Cell Bio Test 3 Practice Questions

(a) it occurs by the transfer of a phosphate from a substrate molecule to ADP.

Steps 7 and 10 of glycolysis are known as substrate-level phosphorylation because (a) it occurs by the transfer of a phosphate from a substrate molecule to ADP. (b) it uses molecular oxygen to produce ATP from ADP and Pi. (c) a kinase that generates ATP is phosphorylated. (d) the sugar intermediate is phosphorylated in both steps.

D. The GLUT2 transporter transports glucose with the concentration gradient so it will transport it both into and out of the cell in the direction of the gradient

The GLUT2 transporter is a passive glucose transporter found on the plasma membrane in liver cells. When blood glucose levels are high after a meal, glucose is transported by GLUT2 into liver cells for storage. When blood glucose levels are low, glucose can be transported out of the liver using the same GLUT2 transporter. How can the same transporter transport glucose in one direction in some conditions and in the opposite direction in other conditions? Choose one: A. The liver cell can flip the GLUT2 transporter so glucose is transported the opposite way when needed. B. The GLUT2 transporter imports glucose into the cell in a passive manner and uses the energy of ATP to export glucose. C. The GLUT2 transporter forms a pore across the membrane for glucose to flow through. D. The GLUT2 transporter transports glucose with the concentration gradient so it will transport it both into and out of the cell in the direction of the gradient.

D. ATP

Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy? Select an Answer A. glucose B. NADH C. water D. ATP

A .tethering proteins to the extracellular matrix B. tethering proteins to the cell cortex C. tethering proteins to the surface of another cell E. using barriers such as tight junctions

Which is a mechanism for restricting the movement of proteins in the plasma membrane? Choose one or more: A .tethering proteins to the extracellular matrix B. tethering proteins to the cell cortex C. tethering proteins to the surface of another cell D. forming a covalent linkage with membrane lipids E. using barriers such as tight junctions F. coating proteins with carbohydrates

D. electron-transport chain

Which of the following generates the largest number of ATP molecules? Select an Answer A. glycolysis B. citric acid cycle C. gluconeogenesis D. electron-transport chain

(d) a and c

Which of the following is a function of oligosaccharides attached to theglycoproteins and glycolipids of animal cell membranes? (a) to protect the cell surface against mechanical damage. (b) to maintain membrane fluidity at low temperatures. (c) mediate cell-to-cell recognition. (d) a and c

D. It has a weak affinity for electrons and a negative redox potential.

Which of the following is true of NADH? Select an Answer A. It has a strong affinity for electrons and a positive redox potential. B. It has a strong affinity for electrons and a negative redox potential. C. It has a weak affinity for electrons and a positive redox potential. D. It has a weak affinity for electrons and a negative redox potential.

(a) Actin filaments slide past the myosin filaments

Which of the following mechanisms causes the shortening of sarcomere during muscle contraction? (a) Actin filaments slide past the myosin filaments (b) Actin filaments are shortened through depolymerization (c) Movement of myosin II heads toward the minus end of actin filament (d) None of the above

D. Treat with a drug to lower the patient's cholesterol levels.

About 20% of human breast cancers have high levels of HER2 and are referred to as HER2-positive cancers. Higher HER2 levels have been found on the plasma membranes of cells with rigid plasma membranes, and lower HER2 levels on the plasma membranes of cells with less rigid plasma membranes. Which of the following treatments could potentially be added to the lapatinib treatment to further reduce cancer cell growth? Choose one: A. Treat with a drug to increase the patient's cholesterol levels. B. Treat with a drug to stabilize the interaction of cholesterol with phospholipids. C. Treat with a drug that leads to phospholipids with longer lipid tails. D. Treat with a drug to lower the patient's cholesterol levels. E. Treat with a drug that leads to increased saturated lipid tails in the phospholipids.

b. K + -coupled

Active transport requires the input of energy into a system so as to move solutes against theirelectrochemical 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

(a) because NADH provides the high energy electron for electrontransport chain.

Although ATP and NADH are both important activated carrier molecules, ATP hydrolysis provides the direct molecular energy for most biochemical reactions. Why do the mitochondria also need to generate high levels of NADH? (a) because NADH provides the high energy electron for electrontransport chain. (b) because NADH provides the high energy electrons for citric acid cycle. (c) because NADH contains more high energy electrons than ATP. (d) all of the above.

B. The kinesin would bind tightly to microtubules and not release.

An experiment was performed to determine the role that ATP plays in kinesin movement along microtubules. Kinesin and microtubules were incubated together in a test tube, but instead of ATP, a non-hydrolyzable analog of ATP was added to the tube. What impact on kinesin function do you expect to observe in the presence of this ATP analog? Choose one: A. The kinesin would walk faster along the microtubule since the kinesin would remain active while bound to ATP. B. The kinesin would bind tightly to microtubules and not release. C. The kinesin would be unable to bind to microtubules since the kinesin would remain inactive. D. The leading head would bind tightly, but the trailing head would remain free.

NADH to NAD oxidized

Anaerobically growing yeast further metabolizes the pyruvate produced by glycolysis to CO2 and ethanol as part of a series of fermentation reactions. A. What other important reaction occurs during this fermentation step?

