BI218 Final Exam Ch. 11-14
True or False The glucose-Na+ symport protein uses the electrochemical Na+ gradient to drive the active transport of glucose into the cell. Once this transporter has bound both Na+ and glucose, it preferentially opens toward the cytosol, where it releases both solutes.
False
True or False An electrical signal can jump across the synaptic cleft between the presynaptic and postsynaptic cells.
False
True or False An ion channel undergoes conformational changes with each ion it passes.
False
True or False Human red blood cells contain no internal membranes other than the nuclear membrane.
False
True or False Optogenetics uses transmitter-gated channels that have been introduced by genetic engineering techniques to control neurons.
False
True or False Voltage-gated ion channels are present only in electrically excitable cells, such as neurons and muscle cells.
False
True or False Water passes through the cell membrane only through specialized channels called aquaporins.
False
Intermediates formed in glycolysis and the citric acid cycle are used by the cell to synthesize: (A) amino acids. (B) lipids. (C) nucleotides. (D) All of the above (E) A and B, but not C
(D) All of the above
When the difference in redox potential between two molecules is highly positive, the transfer of electrons between them is: highly favorable. highly improbable. highly inefficient. highly unfavorable. prohibited by the laws of thermodynamics.
highly favorable.
The oils found in plant seeds and the fats found in an animal's fat (or adipose) cells are...
hydrophobic
The tails of phospholipids are...
hydrophobic
Porin proteins—which form large, water-filled pores in mitochondrial and bacterial outer membranes—fold into β-barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?
hyrophobic
In eukaryotic cells, the conversion of CO2 and H2O to sugar takes place: along the plasma membrane. in the chloroplast stroma. in the cytosol. in the mitochondrial matrix. in the thylakoid.
in the chloroplast stroma.
Organisms that live in cold climates adapt to low temperatures by...
increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid.
The enzyme glycogen phosphorylase, which breaks down glycogen, is: activated by glucose 6-phosphate and by ATP. activated by glucose 6-phosphate and inhibited by ATP. activated by glycogen and by ATP. inhibited by glucose 6-phosphate and activated by ATP. inhibited by glucose 6-phosphate and by ATP.
inhibited by glucose 6-phosphate and by ATP.
In step 6 of glycolysis, glyceraldehyde 3-phosphate, which has one phosphate group, is converted into 1,3-bisphosphoglycerate, which has two. The extra phosphate group comes from: ADP. ATP. fructose 1,6-bisphosphate. inorganic phosphate. NADPH.
inorganic phosphate.
To pass through the pore of an ion channel, an ion must...
interact with polar groups in the narrowest part of the channel
The energy efficiency of cell respiration: is about the same as that of a gasoline-powered engine. cannot be compared to that of a gasoline-powered engine. is less than that of a gasoline-powered engine. is more than that of a gasoline-powered engine.
is more than that of a gasoline-powered engine.
In passive transport, the net movement of a charged solute across the membrane is determined by...
its electrochemical gradient
A functionally specialized region of a cell membrane, typically characterized by the presence of specific proteins, is called a...
membrane domain
The voltage difference across a membrane of a cell is called the...
membrane potential
True or False When a muscle cell is stimulated, Ca2+ pumps in the sarcoplasmic reticulum use the energy of ATP to move Ca2+ into the cytosol, stimulating the cell to contract.
False
When ATP and fuel molecules such as fatty acids are abundant, the enzymes involved in glycolysis operate in the reverse direction, using pyruvate to produce glucose. False True
False
After a normal overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule? Fatty acids Glucose Glycogen Pyruvate
Fatty acids
Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis? Fermentation Gluconeogenesis The breakdown of fats The citric acid cycle The formation of acetyl CoA
Fermentation
How many oxidation reactions occur during the citric acid cycle? One: to oxidize the acetyl group that enters the cycle. Two: one for each molecule of CO2 released. Three: one for each molecule of NADH produced. Four: one for each dehydrogenase that participates in the cycle. Eight: they are all oxidation reactions, which is why cell respiration consumes so much oxygen.
Four: one for each dehydrogenase that participates in the cycle.
Which of these glycolytic reactions is catalyzed by a kinase? 3-Phosphoglycerate → 2-phosphoglycerate Dihydroxyacetone phosphate → glyceraldehyde 3-phosphate Fructose 6-phosphate → fructose 1,6-bisphosphate Glucose 6-phosphate → fructose 6-phosphate Glyceraldehyde 3-phosphate → 1,3-bisphosphoglycerate
Fructose 6-phosphate → fructose 1,6-bisphosphate
Which of the following is NOT a function of plasma membrane proteins?
Generate the energy required for lipids to diffuse through the membrane
Which of these processes does NOT involve a membrane? Generation of ATP by glycolysis Generation of ATP by oxidative phosphorylation Generation of ATP by photosynthesis in bacteria Generation of ATP by photosynthesis in plants
Generation of ATP by glycolysis
When ATP is abundant, which is likely to occur? Gluconeogenesis and glycogen breakdown Gluconeogenesis and glycogen synthesis Gluconeogenesis and mobilization of fats Glycolysis and glycogen breakdown Glycolysis and glycogen synthesis
Gluconeogenesis and glycogen synthesis
Which of the following is not a direct source of fuel for mitochondria? Acetyl CoA Amino acids Fatty acids Glucose Pyruvate
Glucose
For many anaerobic microorganisms, which metabolic pathway is the principle source of ATP? Amino acid breakdown Gluconeogenesis Glycolysis The Calvin cycle The citric acid cycle
Glycolysis
In fungi, plants, and bacteria, which pump helps to drive the import of solutes?
H+ pumps
In the electron-transport chain, what provides the main reservoir for protons that are pumped across the membrane? ATP Glucose H2O NADH O2
H2O
In the electron-transport chain, the oxygen atoms in O2 become part of which of the following molecules? ATP molecules CO2 molecules Glucose molecules (C6H12O6) H2O molecules NADH molecules
H2O molecules
In one experiment, investigators create a liposome—a vesicle made of phospholipids—that contains a solution of 1 mM glucose and 1 mM sodium chloride. If this vesicle were placed in a beaker of distilled water, what would happen the fastest?
