which of the following is NOT a way that cells restrict the lateral movement of membrane proteins? a. tethering to external cell components like the extracellular matrix or adjacent cells b. anchoring to internal cell components like actin or other proteins c. establishing diffusion barriers in the membrane d. reducing the temperature of the membrane

a. The membrane reseals.

Which of the following is most likely to occur after the lipid bilayer is pierced? a. The membrane reseals. b. The membrane collapses. c. A tear is formed. d. The membrane expands.

d. voltage-gated Ca2+ channels

Which of the following is required for the secretion of neurotransmitters in response to an action potential? a. neurotransmitter receptors b. Na+ -K+ pumps c. voltage-gated K+ channels d. voltage-gated Ca2+ channels

b. Synaptic response changes in magnitude depending on frequency of stimulation.

Which of the following statements best reflects the nature of synaptic plasticity? a. New synapses are created due to the postnatal generation of neurons. b. Synaptic response changes in magnitude depending on frequency of stimulation. c. There is a change in the type of neurotransmitter used at the synapse. d. Neuronal connections are pruned during normal development.

d. A mutation that changes the TAT codon to the TAG codon in a protein-coding gene.

Which of the following is the least likely to be a selectively neutral mutation? (The codon table in Figure 9-14 will help you answer this question.) a. A mutation that deletes 50% of a pseudogene. b. A mutation that changes the CCC codon to the CCT codon in a protein-coding gene. c. A mutation that changes the TCC codon to the AGT codon in a protein-coding gene. d. A mutation that changes the TAT codon to the TAG codon in a protein-coding gene.

d. It encodes its own reverse transcriptase.

Which of the following is true of a retrovirus, but NOT of the Alu retrotransposon? a. It requires cellular enzymes to make copies. b. It can be inserted into the genome. c. It can be excised and moved to a new location in the genome. d. It encodes its own reverse transcriptase.

c. horizontal transfer

Which of the following mechanisms for genetic change involves the acquisition of genetic material from another organism? a. transposition b. gene duplication c. horizontal transfer d. mutation

a. dephosphorylation by serine/threonine phosphatases

Which of the following mechanisms is NOT directly involved in inactivating an activated RTK? a. dephosphorylation by serine/threonine phosphatases b. dephosphorylation by protein tyrosine phosphatases c. removal of the RTK from the plasma membrane by endocytosis d. digestion of the RTK in lysosomes

d. cholesterol

Which of the following membrane lipids does not contain a fatty acid tail? a. phosphatidylcholine b. a glycolipid c. phosphatidylserine d. cholesterol

b. export of Ca2+ from the cytosol

Which of the following occur WITHOUT coupling transport of the solute to the movement of a second solute? a. import of glucose into gut epithelial cells b. export of Ca2+ from the cytosol c. export of H+ from animal cells for pH regulation d. the export of Na+ from cells to maintain resting membrane potential

a. triacylglycerol

Which of the following phospholipid precursors is the most hydrophobic? a. triacylglycerol b. diacylglycerol c. phosphate d. glycerol

a. exon shuffling

Which of the following processes is NOT thought to contribute to the diversity in the genome seen between any two human individuals? a. exon shuffling b. single-nucleotide polymorphisms c. new mutations seen at birth that are not present in the genomes of either parent d. duplication and deletion of large blocks of sequence

a. the upstream regulatory region of a gene that encodes the region conferring tissue specificity

Which of the following regions of the genome is the LEAST likely to be conserved over evolutionary time? a. the upstream regulatory region of a gene that encodes the region conferring tissue specificity b. the upstream regulatory region of a gene that binds to RNA polymerase c. the portion of the genome that codes for proteins d. the portion of the genome that codes for RNAs that are not translated into protein

d. introns that contain regions of similarity to one another

Which of the following situations would facilitate the process of exon shuffling? a. shorter introns b. a haploid genome c. exons that code for more than one protein domain d. introns that contain regions of similarity to one another

d. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE? a. GPCRs are the largest family of cell-surface receptors in humans. b. GPCRs are used in endocrine, paracrine, and neuronal signaling. c. GPCRs are found in yeast, mice, and humans. d. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

d. They promote neuronal uptake of Na+ .

Which of the following statements about GABA receptors is FALSE? a. They are located on postsynaptic membranes. b. They are ligand-gated channels. c. They inhibit synaptic signaling. d. They promote neuronal uptake of Na+ .

a. Because gene duplication can occur when crossover events occur, genes are always duplicated onto homologous chromosomes.