To continue and maintain glycolysis

Anaerobically growing yeast further metabolizes the pyruvate produced by glycolysis to CO2 and ethanol as part of a series of fermentation reactions. B. Why is this reaction (NADH to NAD+) essential for the anaerobically growing cell?

A. Rubisco

As the human population grows, it becomes increasingly important to maximize crop yields. Therefore, scientists are searching for more efficient ways for plants to convert CO2 into biomass. One approach is to genetically modify plant enzymes involved in photosynthesis to increase their efficiency. Which plant enzyme, responsible for carbon fixation, is a major focus of research? Select an Answer A. Rubisco B. photosystem II C. photosystem I D. chlorophyll

15

Assume five molecules of FADH2 are made in the citric acid cycle in a given amount of time. How many NADH are made during the same time interval?

(a) calcium is required to maintain the structural integrity of tight junctions

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure below. When a molecule that binds and inhibits calcium is added to the cell culture medium, you observe the distribution of that protein around the entire cell, shown in the Figure B. 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 tight junctions (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 intracellular transport of protein A

A. competitive inhibitor of the ligand-gated ion channel on the postsynaptic cell

Curare is a chemical purified from the bark of a South American vine, Chondrodendron tomentosum. South American native hunters place the curare on arrow tips. Animals shot with these arrows die from respiratory failure. Derivatives of curare have also been developed for medical use as a muscle relaxant that causes paralysis of muscles during surgery or other procedures. In this case, the muscle cell is the postsynaptic cell. Which of the following potential drug mechanisms would fit with the main outcome of muscle paralysis? Choose one: A. competitive inhibitor of the ligand-gated ion channel on the postsynaptic cell B. agonist that leads to opening of the Ca2+ channel on the presynaptic cell C. competitive inhibitor of neurotransmitter reuptake by the presynaptic cell D. All three of these mechanisms could potentially cause muscle paralysis.

D. the opening of voltage-gated Na+ channels

During an action potential, which of the following actions does not help return the membrane to its resting potential? Choose one: A. the flow of K+ through K+ leak channels B. the opening of voltage-gated K+ channels C. the inactivation of voltage-gated Na+ channels D. the opening of voltage-gated Na+ channels

D. Endoplasmic reticulum

During differentiation, the cell rapidly expands the amount of endoplasmic reticulum and Golgi membranes needed for secreting the antibodies. Which organelle(s) will become particularly active in synthesizing new membrane lipids? Choose one or more: A. Transport vesicle B. Golgi apparatus C. Plasma membrane D. Endoplasmic reticulum

D. It alters the probability that the channel will be found in its open conformation.

For voltage-gated channels, a change in the membrane potential has what effect on the channel? Select an Answer A. It changes the width of the channel opening. B. It locks the channel in its opened or closed configuration, depending on the voltage. C. It changes which ions can pass through the channel. D. It alters the probability that the channel will be found in its open conformation.

(A) Muscle contraction will not happen

From what you know about the mechanism of muscle contraction, what would you predict to happen if you bathe the muscle fibers in a solution containing ATP and a drug that dissociates troponin from tropomyosin? (A) Muscle contraction will not happen (B) Muscle will stay contracted (C) Muscle will die (D) Muscle will increase in size

C. growing microtubules, because EB1 binds to the GTP-tubulin cap on microtubules

GTP hydrolysis and whether GTP or GDP is bound to tubulin is an important mechanism to control the dynamic instability of microtubules. Certain aspects of dynamic instability can be viewed using GFP-EB1. Which process(es) is it useful for visualizing and why? A. growing and shrinking microtubules, because EB1 binds to the GTP-tubulin cap on microtubules B. growing and shrinking microtubules, because EB1 binds to the GDP-tubulin cap on microtubules C. growing microtubules, because EB1 binds to the GTP-tubulin cap on microtubules D. shrinking microtubules, because EB1 binds to the GTP-tubulin cap on microtubules

D. They allow the stepwise oxidation of food molecules, which releases energy in small amounts.

How do enzymes maximize the energy harvested from the oxidation of food molecules? Select an Answer A. They allow a larger amount of energy to be released from food molecules such as glucose. B. They allow what would otherwise be an energetically unfavorable oxidation reaction to occur. C. They guarantee that each reaction involved in the oxidation of food molecules proceeds in just one direction. D. They allow the stepwise oxidation of food molecules, which releases energy in small amounts.

By an influx of Cl-

How do inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize?

A. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate.

How do transporters and channels select which solutes they help move across the membrane? Choose one: A. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. B. Channels allow the passage of solutes that are electrically charged; transporters facilitate the passage of molecules that are uncharged. C. Channels will allow the passage of any solute as long as it has an electrical charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. D. Both channels and transporters discriminate between solutes mainly on the basis of size and electric charge. E. Transporters discriminate between solutes mainly on the basis of size and electric charge; channels bind their solutes with great specificity in the same way an enzyme binds its substrate.