H2O would diffuse in.
For voltage-gated channels, a change in the membrane potential has what effect on the channel?
It alters the probability that the channel will be found in its open conformation.
When Na+ channels are opened in an animal cell, what happens to the membrane potential?
It becomes less negative inside the cell
When an individual ion channel is stimulated to open (for example, by the binding of a neurotransmitter), what is the typical activity of the ion channel?
It continues to flicker between open and closed states, but spends more time open while the neurotransmitter is bound.
What is NOT true about a nerve impulse?
It depends entirely on the action of ligand-gated ion channels.
When voltage-gated Na+ channels in a nerve cell open, what happens to the axonal membrane?
It depolarizes
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?
It inhibits the opening of acetylcholine-gated Na+ channels in the muscle cell membrane.
Which is NOT true about the acetylcholine receptor on vertebrate muscle cells?
It is a voltage-gated cation channel.
When a neuron is activated by a stimulus, the membrane potential of its plasma membrane will change until it reaches about +40 mV. What is special about this value?
It is approximately the membrane potential at which the electrochemical gradient for Na+ is zero.
Which of the following accurately describes the role of the Na+ pump? It equilibrates the concentrations of Na+ and K+ across the plasma membrane. It maintains a higher K+ concentration outside the cell. It maintains a higher Na+ concentration outside the cell. It maintains a lower Na+ concentration outside the cell.
It maintains a higher Na+ concentration outside the cell.
Which is NOT true of the carbon-fixation (Calvin) cycle? It produces energy-rich ribulose 1,5-bisphosphate. It requires ATP. It requires CO2. It requires high-energy electrons from NADPH. It requires oxygen.
It requires oxygen.
In most animal cells, which ion can move through "leak" channels?
K+
Which does not occur as an action potential moves along a nerve cell membrane?
K+ flows into the cell through K+ leak channels.
Which membrane transport proteins randomly flicker between open and closed states regardless of the conditions inside or outside of the cell?
K+ leak channels
In humans and other mammals, gluconeogenesis is most likely to occur in which type of cells? Liver cells Muscle cells Nerve cells Pancreatic cells Red blood cells
Liver cells
Auditory hair cells in the ear depend on what type of ion channel to detect sound vibrations?
Mechanically-gated
In mitochondria, what is the final electron acceptor in the electron-transport chain? ADP Carbon dioxide (CO2) Molecular oxygen (O2) NADH and FADH2 Water (H2O)
Molecular oxygen (O2)
What type of enzyme catalyzes the shifting of a chemical group from one position in a molecule to another? Dehydrogenase Flippase Isomerase Kinase Mutase
Mutase
Although the citric acid cycle itself does not use O2, it requires a functioning electron-transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle? ADP ATP FADH2 NAD+ NADH
NAD+
The electron-transport chain in mitochondria accepts high-energy electrons directly from: acetyl CoA. ATP. NADH and FADH2. pyruvate. water.
NADH and FADH2.
Iron-sulfur clusters tend to have a relatively low affinity for electrons. Which component of the electron-transport chain most likely contains an iron-sulfur cluster? Cytochrome c Cytochrome c oxidase complex Cytochrome c reductase complex NADH dehydrogenase complex Ubiquinone
NADH dehydrogenase complex
Which of the following is true? NADH has a strong affinity for electrons and a negative redox potential. NADH has a strong affinity for electrons and a positive redox potential. NADH has a weak affinity for electrons and a negative redox potential. NADH has a weak affinity for electrons and a positive redox potential.
NADH has a weak affinity for electrons and a negative redox potential.
In the electron-transport chain in chloroplasts, which molecule serves as the final electron acceptor? ADP H2O NAD+ NADP+ O2
NADP+
Which of the following ions has a larger electrochemical gradient across a cell's plasma membrane? K+ Na+
Na+
Lipid bilayers are highly impermeable to...
Na+ and Cl−
When the glucose-Na+ symport protein is in its outward-open state, which is more likely to occur?
Na+ binds to its binding site
Which of the following statements is true? K+ and Na+ are both excluded from cells. K+ and Na+ are both maintained at high concentrations inside the cell. K+ and Na+ are present in the same concentration on both sides of the plasma membrane. K+ is the most plentiful positively charged ion outside the cell, while Na+ is the most plentiful inside. Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
The Na+ pump in the plasma membrane of animal cells uses energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane?
Na+ out and K+ in
Which of the following would be deterred from entering an ion channel with a negatively charged lining? Negatively charged ions Positively charged ions
Negatively charged ions
Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle, and (2) a light-activated proton pump purified from the prokaryote Halobacterium halobium. The proteins are oriented as shown in the diagram. When ADP and Pi are added to the external medium and the vesicle is exposed to light, would this system produce ATP? No, because ATP synthase is not oriented correctly. No, because cows and prokaryotes are so distantly related, so their proteins cannot be expected to work together. No, because no electron-transport chain is present. No, because protons are small enough to pass freely through an artificial lipid vesicle. Yes, the proton pump will generate a proton gradient that ATP synthase can use to synthesize ATP.
No, because ATP synthase is not oriented correctly.
Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle, and (2) a light-sensitive proton pump purified from the prokaryote Halobacterium halobium. The proteins are oriented as shown in the diagram. To this preparation, the investigators add a drug called 2,4-dinitrophenol (DNP), which makes the vesicle membrane permeable to H+. When ADP and Pi are added to the medium, and the DNP-treated vesicles are exposed to light, will ATP be produced? No. The DNP will collapse the H+ gradient that ATP synthase uses to generate ATP. Yes, because ATP synthase can operate in reverse, thus maintaining the H+ gradient. Yes, because ATP synthase is oriented in such a way that it can use the protons that leave the vesicle through DNP. Yes, because DNP cannot prevent light from activating the proton pump. Yes, because H+ can enter the vesicle through DNP.
No. The DNP will collapse the H+ gradient that ATP synthase uses to generate ATP.