Which of the following statements about gene families is FALSE? a. Because gene duplication can occur when crossover events occur, genes are always duplicated onto homologous chromosomes. b. Not all duplicated genes will become functional members of gene families. c. Whole-genome duplication can contribute to the formation of gene families. d. Duplicated genes can diverge in both their regulatory regions and their coding regions.

a. For protein-coding genes, homologous genes will show more similarity in their amino acid sequences than in their nucleotide sequences.

Which of the following statements about homologous genes is TRUE? a. For protein-coding genes, homologous genes will show more similarity in their amino acid sequences than in their nucleotide sequences. b. Fewer than 1% of human genes have homologs in the nematode and the fruit fly. c. Most homologous genes arose by gene duplication. d. A gene in humans that has homologs in plants and prokaryotes will show the same level of similarity in nucleotide sequence when the human and prokaryotic sequences are compared as when the human and chimpanzee sequences are compared.

a. Mobile genetic elements can sometimes rearrange the DNA sequences of the genome in which they are embedded by accidentally excising neighboring chromosomal regions and reinserting these sequences into different places within the genome.

Which of the following statements about mobile genetic elements is TRUE? a. Mobile genetic elements can sometimes rearrange the DNA sequences of the genome in which they are embedded by accidentally excising neighboring chromosomal regions and reinserting these sequences into different places within the genome. b. DNA-only transposons do not code for proteins but instead rely on transposases found in cells that are infected by viruses. c. The two major families of transposable sequences found in the human genome are DNA-only transposons that move by replicative transposition. d. During replicative transposition, the donor DNA will no longer have the mobile genetic element embedded in its sequence when transposition is complete.

a. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.

Which of the following statements about molecular switches is FALSE? a. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. b. Protein kinases transfer the terminal phosphate from ATP onto a protein. c. Serine/threonine kinases are the most common types of protein kinase. A GTP-binding protein exchanges its bound GDP for GTP to become activated

a. All pseudogenes code for microRNAs.

Which of the following statements about pseudogenes is FALSE? a. All pseudogenes code for microRNAs. b. Pseudogenes share significant nucleotide similarity with functional genes. c. Pseudogenes are no longer expressed as a protein product. d. There are approximately 11,000 pseudogenes in the human genome.

c. The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell.

Which of the following statements about resting membrane potential is FALSE? a. The resting membrane potential for most animal cells is 0 mV, because the positive and negative ions are in balance. b. The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells. c. The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell. d. At the resting membrane potential, no ions enter or exit the cell.

b. Retroviruses use the host-genome integrase enzyme to create the provirus.

Which of the following statements about retroviruses is FALSE? a. Retroviruses are packaged with a few molecules of reverse transcriptase in each virus particle. b. Retroviruses use the host-genome integrase enzyme to create the provirus. c. The production of viral RNAs can occur long after the initial infection of the host cell by the retrovirus. d. Viral RNAs are translated by host-cell ribosomes to produce the proteins required for the production of viral particles.

c. The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain.

Which of the following statements about the carbohydrate coating of the cell surface is FALSE? a. It is not usually found on the cytosolic side of the membrane. b. It can play a role in cell-cell adhesion. c. The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain. d. Specific oligosaccharides can be involved in cell-cell recognition.

d. Some of the duplicated globin genes that arose during vertebrate evolution acquired inactivating mutations and became pseudogenes in modern vertebrates.

Which of the following statements about the globin gene family is TRUE? a. The globin protein, which can carry oxygen molecules throughout an organism's body, was first seen in ancient vertebrate species about 500 million years ago. b. The gene duplication that led to the expansion of the globin gene family led to the separation and distribution of globin on many chromosomes in mammals, such that no chromosome has more than a single functional member of the globin gene family. c. As globin gene family members diverged over the course of evolution, all the DNA sequence variations that have accumulated between family members are within the regulatory DNA sequences that affect when and how strongly each globin gene is expressed. d. Some of the duplicated globin genes that arose during vertebrate evolution acquired inactivating mutations and became pseudogenes in modern vertebrates.

d. Only the exons are conserved between the genomes of humans and other mammals.

Which of the following statements about the human genome is FALSE? a. About 50% of the human genome is made up of mobile genetic elements. b. More of the human genome comprises intron sequences than exon sequences. c. About 1.5% of the human genome codes for exons. d. Only the exons are conserved between the genomes of humans and other mammals.

a. Modern humans whose ancestors come from Europe or Asia share up to 2% of their genome with Neanderthals.