B. The sugar groups are added to the membrane glycolipids by enzymes found inside the Golgi.

How is galactosyl ceramide (a glycolipid) found in the extracellular monolayer? Choose one: A. The sugar groups are added to the membrane glycolipids by enzymes found in the cytosol and then the lipids are flipped to the extracellular monolayer. B. The sugar groups are added to the membrane glycolipids by enzymes found inside the Golgi. C. The sugar groups are added to the membrane glycolipids by enzymes found in the extracellular space. D. The sugar groups are added to the membrane glycolipids by enzymes found in the Golgi and then the lipids are flipped to the extracellular monolayer.

A. A specific flippase moves phosphatidylethanolamine to the cytoplasmic monolayer.

How is phosphatidylethanolamine found mainly in the cytoplasmic monolayer? Choose one: A. A specific flippase moves phosphatidylethanolamine to the cytoplasmic monolayer. B. A specific scramblase moves phosphatidylethanolamine to the cytoplasmic monolayer. C. Phosphatidylethanolamine is synthesized and inserted into the cytoplasmic monolayer of the plasma membrane and is thus always in the cytoplasmic monolayer. D. Phosphatidylethanolamine is synthesized and inserted into the lumen monolayer of the ER and then flipped to the cytoplasmic monolayer.

B. Microtubules would grow longer.

How would the animation of microtubule dynamics change after adding a non-hydrolysable analog of GTP to the cells expressing GFP tubulin? Choose one: A. Microtubules would shrink. B. Microtubules would grow longer. C. Microtubule dynamics would not change. D. Dynamic instability would increase as microtubules rapidly switch between growing and shrinking.

C. The microtubule depolymerizes.

If GTP hydrolysis occurs on a tubulin molecule at the plus end of a microtubule protofilament before another tubulin molecule is added, what typically happens? Choose one: A. The GDP is rapidly exchanged for a fresh molecule of GTP. B. The microtubule remains the same size. C. The microtubule depolymerizes. D. The microtubule polymerizes.

D. a free phosphate molecule

In step 6 of glycolysis, glyceraldehyde 3-phosphate, which has one phosphate group, is converted into 1,3-bisphosphoglycerate, which has two. Where does the extra phosphate group come from? Select an Answer A. ATP B. NADPH C. fructose 1,6-bisphosphate D. a free phosphate molecule

A. The hydrophobic amino acid side chains in a transmembrane helix interact with the hydrophobic interior of the bilayer.

If the backbone of a polypeptide is hydrophilic, how can a transmembrane α helix span the hydrophobic portion of the lipid bilayer? Select an Answer A. The hydrophobic amino acid side chains in a transmembrane helix interact with the hydrophobic interior of the bilayer. B. Lipids in a fluid membrane can bend inwards so their polar heads interact with the transmembrane helix. C. The hydrophilic backbone cloaks itself in a shell of water molecules. D. Transmembrane α helices only occur in sets

c) Proton gradient would be dissipated

If the inner mitochondrial membrane were rendered as permeable as the outer membrane, how would that affect oxidative phosphorylation? (a) The production of acetyl CoA would be halted (b) The production of NADH and FADH2 would be halted (c) Proton gradient would be dissipated (d) All of the above

C. more unsaturated lipid tails than membranes in Texas bacteria

Imagine you collected bacteria from the sediment in a frozen lake in Minnesota in January and compared the membranes to membranes from bacteria collected from a lake in Texas in June. Consider how the membranes would likely differ. The membranes in bacteria from the Minnesota lake would most likely have which of the following? Choose one: A. phospholipids with more negatively charged phosphate groups than membranes in Texas bacteria B. more saturated lipid tails than membranes in Texas bacteria C. more unsaturated lipid tails than membranes in Texas bacteria D. fewer lipid tails with cis double bonds than membranes in Texas bacteria

A. increase the proportion of phospholipids with unsaturated fatty acids

In a 2018 article (Budin, et al., Science vol. 362) researchers probed how membrane fluidity affects electron transport chain activity and ATP production in E. coli by manipulating membrane fluidity and measuring respiration. How could researchers have increased membrane fluidity? Choose one: A. increase the proportion of phospholipids with unsaturated fatty acids B. increase the amount of cholesterol present in the bacterial membranes C. decrease the temperature of the media the E. coli were grown in D. increase the length of the fatty acid tails in phospholipids

D. There will be more lipids than proteins.

In a patch of animal cell membrane about 10 μm2 in area, which will be true? Select an Answer A. There will be more protein molecules than lipid molecules. B. There will be about an equal number of proteins and lipids. C. Because the lipid bilayer acts as a two-dimensional fluid, there is no way to predict the relative numbers of proteins and lipids in any patch of cell membrane. D. There will be more lipids than proteins.

B. The transporter couples the passive transport of H + to active transport of lactose.

In bacteria, the transport of many nutrients, including sugars and amino acids, is driven by the electrochemical H + gradient across the plasma membrane. In E. coli, for example, an H + -lactose symport mediates the transport of the sugar lactose into the cell. Which is likely true of the H + -lactose symport? A. Lactose and H + ions bind to two different conformations of the transporter. B. The transporter couples the passive transport of H + to active transport of lactose. C. To undergo the conformational change that releases lactose into the cell, the transporter hydrolyzes ATP. D. The transporter goes through an intermediate state in which the lactose-binding site is open to both sides ofthe membrane

E. The transporter oscillates randomly between states in which it is open to either the extracellular space or the cytosol.