In eukaryotic cells, what is the final electron acceptor in the electron-transport chain? CO2 FADH2 H2O NADH O2
O2
Which of the following is NOT required for glycolysis to occur? ADP ATP NAD+ O2 Pi
O2
When a neuron has been stimulated by a signal, the change in membrane potential first spreads locally to adjoining regions of the plasma membrane by what means?
Passive spread
The movement of an ion down its concentration gradient is called...
Passive transport
Which of the following locations is NOT used for the digestion of polymeric food molecules into monomeric subunits? Extracellular space Lysosomes The cell cytosol
The cell cytosol
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?
The cells have glucose uniports in their plasma membrane.
When glucose moves across a phospholipid bilayer by passive transport, which factor determines the direction of its transport?
The concentrations of glucose on either side of the membrane
Which of the following generates the largest amount of ATP? Fermentation Gluconeogenesis Glycolysis The citric acid cycle The electron-transport chain
The electron-transport chain
Which organelle is important for controlling the concentration of calcium ions in the cytosol?
The endoplasmic reticulum
The depolarization of the nerve-terminal plasma membrane triggers the secretion of neurotransmitters by...
opening voltage-gated Ca2+ channels in the plasma membrane.
Stage 1 of photosynthesis is in large part equivalent to: mitosis. glycolysis. oxidative phosphorylation. the carbon-fixation cycle. the citric acid cycle.
oxidative phosphorylation.
During the citric acid cycle, the acetyl group in acetyl CoA is: eliminated to produce CO2. hydrolyzed to produce CO2. oxidized to produce CO2. reduced to produce CO2. vaporized to produce CO2
oxidized to produce CO2.
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?
oxygen, glucose, sodium ions
Which is the most abundant phospholipid in animal cell membranes?
phosphatidylcholine
When protons move down their electrochemical gradient into the mitochondrial matrix, they: consume ATP. produce ATP. produce NADH. produce NAD+. move electrons through the respiratory chain.
produce ATP
When grown at higher temperatures, bacteria and yeast maintain an optimal membrane fluidity by...
producing membrane lipids with tails that are longer and contain fewer double bonds
In the electron-transport chain, as electrons move along a series of carriers, they release energy that is used to: hydrolyze ATP. oxidize food molecules. phosphorylate ADP to form ATP. pump protons across a membrane. split water into protons and oxygen.
pump protons across a membrane.
The movement of electrons through the electron-transport chain in mitochondria: consumes ATP. produces NADH. produces oxygen. pumps ATP across the inner mitochondrial membrane. pumps protons out of the matrix.
pumps protons out of the matrix.
The end products of glycolysis are: acetyl CoA, ATP, and NADH. H2O and CO2. pyruvate, ADP, and NADH. pyruvate, ATP, and NADH. pyruvate, ATP, and NADPH.
pyruvate, ATP, and NADH.
When O2 accepts electrons in the electron-transport chain, O2 becomes: oxidized. reduced.
reduced.
What do carbohydrates attached to cell-surface proteins and lipids provide for a cell? (A) A distinctive identity in cell-cell recognition (B) A slimy coat that prevents cells from sticking to one another (C) Protection from mechanical and chemical damage (D) All of the above
(D) All of the above
The Na+ electrochemical gradient established by the Na+ pumps in the plasma membrane allows animal cells to: (A) control their pH. (B) import nutrients, such as sugars and amino acids. (C) propagate electrical signals. (D) stimulate muscle cell contraction. (E) All of the above
(E) All of the above
In this cartoon representation of the structure of ATP synthase, which of the components rotate? 1 1 and 5 2 and 3 2, 3, and 4 4
1 and 5
When fatty acids are oxidized to acetyl CoA, each cycle of the reaction removes how many carbon atoms from the fatty acid molecule? 1 2 3 4 It depends on the initial length of the fatty acid.
2
In one second, a phospholipid molecule in an artificial bilayer may diffuse as far as what distance?
2 microns
How much ATP must be invested during the first part of glycolysis for each molecule of glucose broken down? 1 Molecule 2 Molecules 4 Molecules ∼30 Molecules None
2 molecules
In mitochondria, about how many molecules of ATP can be produced from the complete oxidation of a single glucose molecule? 2 10 30 1000 to 2000 It depends on how many mitochondria are present.
30
The complete oxidation of glucose to H2O and CO2 produces about how many molecules of ATP per molecule of glucose? 2 3 4 30
30
How many steps in glycolysis involve the action of a kinase? 2 3 4 6 10
4
In this cartoon representation of the structure of ATP synthase, which of the components catalyzes the synthesis of ATP? 1 2 3 4 5
4
How thick is the plasma membrane?
50 atoms
In a typical animal cell, approximately how much of the mass of the plasma membrane is constituted by proteins?
50%
Which FRAP curve would show a more rapid recovery of fluorescence: one obtained from a cell membrane that contained a large proportion of saturated fatty acids or one from a cell membrane with a large proportion of unsaturated fatty acids?
A membrane containing a larger proportion of unsaturated fatty acids would show a more rapid recovery in a FRAP study.
An electrochemical gradient has a chemical component and an electrical component. Which of the following will have the largest electrochemical gradient?
A positively charged ion, such as Na+, at high concentration outside the cell
Which is NOT an integral membrane protein?
A protein attached to the membrane by noncovalent interactions with other membrane proteins
Which of the following drives the production of ATP from ADP and Pi by ATP synthase? A Na+ gradient A proton gradient Hydrolysis Phosphorylation Sunlight
A proton gradient
In photosynthesis, what drives the generation of ATP by ATP synthase? A proton gradient across the thylakoid membrane The absorption of light by an adjacent chlorophyll molecule The phosphorylation of ATP synthase The transfer of high-energy electrons to ATP synthase
A proton gradient across the thylakoid membrane
In general, which of the following will diffuse across a lipid bilayer most rapidly?