Which of the following statements about what we have learned by comparing the modern-day human genome to other genomes is TRUE? a. Modern humans whose ancestors come from Europe or Asia share up to 2% of their genome with Neanderthals. b. Many of the 3 million genetic differences between the genome of two humans are the result of new mutations that have arisen within the last 2000 years. c. The human genome is far more gene-dense than the yeast genome. d. In syntenic regions of the human and mouse genomes, both gene order and the placements of more than 95% of the mobile genetic elements are conserved.

d. Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

Which of the following statements is FALSE? a. Nucleotides and amino acids can act as extracellular signal molecules. b. Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. c. Some signal molecules are transmembrane proteins. d. Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

d. Genes that code for ribosomal RNA share significant similarity in all eukaryotes but are much more difficult to recognize in archaea.

Which of the following statements is FALSE? a. The human genome is more similar to the orangutan genome than it is to the mouse genome. b. A comparison of genomes shows that 90% of the human genome shares regions of conserved synteny with the mouse genome. c. Primates, dogs, mice, and chickens all have about the same number of genes. d. Genes that code for ribosomal RNA share significant similarity in all eukaryotes but are much more difficult to recognize in archaea.

b. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

Which of the following statements is TRUE? a. Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. b. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. c. Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. d. The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.

a. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

Which of the following statements is TRUE? a. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. b. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. c. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. d. Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.

b. PI 3-kinase phosphorylates a lipid in the plasma membrane.

Which of the following statements is TRUE? a. MAP kinase is important for phosphorylating MAP kinase kinase. b. PI 3-kinase phosphorylates a lipid in the plasma membrane. c. Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. d. Dimerization of GPCRs leads to Gα activation.

a. The position of introns in most genes is conserved among vertebrates.

Which of the following statements is TRUE? a. The position of introns in most genes is conserved among vertebrates. b. The more nucleotides there are in an organism's genome, the more genes there will be in its genome. c. Because the fly Drosophila melanogaster and humans diverged from a common ancestor so long ago, any two fly genes will show more similarity to each other than it will to a human gene. d. Two closely related organisms are more likely to have a genome of the same size than a more evolutionarily diverged animal.

d. The Na+ -K+ pump helps to keep both Na+ and Cl− ions out of the cell.

Which of the following statements is TRUE? a. Amoebae have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior. b. Bacteria and animal cells rely on the Na+ -K+ pump in the plasma membrane to prevent lysis resulting from osmotic imbalances. c. The Na+ -K+ pump allows animal cells to thrive under conditions of very low ionic strength. d. The Na+ -K+ pump helps to keep both Na+ and Cl− ions out of the cell.

c. Membrane lipids diffuse within the plane of the membrane.

Which of the following statements is TRUE? a. Phospholipids will spontaneously form liposomes in nonpolar solvents. b. In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. c. Membrane lipids diffuse within the plane of the membrane. d. Membrane lipids frequently flip-flop between one monolayer and the other.

c. detergent

Which of the following substances is most commonly used to help purify a membrane protein? a. high salt solution b. sucrose c. detergent d. ethanol

c. endocrine

Which of the following types of cell signaling is long range and uses hormones as signals? a. paracrine b. contact-dependent c. endocrine d. neuronal

d. searching for long stretches of DNA sequence conservation with intron sequences from zebrafish

Which of the following would NOT be useful when finding genes in a newly sequenced mammalian genome? a. searching for splicing sequences that signal an intron-exon boundary b. searching for sequences that code for proteins similar to those found in fruit flies c. matching sequences obtained from RNA-Seq back to the genome d. searching for long stretches of DNA sequence conservation with intron sequences from zebrafish

a. a steroid hormone (nonpolar, large)

Which of the following would be able to cross a protein-free lipid bilayer most rapidly? a. a steroid hormone (nonpolar, large) b. ethanol (uncharged polar, small) c. glucose (uncharged polar, large) d. a chloride ion (charged, small)

b. 15 carbons with two double bonds

Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)? a. 24 carbons with one double bond b. 15 carbons with two double bonds c. 20 carbons with two double bonds d. 16 carbons with no double bonds

a. phospholipids

Which type of lipids are the most abundant in the plasma membrane? a. phospholipids b. glycolipids c. sterols d. triacylglycerides

d. flip-flop

Which type of movement is the least common for lipids in a bilayer? a. lateral diffusion b. rotation c. flexion d. flip-flop