In bacteria, the transport of many nutrients, including sugars and amino acids, is driven by the electrochemical H+ gradient across the plasma membrane. In E. coli, for example, an H+-lactose symporter mediates the active transport of the sugar lactose into the cell. Given what you know about coupled transport, which is likely true of the H+-lactose symporter? Choose one: A. If the H+ gradient were reversed, the transporter could serve as an H+-lactose antiport. B. Lactose and H+ ions bind to two different conformations of the transporter. C. The transporter goes through an intermediate state in which the lactose-binding site is open to both sides of the membrane. D. To undergo the conformational change that releases lactose into the cell, the transporter hydrolyzes ATP. E. The transporter oscillates randomly between states in which it is open to either the extracellular space or the cytosol.

pyruvate and NADH

In cells that cannot carry out fermentation, which products derived from glycolysis will accumulate under anaerobic conditions? Choose one: pyruvate and NADH glucose 6-phosphate and NADH pyruvate and NAD+ lactate and NAD+ glucose and NADH

B. The substrates involved in metabolic reactions can be used by a number of different enzymes.

In eukaryotic cells, why must metabolism be tightly regulated? Select an Answer A. The substrates involved in metabolic reactions are chemically reactive. B. The substrates involved in metabolic reactions can be used by a number of different enzymes. C. Anabolic and catabolic pathways must compete for scarce resources. D. All metabolic reactions require energy.

D. oxygen (O2)

In mitochondria, what is the final electron acceptor in the electron-transport chain? Select an Answer A. carbon dioxide (CO2) B. water (H2O) C. NADH and FADH2 D. oxygen (O2)

(a) The ratio of ATP to ADP in the cytoplasm would fall.

In the final stage of the oxidation of food molecules, a gradient ofprotons is formed across the inner mitochondrial membrane, which isnormally impermeable to protons. If cells were exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe? (a) The ratio of ATP to ADP in the cytoplasm would fall. (b) NADH would build up. (c) Carbon dioxide production would cease. (d) The consumption of oxygen would fall.

(a) actin monomers are added to plus end and removed from minus end at the same time

In the process called actin treadmilling: (a) actin monomers are added to plus end and removed from minus end at the same time (b) actin filaments of the cell grow at the plus end (c) actin filaments undergo polymerization and depolymerization at the plus end (d) actin filaments form helix

.C. The myosin will be unable to bind to an actin filament.

Investigators incubate myosin with an ATP analog that can bind to myosin but cannot be hydrolyzed. What effect will this treatment have on the activity of myosin? Choose one: A. The myosin will initiate a power stroke but will not be able to bind to the actin filament again at a new position. B. No effect—the myosin will behave normally. C. The myosin will be unable to bind to an actin filament. D. The myosin will bind to an actin filament but will not be released; its movement along actin will be inhibited. E. The myosin will bind to an actin filament and initiate a power stroke, but will not be subsequently released.

Contribute to the resting membrane potential

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?

(d) None of the above

Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments? (a) They strengthen cells against mechanical stress. (b) Dimers associate with each other to form a tetramer. (c) They are found in the cytoplasm. (d) None of the above

(b) The blood cells will take up water, swell, and eventually burst.

Mammalian blood contains the equivalent of 0.15 M NaCl. What will happen if red blood cells are transferred to a solution that contains0.01 M NaCl? (a) NaCl will be exported from the red blood cells by facilitated diffusion. (b) The blood cells will take up water, swell, and eventually burst. (c) NaCl will passively diffuse into the red blood cells. (d) Water will leave the cells, causing them to shrink and collapse.

C. NADH produced by the citric acid cycle

Most of the energy for the synthesis of ATP comes from which molecule? Select an Answer A. NADH produced by glycolysis B. NADH produced by the conversion of pyruvate to acetyl CoA C. NADH produced by the citric acid cycle D. FADH2 produced by the citric acid cycle

C. NaCl, because Na+ is needed for glucose entry.

Most sports drinks contain both carbohydrates and salts. The carbohydrates replace glucose burned during exercise and the salts replace salts lost in sweat. The salt also helps the small intestine absorb glucose. Pick the answer that accurately describes which salt is most beneficial for glucose absorption. Choose one: A. HCl, because H+ is needed for glucose entry. B. KCl, because Cl- is needed for glucose entry. C. NaCl, because Na+ is needed for glucose entry. D. KCl, because K+ is needed for glucose entry.

B. dynein

Motor neuron degeneration occurs in several diseases and leads to loss of muscle control. One form of motor neuron degeneration was found to have defects in retrograde transport (backward transport to cell body, in blue below) that were caused by mutations in a gene that codes for a particular protein. What protein, when mutated, would inhibit backward, but not outward, transport along axon microtubules? Choose one: A. myosin B. dynein C. tubulin D. kinesin

A. Mutation such that formation of dimers is blocked. B. Alteration in the twist or coiling of the dimers, blocking formation of staggered tetramers. C. Alteration in head groups, so tetramers are unable to link end to end.