A small, hydrophobic molecule
Which of the following statements describes the resting membrane potential of a neuron? A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced A voltage difference across the plasma membrane when the neuron has been stimulated A voltage difference across the plasma membrane, with more positive membrane potential inside A voltage difference of 0 millivolts (mV) across the membrane A voltage difference that is chiefly a reflection of the electrochemical Na+ gradient across the plasma membrane
A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced
What is the main chemical energy currency in cells? ATP Glucose High-energy electrons NADH Water
ATP
Which is NOT required for the citric acid cycle to take place? ATP GDP NAD+ O2 Oxaloacetate
ATP
What provides the fuel to convert CO2 into sugars in chloroplasts? A proton gradient across a membrane ATP and NADPH generated in the photosynthetic light reactions ATP generated in cellular respiration
ATP and NADPH generated in the photosynthetic light reactions
Most of the energy released by oxidizing glucose is saved in the high-energy bonds of: ADP and other activated carriers. ATP and other activated carriers. GDP and other activated carriers. H2O and CO2. O2.
ATP and other activated carriers.
The drug 2,4-dinitrophenol (DNP) makes the mitochondrial inner membrane permeable to H+. The resulting disruption of the proton gradient inhibits the mitochondrial production of ATP. What effect does DNP have on the transport of ATP out of the mitochondrial matrix? ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane. ATP transport will decrease because less ATP will be available to diffuse across the inner membrane. ATP transport will increase because ATP synthase will be forced to operate in the "reverse" direction. None, because ATP export is not coupled to the movement of protons across the inner membrane. None, because the inner membrane is permeable to ATP.
ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane.
Which two-carbon molecule enters the citric acid cycle? Acetyl CoA Citrate CO2 Oxaloacetate Pyruvate
Acetyl CoA
The movement of an ion against its concentration gradient is called...
Active transport
The glyceraldehyde 3-phosphate produced by the carbon-fixation cycle can be converted into: (A) droplets of fat that are stored in the chloroplast stroma. (B) granules of starch that are stored in the chloroplast stroma. (C) the disaccharide sucrose in the plant cell cytosol. (D) All of the above (E) B and C
All of the above
What is the fate of pyruvate in the cell? (A) It can be converted to acetyl CoA. (B) It can be converted to alanine. (C) It can be converted to glucose. (D) It can be converted to lactate. (E) All of the above (F) All but C
All of the above
Inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize by...
Allowing an influx of Cl-
What is typically true of ion channels?
They are gated
Which of the following organisms do not have mitochondria in their cells? Animals Bacteria Plants Protozoa Yeast
Bacteria
Why do cells lack membrane transport proteins that are specific for the movement of O2?
Because oxygen dissolves readily in lipid bilayers
Prozac®, among many other drugs, functions by altering neurotransmitter levels in the brain. How does Prozac® work?
By blocking the reuptake of serotonin after it has been released, increasing the amount available in the synapses that use it
The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following? Citrate CO2 Glucose Oxaloacetate Pyruvate
CO2
Synaptic plasticity is largely dependent on the presence of which ion in the postsynaptic cell?
Ca^2+
When an action potential reaches a nerve terminal, what type of voltage-gated channels are opened and result in the fusion of synaptic vesicles with the cell membrane?
Ca^2+
Which of the following statements is true about the concentration of calcium ions in cells? Calcium levels are kept high in the cytosol compared to outside the cell. Calcium levels are kept low in the cytosol compared to outside the cell. Calcium levels are kept the same in the cytosol compared to outside the cell.
Calcium levels are kept low in the cytosol compared to outside the cell.
Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones? Anabolism Canabolism Catabolism Metabolism
Catabolism
Which of the following form tiny hydrophilic pores in the membrane through which solutes can pass by diffusion?
Channels
How do transporters and channels select which solutes they help move across the membrane?
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.
In plants, fats and starch are stored in which part of the cell? Cell wall Chloroplast Cytosol Endoplasmic reticulum Vacuole
Chloroplast
How does cholesterol in animal cell membranes affect the bilayer?
Cholesterol tends to stiffen the bilayer
Which is NOT a mechanism for restricting the movement of proteins in the plasma membrane? Coating proteins with carbohydrates Tethering proteins to the cell cortex Tethering proteins to the extracellular matrix Tethering proteins to the surface of another cell Using barriers such as tight junctions
Coating proteins with carbohydrates
Which is NOT found in a cell membrane? Cholesterol DNA Lipid Protein Sugar
DNA
The plasma membrane is NOT involved in: cell growth and motility. cell recognition. cell signaling. DNA replication import and export of molecules.
DNA replication
Double bonds in hydrocarbon tails have what effect on phospholipid tails and the rigidity of the lipid bilayer?
Double bonds decrease the ability of hydrocarbon tails to pack together, which makes the bilayer less stiff.
In this simplified diagram of the reactions of the carbon-fixation cycle, which step is catalyzed by the enzyme Rubisco? A B C D E
E
Which of the following statements is true about the electron-transport chain? Electrons can gain or lose energy, depending on where they enter along the electron-transport chain. Electrons do not gain or lose energy as they move along the electron-transport chain. Electrons gain energy from some complexes and lose energy to other complexes as they move along the electron-transport chain. Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain. Electrons start out at very low energy and gain energy at each transfer step.
Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain.
When a chlorophyll molecule captures light energy, what form does the energy take? Chemical-bond formation within a molecule in the reaction center of the photosystem Excited electrons Excited protons High-energy bond in ATP New electrons added to the molecule
Excited electrons
On what side of the plasma membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located?
External (noncytosolic) side
During oxidative phosphorylation, why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2? FADH2 and NADH feed their electrons to different carriers in the electron-transport chain. FADH2 has a lower electron affinity than does NADH. FADH2 is less likely than NADH to participate in the electron-transport chain. FADH2 promotes the pumping of more protons than does NADH. NADH donates more electrons to the electron-transport chain than does FADH2.
FADH2 and NADH feed their electrons to different carriers in the electron-transport chain.