c. replicative transposition

Which type of transposition mechanism leaves a copy of the transposon in its original position and copies the transposon to a new position? a. transposases b. mobilizing transposition c. replicative transposition d. cut-and-paste transposition

a. addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive

You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? a. addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive b. addition of a drug that prevents GTP hydrolysis by Gα c. addition of a drug that activates adenylyl cyclase d. addition of a drug that mimics the ligand of ERC1

c. species Y

You are interested in finding out how the budding yeast Saccharomyces cerevisiae is so good for making bread and have collected five new related species from the wild. You sequence the genomes of all of these new species and also consult with a fungal biologist to help you construct the phylogenetic tree shown in Figure 9-19. You find that species V, W, and X make pretty good bread whereas species Y and Z do not, suggesting that the last common ancestor of species X and S. cerevisiae may have the genes necessary for making good bread. You compare the gene sequences of species X and S. cerevisiae and find many identical coding sequences, but you also identify nucleotides that differ between the two species. Which species would be the best to examine to determine what the sequence was in the last common ancestor of species X and S. cerevisiae? a. species V b. species W c. species Y d. species Z

b. addition of TRK ligand and a drug that inhibits the activity of the phosphatase that acts on SZE

You are interested in further understanding the signal transduction pathway that controls the production of Pig1, a protein important for regulating cell size. Activation of the TRK receptor leads to activation of the GTP-binding protein, Ras, which then activates a protein kinase that phosphorylates the SZE transcription factor. SZE only interacts with the nuclear transport receptor when it is phosphorylated. SZE is a gene activator for the Pig1 gene. This pathway is diagrammed in Figure 16-25. Normal cells grown under standard conditions (without ligand) are 14 µm in diameter while normal cells exposed to TRK ligand are 10.5 µm in diameter. Given this situation, which of the following conditions do you predict will more likely lead to smaller cells? a. addition of TRK ligand and a drug that stimulates the GTPase activity of Ras b. addition of TRK ligand and a drug that inhibits the activity of the phosphatase that acts on SZE c. addition of TRK ligand and a drug that stimulates the degradation of Pig1 d. addition of TRK ligand and a drug that inhibits Pig1 binding to DNA

c. a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive

You are interested in how cyclic-AMP-dependent protein kinase A (PKA) functions to affect learning and memory, and you decide to study its function in the brain. It is known that, in the cells you are studying, PKA works via a signal transduction pathway like the one depicted in Figure 16-15. Furthermore, it is also known that activated PKA phosphorylates the transcriptional regulator called Nerd that then activates transcription of the gene Brainy. Which situation described below will lead to an increase in Brainy transcription? a. a mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA b. a mutation in the nuclear import sequence of PKA from PPKKKRKV to PPAAAAAV c. a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive d. a mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the α subunit of the G protein

b. Ca2+ -pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low.

You have generated antibodies that recognize the extracellular domain of the Ca2+ -pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+ ? a. Ca2+ -pumps in vesicle membranes keep cytosolic calcium levels low. b. Ca2+ -pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low. c. Ca2+ -pumps in the Golgi apparatus keep cytosolic calcium levels low. d. Ca2+ concentrations in the cytosol increase at a steady rate.

d. horizontal gene transfer.

You isolate a pathogenic strain of E. coli from a patient and discover that this E. coli strain is resistant to an antibiotic. Common laboratory strains of E. coli are not resistant to this antibiotic, nor are any other previously isolated pathogenic E. coli strains. However, such resistance has been observed in other bacteria in the hospital in which the patient was treated. This newly discovered antibiotic resistance in E. coli is most likely due to a. a mutation within a gene. b. a mutation within the regulatory DNA of a gene. c. gene duplication. d. horizontal gene transfer.

c. A mutation within an upstream enhancer of the gene.

Your friend works in a lab that is studying why a particular mutant strain of Drosophila grows an eye on its wing. Your friend discovers that this mutant strain of Drosophila is expressing a transcription factor incorrectly. In the mutant Drosophila, this transcription factor, which is normally expressed in the primordial eye tissue, is now misexpressed in the primordial wing tissue, thus turning on transcription of the set of genes required to produce an eye in the wing primordial tissue. If this hypothesis is true, which of the following types of genetic change would most likely lead to this situation? a. A mutation within the transcription factor gene that leads to a premature stop codon after the third amino acid. b. A mutation within the transcription factor gene that leads to a substitution of a positively charged amino acid for a negatively charged amino acid. c. A mutation within an upstream enhancer of the gene. d. A mutation in the TATA box of the gene.