Mutation of the muscle-specific intermediate filament desmin leads to the rare disease desmin-related myopathy. This disorder starts with weakness of the lower limbs when patients are in their 20s or 30s. As symptoms worsen, weakness in respiratory and cardiac muscles occurs, which can lead to serious problems including sudden cardiac arrest. Which of the following mutations would disrupt desmin intermediate filament structure or function and could explain the symptoms of desmin-related myopathy? Choose all of the possible mutations. Choose one or more: A. Mutation such that formation of dimers is blocked. B. Alteration in the twist or coiling of the dimers, blocking formation of staggered tetramers. C. Alteration in head groups, so tetramers are unable to link end to end. D. Disruption of the polarity of the final desmin strands.

A. The Golgi apparatus fails to organize at the normal site near the nucleus. D. The cell cycle arrests in mitosis.

Nocodazole is a microtubule-specific drug that binds free tubulin dimers and blocks microtubule polymerization. Adding nocodazole to cells causes multiple effects. Which of the following would occur after nocodazole is added to cells growing in culture? Choose one or more: A. The Golgi apparatus fails to organize at the normal site near the nucleus. B. The nucleus has structural problems. C. Muscle cells show decreased muscle contraction. D. The cell cycle arrests in mitosis.

-increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid

Organisms that live in cold climates adapt to low temperatures by doing which of the following? Choose one: increasing the amounts of saturated fatty acids in their membranes to help decrease the fluidity of their membranes -increasing the amounts of saturated fatty acids in their membranes to help keep their membranes fluid -increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid -decreasing the amounts of unsaturated fatty acids in their membrane to help keep their membranes fluid -increasing the amounts of unsaturated fatty acids in their membranes to help decrease the fluidity of their membranes

E. The acetylcholine receptor Na+ channel will be open more often when pyrantel is bound.

Pyrantel is one drug used to treat roundworm infections in dogs. Pyrantel acts as an agonist (activator) of acetylcholine receptors. Activation of acetylcholine receptors causes sudden muscle contraction and paralysis of the roundworm muscles. This causes the worm to release from the dog's intestinal wall, so the worm is passed in the dog's stool. Which of the following statements about pyrantel-bound acetylcholine receptors is true? Choose one: A. The acetylcholine receptor Na+ channel will be permanently opened by pyrantel binding. B. The acetylcholine receptor Na+ channel will be open more narrowly when pyrantel is bound. C. The acetylcholine receptor Na+ channel will be open less often when pyrantel is bound. D. The acetylcholine receptor Na+ channel will be open wider when pyrantel is bound. E. The acetylcholine receptor Na+ channel will be open more often when pyrantel is bound.

A. After death, ATP production ceases and ATP is needed for myosin release from actin.

Rigor mortis is a muscle stiffening that sets in a few hours after death. It is due to muscles being in a contracted state. It dissipates after several days as muscle proteins degenerate and cells break down. Rigor mortis is one sign that coroners take into account when estimating a time of death. At a cellular level, what is the mechanism behind rigor mortis? Choose one: A. After death, ATP production ceases and ATP is needed for myosin release from actin. B. After death, calcium ions are no longer available to bind troponin. C. After death, membranes become leaky, and sodium flowing into motor neurons trigger action potentials that contract muscles. D. In the absence of ATP, kinesin and dynein no longer move along microtubules and remain locked in place.

C. Blocking selectins would block the ability of selectin to bind leukocytes, so leukocytes would be less likely to move slowly along the vessel wall and cause a blockage of red blood cells.

Sickle cells abnormally stick to each other and can become trapped by leukocytes (white blood cells) that are rolling or paused on the endothelial cells lining the vessel. This causes blockages of small blood vessels, causing severe pain and strokes called vaso-occlusive crisis. A new drug that binds and blocks selectin proteins is in phase III clinical trials to test for improvement in patients' symptoms. Why might this be an effective treatment for vaso-occlusive crisis? Choose one: A. Blocking selectins would reduce activation of pain sensors in the blood vessels. B. Blocking selectins would block the ability of selectin to bind carbohydrates on the surface of red blood cells, preventing the blockage. C. Blocking selectins would block the ability of selectin to bind leukocytes, so leukocytes would be less likely to move slowly along the vessel wall and cause a blockage of red blood cells.

A. oxygen, glucose, sodium ions

Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest? Choose one: A. oxygen, glucose, sodium ions B. glucose, sodium ions, oxygen C. oxygen, sodium ions, glucose D. sodium ions, oxygen, glucose E. glucose, oxygen, sodium ions

(c) Level of ATP and byproducts of ATP

Step 3 in glycolysis requires the activity of phosphofructokinase to convertfructose 6-phosphate into fructose 1,6-bisphosphate. What determines if this step proceed in glycolysis or gluconeogenesis? (a) Level of glucose (b) Level of pyruvate (c) Level of ATP and byproducts of ATP (d) None of the above

d. All choices are correct

The Na+ -K + ATPase is also known as the Na+ -K + pump. Which of the following is a function of this pump? a. Maintaining the high concentration of Na+ outside the cell b. Maintaining the high concentration of K+ inside the cell c. Establishment of resting membrane potential d. All choices are correct