Combining CO2 and H2O to make a carbohydrate is an energetically very favorable reaction. False True
False
In plant cells, the citric acid cycle takes place in the chloroplast. False True
False
Metabolism can be tightly regulated because the substrates involved in metabolic reactions are each recognized by only a single, unique enzyme. False True
False
The ATP generated during stage 1 of photosynthesis serves as a major source of energy for a plant cell's metabolic needs. False True
False
The oxygen consumed during the oxidation of glucose in animal cells is returned to the atmosphere as CO2. False True
False
The photosynthetic electron-transport chain includes a single proton pump, which ejects H+ from the chloroplast. False True
False
True or False A symport protein would function as an antiport protein if its orientation in the membrane were reversed.
False
True or False All of the carbohydrates in the plasma membrane face the cell exterior, and the carbohydrates on internal cell membranes face the cytosol.
False
Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle, and (2) a light-sensitive proton pump purified from the prokaryote Halobacterium halobium. In each vesicle, the proton pump is oriented such that it will pump H+ into the vesicle. But the ATP synthase molecules are randomly inserted: half the vesicles will have an ATP synthase that faces inward, and half will have an ATP synthase that faces outward. When ADP and Pi are added to the external medium and the vesicles are exposed to light, what will happen? Half of the ATP synthase molecules will produce ATP, the other half will do nothing. Half of the ATP synthase molecules will produce ATP, the other half will hydrolyze ATP. Half of the ATP synthase molecules will produce ATP, the other half will pump protons into the vesicle. Half of the ATP synthase molecules will produce ATP, the other half will pump protons out of the vesicle. The vesicles will produce twice as much ATP as they would if all the ATP synthase molecules were oriented the same way.
Half of the ATP synthase molecules will produce ATP, the other half will do nothing.
What is the ratio of ATP and ADP concentrations in the cytosol of a cell? High ADP/ATP ratio High ATP/ADP ratio
High ATP/ADP ratio
Which reaction releases the most energy? Hydrolysis of 1,3-bisphosphoglycerate to 3-phosphoglycerate Hydrolysis of ADP to AMP Hydrolysis of ATP to ADP Hydrolysis of glucose 6-phosphate to glucose Transfer of a phosphate group from ATP to glucose
Hydrolysis of 1,3-bisphosphoglycerate to 3-phosphoglycerate
Experiments performed by Hans Krebs in the 1930s revealed that the set of reactions that oxidize food molecules and produce CO2 occurs in a cycle. In one experiment, Krebs exposed pigeon muscles to malonate, a compound that inhibits succinate dehydrogenase—the enzyme that converts succinate to fumarate, indicated in red in the linear representation of the reactions of the citric acid cycle (see figure). Which of the following observations, made in malonate-treated muscle, led Krebs to believe that this set of reactions is cyclical? If citrate were added, succinate would accumulate. If oxaloacetate were added, succinate would accumulate. If succinate were added, fumarate would accumulate. Regardless of what he added, large amounts of oxygen would be consumed. Regardless of what he added, oxaloacetate would accumulate.
If oxaloacetate were added, succinate would accumulate.
The chemistry of many metabolic reactions was deciphered using molecules labeled with radioactive isotopes. If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after one turn of the cycle? In acetyl CoA In citrate In CO2 In oxaloacetate In oxaloacetate and in CO2
In oxaloacetate
If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after two turns of the cycle? In acetyl CoA In CO2 In malate In oxaloacetate In oxaloacetate and in CO2
In oxaloacetate and in CO2
In an animal cell, where are the proteins of the electron-transport chain located? In the ER membrane In the mitochondrial inner membrane In the mitochondrial matrix In the mitochondrial outer membrane In the plasma membrane
In the mitochondrial inner membrane
Which of the following statements is true? Inside the cell, the quantity of positively charged ions is almost equal to the quantity of negatively charged ions. Inside the cell, the quantity of positively charged ions is much greater than the quantity of negatively charged ions. Inside the cell, the quantity of positively charged ions is much less than the quantity of negatively charged ions. Inside the cell, there are no negatively charged ions. Inside the cell, there are no positively charged ions.
Inside the cell, the quantity of positively charged ions is almost equal to the quantity of negatively charged ions.
The inside of a cell... Has the same charge as the outside of the cell. Is slightly more negative than the outside of a cell. Is slightly more positive than the outside of a cell.
Is slightly more negative than the outside of a cell.
What type of enzyme catalyzes the rearrangement of chemical bonds within a single molecule? Dehydrogenase Isomerase Kinase Mutase Scramblase
Isomerase
Which statement about phospholipids and detergents is NOT true? Detergents are shaped like cones, whereas phospholipids are more cylindrical. Phospholipids are amphipathic, whereas detergents are hydrophobic. Phospholipids form bilayers in water, whereas detergents tend to form micelles. Phospholipids have two hydrocarbon tails, whereas detergents have just one.
Phospholipids are amphipathic, whereas detergents are hydrophobic
Which of the following will produce the most fluid lipid bilayer? Large amounts of cholesterol Phospholipids with fully saturated tails of 18 carbon atoms Phospholipids with fully saturated tails of 20 carbon atoms Phospholipids with tails of 18 carbon atoms and two double bonds Phospholipids with tails of 20 carbon atoms and two double bonds
Phospholipids with tails of 18 carbon atoms and two double bonds
Which photosystem is able to boost electrons to the very high energy level needed to make NADPH from NADP+? Photosystem I Photosystem II
Photosystem I
All other factors (e.g., concentration and solute size) being equal, which type of solute does a cell tend to pull inside?
Positively charged solutes
Some types of bacteria can survive under both aerobic and anaerobic conditions. Regardless of whether oxygen is present, these cells maintain a proton gradient across the plasma membrane to drive ATP synthesis and the import of nutrients. Under aerobic conditions, a H+ gradient across the plasma membrane is produced by the transfer of electrons along the respiratory chain. When oxygen is present, what do you think takes place in the plasma membrane of these bacteria? ATP synthase hydrolyzes ATP, pumping protons into the cell to help maintain the H+ gradient. ATP synthase hydrolyzes ATP, pumping protons out of the cell to help maintain the H+ gradient. Nutrients are imported by carriers that take advantage of the proton gradient produced by electron transport along the mitochondrial membrane. Protons flow into the bacterium through ATP synthase, generating ATP. Protons flow out of the cell through ATP synthase, generating ATP.