(d) A molecule of ATP binds pump

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 Na+ binds to its binding site on the pump? (a) Pump is phosphorylated (b) Pump is dephosphorylated (c) Pump changes conformation (d) A molecule of ATP binds pump

D. voltage-gated Ca2+ channels in the plasma membrane

The depolarization of the nerve-terminal plasma membrane triggers the secretion of neurotransmitters by opening which of the following? Select an Answer A. voltage-gated Na+ channels in the plasma membrane B. voltage-gated K+ channels in the plasma membrane C. transmitter-gated Ca2+ channels in the plasma membrane D. voltage-gated Ca2+ channels in the plasma membrane

E. It inhibits the opening of acetylcholine-gated Na+ channels in the muscle cell membrane.

The drug scopolamine is used to treat dizziness, motion sickness, and smooth muscle spasms. When isolated muscle cells are incubated with scopolamine, addition of acetylcholine no longer depolarizes the muscle cell membrane or stimulates muscle cell contraction. Which would best explain how scopolamine exerts its muscle-relaxing effects? Choose one: A. It inhibits the opening of Ca2+ channels in the sarcoplasmic reticulum. B. It inhibits the transporters that pump Ca2+ into the muscle cell cytosol during an action potential. C. It inhibits the transporters that pump Na+ into the muscle cell cytosol during an action potential. D. It inhibits the opening of voltage-gated K+ channels. E. It inhibits the opening of acetylcholine-gated Na+ channels in the muscle cell membrane.

a. glucose-Na+ symport and passive glucose uniport.

The epithelial cells that line the gut epithelium pump glucose from the gut lumen across the gut epithelium and ultimately into the blood. This process involves the function of a. glucose-Na+ symport and passive glucose uniport. b. glucose-Na+ symport and active glucose uniport. c. glucose-Na+ antiport and glucose channel. d. glucose channels.

D. The cells have glucose uniports in their plasma membrane.

The epithelial cells that line the gut have glucose-Na+ symport proteins that actively take up glucose from the lumen of the gut after a meal, creating a high glucose concentration in the cytosol. How do these cells release that glucose for use by other tissues in the body? Select an Answer A. The cells run the glucose-Na+ symport proteins in reverse. B. The cells have a glucose pump that expels the glucose needed by other tissues. C. The cells have glucose channels in their plasma membrane. D. The cells have glucose uniports in their plasma membrane.

D. fermentation

The first living cells on Earth are suspected to have generated ATP by what process? Select an Answer A. photosynthesis B. aerobic cell respiration C. oxidative phosphorylation D. fermentation

A. The reaction generates the product fructose 1,6-bisphosphate. B. The enzyme uses an ATP. C. The enzyme that catalyzes step 3 is phosphofructokinase. D. The reaction is an irreversible reaction.

The main regulatory step of glycolysis occurs in step 3. Choose all of the following that correctly describe some aspect of step 3 in glycolysis. Choose one or more: A. The reaction generates the product fructose 1,6-bisphosphate. B. The enzyme uses an ATP. C. The enzyme that catalyzes step 3 is phosphofructokinase. D. The reaction is an irreversible reaction.

a. Uptake of the glucose from lumen of gut

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following could not occur if the lipid bilayer was lacking these proteins? a. Uptake of the glucose from lumen of gut b. Membrane fluidity c. Membrane flexibility d. Simple diffusion across the membrane

Acetylcholine binds to the AcH receptor, a ligand gated channel, releasing Na+ into the muscle cell which alters membrane potential and can lead to an action potential

The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. How is the chemical signal converted into an electrical signal in the postsynaptic muscle cell?

D. It must interact with polar groups in the narrowest part of the channel.

To pass through the pore of an ion channel, what must be true of an ion? Select an Answer A. It must surround itself with water molecules. B. It must avoid contact with the channel wall. C. It must be positively charged. D. It must interact with polar groups in the narrowest part of the channel.

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.

D. High ADP activates phosphofructokinase

Weight loss can occur when glucose is oxidized to CO2 rather than being stored as glycogen. The first step in glucose oxidation is glycolysis. A 1930s diet drug, DNP, made the inner mitochondrial membrane permeable to protons, increasing the rate of glycolysis. What is the explanation for the DNP-induced increase in glycolysis? Choose one: A. High ATP activates phosphofructokinase. B. High AMP inhibits phosphofructokinase. C. DNP also makes the inner mitochondrial membrane leaky to glucose, increasing the rate of glycolysis. What is the explanation for the DNP-induced increase in glycolysis? Choose one: A. High ATP activates phosphofructokinase. B. High AMP inhibits phosphofructokinase. C. DNP also makes the inner mitochondrial membrane leaky to glucose, increasing the ability of the mitochondria to perform glycolysis. D. High ADP activates phosphofructokinase.

- lubricate cells to keep them from sticking together - protect the cell from mechanical and chemical damage - establish a distinctive identity for cell-cell recognition

What function is served by the carbohydrates attached to cell-surface proteins? Choose one or more: - allow cells to establish and maintain their shape - lubricate cells to keep them from sticking together - protect the cell from mechanical and chemical damage - establish a distinctive identity for cell-cell recognition

D. They are evolutionarily ancient and likely provided energy for the earliest cells on Earth.

What is true of the evolution of electron-transport systems? Select an Answer A. They are a relatively recent evolutionary innovation. B. The earliest ones involved using H2O as an electron donor. C. In ancient prokaryotes, they did not require the use of a membrane. D. They are evolutionarily ancient and likely provided energy for the earliest cells on Earth.

A. It is approximately the membrane potential at which the electrochemical gradient for Na+ is zero.

When a neuron is activated by a stimulus, its plasma membrane will change until it reaches a membrane potential of about +40 mV. What is special about this value? Choose one: A. It is approximately the membrane potential at which the electrochemical gradient for Na+ is zero. B. It is the opposite of the resting membrane potential. C. It is the threshold potential at which voltage-gated Na+ channels close. D. It is the threshold potential that opens voltage-gated Na+ channels. E. It is approximately the membrane potential at which the electrochemical gradient for K+ is zero.

D. the concentrations of glucose on either side of the membrane

When glucose moves across a phospholipid bilayer by passive transport, which factor determines the direction of its transport? Select an Answer A. the charge difference across the membrane B. the amount of energy available to fuel the transport process C. whether the cell is metabolically active or not D. the concentrations of glucose on either side of the membrane

D. Na+ binds to its binding site.

When the glucose-Na+ symport protein is in its outward-open state, which is more likely to occur? Select an Answer A. Glucose binds to its binding site. B. The transporter releases Na+ into the cell. C. The transporter releases glucose into the cell. D. Na+ binds to its binding site.

D. The channels alter the ion permeability of the postsynaptic membrane, which in turn may depolarize the postsynaptic membrane.

When transmitter-gated ion channels in the membrane of a postsynaptic cell open in response to neurotransmitter binding, what happens? Select an Answer A. The channels always trigger an immediate and sustained action potential. B. The channels remain open until an inhibitory neurotransmitter triggers their closure. C. The channels convert an electrical signal to a chemical signal. D. The channels alter the ion permeability of the postsynaptic membrane, which in turn may depolarize the postsynapt

B. It depolarizes.

When voltage-gated Na+ channels in a nerve cell open, what happens to the axonal membrane? Choose one: A. No change in the membrane potential occurs. B. It depolarizes. C. The membrane potential rises to 0 mV and stays there. D. It becomes electrically charged. E. The nerve cell becomes more negatively charged inside than outside.

(b) Passage of solutes across the cell membrane by transport proteins

Which of the following statement is a correct definition of facilitated diffusion in eukaryotic cells? (a) Passage of solutes across the cell membrane without aid (b) Passage of solutes across the cell membrane by transport proteins (c) Diffusion of water across the cell membrane without aid (d) Transport of vesicles along the microtubules by motor proteins

(d) None of the above

Which of the following statements about ATP production in animal cell is false? (a) One molecule of fat produces more ATP than one molecule of glucose. (b) The majority of cellular ATP is produced by oxidative phosphorylation. (c) NADH and FADH2 donate their high energy electrons to ETC to build proton gradient. (d) None of the above

B. Each filament is made of eight strands, and each strand is made from staggered tetramers linked end to end. C. Intermediate filaments protect cells from mechanical stress because they have high tensile strength and resist stretching. D. Intermediate filaments can connect cells at cell-cell junctions called desmosomes.

Which of the following statements are consistent with the structure and function of intermediate filaments? Choose one or more: A. Intermediate filaments are constructed of identical subunits found in all eukaryotic cells. B. Each filament is made of eight strands, and each strand is made from staggered tetramers linked end to end. C. Intermediate filaments protect cells from mechanical stress because they have high tensile strength and resist stretching. D. Intermediate filaments can connect cells at cell-cell junctions called desmosomes.

d) The opening of transmitter-gated K+ channels helps to repolarize the membrane.

Which of the following statements does not accurately describe the events involved in the propagation of an action potential? (a) An initial influx of Na+ through voltage-gated Na+ channels causes local depolarization of the membrane. (b) Local depolarization causes nearby Na+ channels to open. (c) Channels in depolarized regions of the membrane are inactivated until the resting membrane potential is reestablished. d) The opening of transmitter-gated K+ channels helps to repolarize the membrane.

D. Na+ is the most plentiful positively charged ion outside of the cell, while K+ is the most plentiful on the inside.

Which of the following statements is true? Select an Answer A. K+ is the most plentiful positively charged ion outside the cell, while Na+ is the most plentiful inside. B. K+ and Na+ are present in the same concentration on both sides of the plasma membrane. C. K+ and Na+ are both maintained at high concentrations inside the cell compared to out. D. Na+ is the most plentiful positively charged ion outside of the cell, while K+ is the most plentiful on the inside.

c) Exporting glucose out of the gut epithelial cells

Which of the following transports is a passive transport? a) Importing glucose into the gut epithelial cells from the gut lumen b) Exporting proton out of the cell c) Exporting glucose out of the gut epithelial cells d) None of the above