Protons flow into the bacterium through ATP synthase, generating ATP.
Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what?
Pump H+ out of the cell to generate a H+ gradient across the plasma membrane
In cells that cannot carry out fermentation, which products derived from glycolysis would accumulate under anaerobic conditions? Glucose 6-phosphate and NADH Glucose and NADH Lactate and NAD+ Pyruvate and NAD+ Pyruvate and NADH
Pyruvate and NADH
Chlorophyll molecules absorb which color of light most strongly? Black Green Red UV White
Red
Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment?
Removing the double bonds by adding hydrogen (which converts double bonds to single bonds)
Carbon fixation occurs in the second stage of photosynthesis, during the so-called "dark reactions" of the Calvin cycle. In the first step of this cycle, the enzyme Rubisco adds CO2 to the energy-rich compound ribulose 1,5-bisphosphate, ultimately producing two molecules of 3-phosphoglycerate. In a culture of green alga that is carrying out photosynthesis in the presence of CO2 in the laboratory, what would happen to the levels of ribulose 1,5-bisphosphate and 3-phosphoglycerate in the minutes after the lights were turned off and the cultures were plunged into darkness? Both would accumulate. Both would be depleted. Nothing would happen because the Calvin cycle is not dependent on light. Ribulose 1,5-bisphosphate would accumulate, but 3-phosphoglycerate would be depleted. Ribulose 1,5-bisphosphate would be depleted, but 3-phosphoglycerate would accumulate.
Ribulose 1,5-bisphosphate would be depleted, but 3-phosphoglycerate would accumulate.
What type of enzyme moves randomly selected phospholipids from one monolayer of a lipid bilayer to the other?
Scramblase
Which of the following statements is NOT true regarding active transport by transmembrane pumps? Some solutes are moved across a membrane against their concentration gradient using energy from sunlight. Some solutes are moved against their concentration gradient, from one side of a membrane to the other, using energy from ATP hydrolysis. Some solutes are transported across the membrane in tandem with another molecule, both moving from lower concentration to higher concentration.
Some solutes are transported across the membrane in tandem with another molecule, both moving from lower concentration to higher concentration.
Which of the following is true? Fats are converted to acetyl CoA but sugars are not. Fats are converted to acetyl CoA in the mitochondria; sugars are converted to acetyl CoA in the cytosol. Sugars and fats are both converted to acetyl CoA in the mitochondria. Sugars are converted to acetyl CoA but fats are not. Sugars are converted to acetyl CoA in the mitochondria; fats are converted to acetyl CoA in the cytosol.
Sugars and fats are both converted to acetyl CoA in the mitochondria.
What is the name of the specialized junction between a neuron and a target cell?
Synapse
What occurs when ATP synthase operates "in reverse" and pumps H+ across a membrane against its electrochemical proton gradient? The ATP synthase catalyzes the formation of ATP from ADP and Pi. The ATP synthase hydrolyzes ATP to form ADP and Pi. The ATP synthase transports ATP across the membrane. The ATP synthase transports Na+ in the opposite direction across the membrane. The ATP synthase transports nutrients in the opposite direction across the membrane.
The ATP synthase hydrolyzes ATP to form ADP and Pi.
Fluorescence recovery after photobleaching (FRAP) is used to monitor the movement of fluorescently labeled molecules within the plane of a cell membrane. The molecules labeled are often proteins, but can also be lipids. How would the curve that represents FRAP for labeled proteins compare to the curve representing labeled lipids?
The FRAP curve for lipids would show very rapid recovery to initial levels of fluorescence.
Which of the following activities helps restores the ion gradients across the plasma membrane of an axon after an action potential has occurred?
The action of Na+ pumps
In the technique called optogenetics, light-gated Na+ channels are introduced into the brains of living animals. Activation of these channels by light can depolarize the membranes of neurons that contain them, selectively activating these target cells. Since its inception, optogenetics has been expanded to include other types of light-gated channels, such as a channel that is selective for Cl- instead of Na+. If this light-gated Cl- channel were introduced into neurons in a region of the brain that stimulates feeding, what might you expect to see?
The animals would avoid eating, even when they are hungry—but only when the channels are activated by light.
What does it mean for a bond to be "high energy," such as the bonds between phosphate groups in ATP? The bond involves an extra electron. The bond is strong and difficult to break. The bond is strong but easy to break. The hydrolysis of the bond is energetically favorable. The hydrolysis of the bond is energetically unfavorable.
The hydrolysis of the bond is energetically favorable.
Why do phospholipids form bilayers in water?
The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
Which of the following inhibits inorganic ions, like Na+ and Cl-, from passing through a lipid bilayer?
The hydrophobic interior of the lipid bilayer
Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell? The mitochondrion The cytosol The endoplasmic reticulum The Golgi apparatus
The mitochondrion
Which of the following requires an input of energy to occur? The movement of a solute from a region of higher concentration on one side of a membrane to a region of lower concentration on the other side. The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side.
The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side.
During an action potential, which of the following actions does not help return the membrane to its resting potential?
The opening of voltage-gated Na+ channels
In the absence of oxygen, in cells that cannot carry out fermentation, glycolysis would halt at which step? The first step The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate The phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate The reversible rearrangement of glucose 6-phosphate to fructose 6-phosphate The transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP to form ATP
The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate
What does the term gluconeogenesis refer to? The breakdown of glucose during fermentation The breakdown of glucose during glycolysis The release of glucose from molecules such as glycogen The synthesis of glucose from small organic molecules such as pyruvate The transport of glucose across a cell membrane
The synthesis of glucose from small organic molecules such as pyruvate
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, a 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?
The transporter oscillates randomly between states in which it is open to either the extracellular space or the cytosol.
In a patch of animal cell membrane about 10 µm2 in area, which will be true? Given the fluidity of the lipid bilayer, there is no way to predict the relative numbers of proteins and lipids in any patch of cell membrane. There will be an equal number of proteins and lipids. There will be more carbohydrates than lipids. There will be more lipids than proteins. There will be more proteins than lipids.
There will be more lipids than proteins.
Which of the following is NOT true of mitochondria? Inside a cell, they are mobile, constantly changing shape and position. They are replaced by chloroplasts in plants. They are similar in size and shape to bacteria. They contain an outer membrane, an inner membrane, and two internal compartments. They contain their own DNA and RNA.
They are replaced by chloroplasts in plants.
For each molecule of acetyl CoA that enters the citric acid cycle, what activated carriers are produced? Three NADH, one FAD, one GTP Three NADH, one FADH2, one GTP Three NADH, two FADH2, one GTP Three NADPH, one FADH2, one GTP Two NADH, one FADH2, one GTP
Three NADH, one FADH2, one GTP
Which of the following mechanisms prevents osmotic swelling in plant cells?
Tough cell walls
Which type of membrane transport protein can perform either passive or active transport?
Transporters
Both plants and animals store fats in the form of triacylglycerol. False True
True
Each of the three respiratory enzyme complexes includes metal atoms that are tightly bound to the proteins. False True
True
Glycolysis can continue in the absence of oxygen, but only in cells that can carry out fermentation. False True
True
Mitochondria can change their location, shape, and number in the cell to suit the needs of a cell. False True
True
The O2 released to the atmosphere by photosynthesis in chloroplasts is consumed by oxidative phosphorylation in mitochondria. False True
True
The chlorophyll special pair in photosystem I actually serves as the final electron acceptor in the photosynthetic electron-transport chain that carries electrons from photosystem II. False True
True
The electrochemical proton gradient can drive the active transport of metabolites into and out of the mitochondrial matrix. False True
True
The outer membrane of a mitochondrion is permeable to all small molecules, including small proteins. False True
True
To move a proton from one side of a membrane to the other, an electron carrier must be oriented in such a way that it accepts an electron (along with a H+ from water) on one side of the membrane and then releases the H+ on the other side of the membrane as it passes the electron to the next carrier. False True
True
True or False Communication between neurons involves an interconversion of electrical and chemical signals.
True
True or False Given enough time, virtually any molecule will diffuse across a lipid bilayer.
True
True or False Patch-clamp recording can be used to observe the transport of ions through individual ion channels.
True
True or False The glucose-Na+ symport in epithelial cells uses the electrochemical gradient of Na+ to draw glucose into the cell.
True
True or False Transmitter-gated ion channels are insensitive to membrane potential; in the absence of neurotransmitters, they cannot generate an action potential.
True
Which has a larger number of double bonds? Butter Lard Margarine Saturated fats Vegetable oil
Vegetable oil
Which type of ion channel plays the major role in propagating electrical signals in nerve cells?
Voltage-gated
Which of the following statements is NOT true of electron transfer in the electron-transport chain? Each electron transfer is an oxidation-reduction reaction. Electrons move toward molecules with a high redox potential. NADH has a relatively low electron affinity. NADH is a strong electron donor. When an electron carrier accepts an electron, it becomes oxidized.
When an electron carrier accepts an electron, it becomes oxidized.
When an electron is removed from the reaction center of photosystem II, how is the missing electron then replenished? With an electron from a hydrogen ion With an electron from sunlight With an electron removed from photosystem I With an electron removed from water
With an electron removed from water
To explore how yeast cells metabolize glucose, investigators examine the effect the sugar has on the expression of a variety of genes using a DNA microarray. Cultured yeast cells are supplemented with high concentrations of glucose. mRNAs are extracted from the cells, converted into cDNAs, and labeled with a fluorescent marker. The samples are then hybridized to a DNA microarray that includes probes representing yeast genes. Shown here is a data set representing genes involved in ribosome biogenesis and electron-transport. Red indicates that glucose has increased the expression of the genes, whereas green indicates that glucose has decreased gene expression. Based on these data, what can be concluded about how yeast cells behave when grown in the presence of high concentrations of glucose? Yeast cells consume large amounts of oxygen as they break down glucose. Yeast cells exposed to high concentrations of glucose grow by fermentation. Yeast cells extract the maximum amount of energy from glucose via oxidative phosphorylation. Yeast cells grow poorly in high concentrations of glucose. Yeast cells shut down protein synthesis when grown in the presence of high concentrations of glucose.
Yeast cells exposed to high concentrations of glucose grow by fermentation.
As electrons move through the electron-transport chain, they are passed from: a carrier molecule of higher electron affinity to a carrier molecule of lower electron affinity. a carrier molecule of lower electron affinity to a carrier molecule of higher electron affinity.
a carrier molecule of lower electron affinity to a carrier molecule of higher electron affinity.
In the first step of the citric acid cycle: a two-carbon molecule is combined with a four-carbon molecule to form citrate. ATP is consumed. CO2 is released. NADH is produced. two molecules of acetyl CoA combine to form oxaloacetate.
a two-carbon molecule is combined with a four-carbon molecule to form citrate.
Channelrhodopsin can be used to manipulate the activity of neurons because...
channelrhodopsin, when activated by light, depolarizes the membrane and stimulates neurons
When transmitter-gated ion channels in the membrane of a postsynaptic cell open in response to neurotransmitter binding, they...
alter the ion permeability of the postsynaptic membrane, which in turn may depolarize the postsynaptic membrane.
The entire phospholipid molecule is...
amphipathic
During photosynthesis, charge separation takes place when: an excited chlorophyll special pair passes an electron to a set of electron carriers in the antenna complex, leaving behind a negative charge. an excited chlorophyll special pair passes an electron to a set of electron carriers in the antenna complex, leaving behind a positive charge. an excited chlorophyll special pair passes an electron to a set of electron carriers in the reaction center, leaving behind a negative charge. an excited chlorophyll special pair passes an electron to a set of electron carriers in the reaction center, leaving behind a positive charge. energy jumps randomly from one chlorophyll molecule to another in the antenna complex. light energy is captured by a chlorophyll molecule in the antenna complex.
an excited chlorophyll special pair passes an electron to a set of electron carriers in the reaction center, leaving behind a positive charge.