A. corneal damage caused by cell rupture from mechanical trauma

Which of the following would be a consequence of mutations that disrupt the interaction between cross-linking, stabilizing proteins and keratin filaments? Choose one: A. corneal damage caused by cell rupture from mechanical trauma B. defects in muscle development caused by improper organization of sarcomeres C. developmental defects caused by abnormal assembly of cilia D. neurodegeneration caused by an interference with normal axonal transport E. skeletal and cardiac abnormalities caused by a weakened nuclear envelope

B. addition of a phosphate to the end of the lipid tail

Which of the following would be most likely to disrupt lipid bilayer formation? Choose one: A. addition of cholesterol to the membrane B. addition of a phosphate to the end of the lipid tail C. addition of a hydroxyl group to the head group of the lipid D. addition of a methyl group to the end of the lipid tail

A. addition of a leaky Ca2+ channel to the sarcoplasmic reticulum B. blockage of the Ca2+ pump

Which of the following would increase the level of muscle contraction? Choose one or more: A. addition of a leaky Ca2+ channel to the sarcoplasmic reticulum B. blockage of the Ca2+ pump C. addition of a molecule to bind free Ca2+ D. mutation in troponin such that it no longer binds tropomyosin

(b) Addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers.

Which of the situations below will enhance microtubule polymerization and growth? (a) Addition of a drug that inhibits the exchange of GDP for GTP on free tubulin dimers. (b) Addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers. (c) Addition of a drug that decrease the affinity of tubulin dimers carrying GDP for other tubulin molecules. (d) Addition of a drug that binds to free tubulin dimers in cytosol and blocks their addition to plus end of microtubule.

A. It is consumed by oxidative phosphorylation in mitochondria.

Which of these represents the fate of a portion of the O2 produced by photosynthesis in chloroplasts? Select an Answer CORRECT A. It is consumed by oxidative phosphorylation in mitochondria. B. It is converted to the CO2 used in carbon fixation in the chloroplast stroma. C. It serves as the final electron acceptor in the photosynthetic electron-transport chain. D. It donates electrons to the mitochondrial electron-transport chain.

oxidative phosphorylation

Which stage in the breakdown of a piece of toast you had for breakfast generates the most ATP?

B. Oxaloacetate is regenerated by the end of the citric acid cycle. D. NADH is generated in steps 3, 4, and 8.

Which statements below accurately describe an aspect of the citric acid cycle? Choose one or more: A. The citric acid cycle produces two kinds of high-energy molecules, GTP and NADH. B. Oxaloacetate is regenerated by the end of the citric acid cycle. C. The two carbons that enter as acetyl CoA are released in the same cycle as CO2. D. NADH is generated in steps 3, 4, and 8.

D. transporters

Which type of membrane transport protein can perform both active and passive transport? Select an Answer A. channels B. both channels and transporters C. Neither type of membrane transport protein can perform both passive and active transport. D. transporters

- to allow membranes, under appropriate conditions, to fuse with one another and mix their molecules - to permit membrane lipids and proteins to diffuse from their site of synthesis to other regions of the cell - to ensure that membrane molecules are distributed evenly between daughter cells when a cell divides

Why must all living cells carefully regulate the fluidity of their membranes? Choose one or more: -to allow membranes, under appropriate conditions, to fuse with one another and mix their molecules -to permit membrane lipids and proteins to diffuse from their site of synthesis to other regions of the cell -to constrain and confine the movement of proteins within the membrane bilayer -to ensure that membrane molecules are distributed evenly between daughter cells when a cell divides -to allow cells to function at a broad range of temperatures

Energy would be lost as heat

Why would it not be advantageous for living systems to evolve a mechanism for the direct transfer of electrons from NADH to O2?

fat

You are packing for a hiking trip during which you'll be burning a lot of calories with physical activity. You want to pack as efficiently as possible since you need to carry a tent and all your food. You can get the most calories out of 5kg of food if it is in the form of...

A. The pump ran out of Na+ to pump because it pumps 3 Na+ out for every 2 K+ pumped in.

Your friend now has the pumps successfully pumping ions. She added an equal concentration of both ions to the correct sides of the liposomes along with an excess of the energy source. She is surprised when the pumps stop working after a short time. Which of the following could explain why the transporter stopped pumping ions? Choose one: A. The pump ran out of Na+ to pump because it pumps 3 Na+ out for every 2 K+ pumped in. B. The pump ran out of both Na+ and K+ because an equal number of both ions is pumped in each cycle. C. The pump ran out of K+ to pump because it pumps 3 K+ out for every 2 Na+ pumped in. D. The liposomes ran out of pumps to pump ions.

(a) They will accumulate fats because cells can convert glycolytic metabolites into lipids.

Your friends are on a low-fat, high-carbohydrate diet, which they claim will prevent fat accumulation within their bodies. They eat tons of pasta and bread without worrying about calorie count. What can you correctly say to your friends about their potential to accumulate lipids on their low-fat diet? (a) They will accumulate fats because cells can convert glycolytic metabolites into lipids. (b) They will not accumulate fats because cells have no way of storing fats. (c) They will not accumulate fats because carbohydrates have less energy per gram than fats. (d) They will accumulate fats because cells have no way of storing carbohydrates.