ATP synthase: can break down ATP but cannot produce it. can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient. can produce ATP but cannot break it down.
can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient.
The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called the...
cell cortex
NADH has a strong tendency to: accept electrons. donate electrons. either donate or accept electrons depending on the electrochemical proton gradient.
donate electrons.
The organelles that produce ATP in eukaryotic animal cells: evolved from bacteria engulfed by ancestral cells billions of years ago. harbor eukaryotic-like biosynthetic machinery for making RNA. have a separate set of DNA that contains many of the same genes found in the nucleus. reproduce sexually.
evolved from bacteria engulfed by ancestral cells billions of years ago.
During stage 1 of photosynthesis, excited electrons move: from an electron carrier to NADP+ to ATP synthase. from NADP+ to a mobile electron carrier to the chlorophyll special pair. from sunlight to the chlorophyll special pair. from the chlorophyll special pair to an electron carrier to NADP+. from the stroma to the thylakoid membrane to the thylakoid space.
from the chlorophyll special pair to an electron carrier to NADP+.
It is energetically favorable for protons to flow: from the intermembrane space to the mitochondrial matrix. from the mitochondrial matrix to the intermembrane space.
from the intermembrane space to the mitochondrial matrix.
The electron-transport chain pumps protons: from the cytosol to the intermembrane space. from the intermembrane space to the cytosol. from the intermembrane space to the matrix. from the matrix to the cytosol. from the matrix to the intermembrane space.
from the matrix to the intermembrane space.
The water-splitting step in photosynthesis: (A) consumes protons and thereby depletes the proton gradient across the thylakoid membrane. (B) generates essentially all of the O2 in the Earth's atmosphere. (C) is catalyzed by an enzyme containing an iron-sulfur cluster. (D) occurs on the stromal side of the thylakoid membrane. (E) takes place during the dark reactions. (F) All of the above
generates essentially all of the O2 in the Earth's atmosphere.
When food is plentiful, animals can store glucose as: (A) acetyl CoA. (B) glucose 6-phosphate. (C) glycogen. (D) starch. (E) All of the above
glycogen.
Useful energy is obtained by cells when sugars derived from food are broken down by: gluconeogenesis, fermentation, and the citric acid cycle. gluconeogenesis, the citric acid cycle, and oxidative phosphorylation. glycolysis, the Calvin cycle, and oxidative phosphorylation. glycolysis, the citric acid cycle, and gluconeogenesis. glycolysis, the citric acid cycle, and oxidative phosphorylation.
glycolysis, the citric acid cycle, and oxidative phosphorylation.
When nutrients are plentiful, plants can store glucose as: (A) fats. (B) glucose 6-phosphate. (C) glycogen. (D) starch (E) All of the above
starch
During very active periods of photosynthesis, the glyceraldehyde 3-phosphate generated by carbon fixation in the chloroplast stroma is stored as: ATP. glycogen. pyruvate. starch.
starch.
The synthesis of ATP in glycolysis occurs by: oxidative phosphorylation. oxidative prestidigitation. substrate-level phosphorylation. substrate-level prestidigitation.
substrate-level phosphorylation.
Investigators purify mitochondria from mammalian liver cells. They incubate these mitochondria in the absence of oxygen and the presence of succinate, an intermediate produced during the citric acid cycle. Under these conditions, succinate will donate electrons to the electron-transport chain, thereby reducing the electron carriers in the chain almost completely. When oxygen is then introduced, the carriers become oxidized at different rates, as shown by the colored curves in the figure. Based on the rates of oxidation, in what direction do electrons pass along the electron-transport chain? (For simplicity, the carriers are represented by the numbers 1-4.) O2 → 1 → 2 → 3 → 4 → succinate O2 → 4 → 3 → 2 → 1 → succinate succinate → 1 → 2 → 3 → 4 → O2 succinate → 4 → 3 → 2 → 1 → O2 succinate → O2 → 4 → 3 → 2 → 1
succinate → 1 → 2 → 3 → 4 → O2
Photosynthesis allows plants to capture energy from sunlight to produce: chlorophyll. CO2. H2O. NADH. sugars.
sugars
Which term describes a coupled transporter that moves both solutes in the same direction across a membrane?
symport
The direction that glucose is transported across the membrane is determined by...
the concentration gradient
In eukaryotic cells, new phospholipids are manufactured by enzymes bound to...
the cytosolic face of the endoplasmic reticulum.
The NADH generated during glycolysis feeds its high-energy electrons to: ADP. FAD+. H2O. the citric acid cycle. the electron-transport chain.
the electron-transport chain.
Which portion of a membrane phospholipid faces the outside of the membrane?
the head
Osmosis can be described as...
the movement of water from an area of low solute concentration to an area of high solute concentration.
When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face...
the outside of the cell
In the α helices of transmembrane proteins, the hydrophobic side chains are facing...
the outside of the membrane-spanning helix
The phosphorylation of glucose in step 1 of glycolysis: has a ΔGo of 8 kcal/mole. is carried out by an enzyme called phosphoglucokinase. is energetically unfavorable. traps the sugar inside the cell. will not occur in the absence of NADH.
traps the sugar inside the cell.
In chloroplasts, the pigment chlorophyll donates electrons to an electron-transport chain in the thylakoid membrane. False True
true
Ubiquinone has a redox potential of +30 mV, while cytochrome c has a redox potential of +230 mV. In the electron-transport chain, electrons flow from: cytochrome c to ubiquinone. ubiquinone to cytochrome c.
ubiquinone to cytochrome c.
Following an action potential, a nerve cell goes through a brief refractory period during which it cannot be stimulated. In this refractory period...
voltage-gated Na+ channels in the nerve cell membrane are inactivated.
The oxygen atoms required for the citric acid cycle to produce CO2 ultimately derive from: glucose. molecular oxygen. oxaloacetate. the mitochondrial membrane. water.
water
Which has the highest redox potential? Ferredoxin NADPH Plastocyanin Plastoquinone Water
water
In a lipid bilayer, lipids rapidly diffuse...
within the plane of their own monolayer