Cell Bio HW #7

Which is true about electrons as they move through the electron-transport chain? A. Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain. B. Electrons start out at very low energy and gain energy at each transfer step. C. Electrons neither gain nor lose energy as they move along the electron-transport chain. D. Electrons are pumped across the mitochondrial membrane as they move along the electron-transport chain. E. Electrons can gain or lose energy, depending on where they enter along the electron-transport chain.

A. Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain.

The purpose of the photosynthetic reaction center is to convert captured light energy into chemical energy in the form of transferrable excited electrons. Choose all of the statements that correctly describe the photosynthetic reaction center structure. A. It spans the lipid bilayer of the thylakoid membrane. B. It contains four protein subunits. C. It contains one peripheral cytochrome subunit. D. It contains four chlorophyll and four pheophytin molecules.

A. It spans the lipid bilayer of the thylakoid membrane. B. It contains four protein subunits. C. It contains one peripheral cytochrome subunit.

Which activated carriers are produced by the citric acid cycle? A. NADH B. FADH2 C. NADPH D. ATP E. CO2 F. GTP

A. NADH B. FADH2 F. GTP

Why can electron carriers move a proton from one side of a membrane to the other? A. They can accept an electron (along with an H+ from water) on one side of the membrane and then release the H+ on the other side of the membrane as they pass the electron to the next carrier. B. They have a higher affinity for protons than does water. C. They are able to invert their orientation within the membrane, allowing them to pick up a proton from one side of the membrane and release it on the other. D. They have a redox potential higher than that of NADH. E. They have a redox potential lower than that of NADH.

A. They can accept an electron (along with an H+ from water) on one side of the membrane and then release the H+ on the other side of the membrane as they pass the electron to the next carrier.

How do specialized brown fat cells take advantage of oxidative phosphorylation to generate heat?A. They contain a carrier protein that dissipates the proton gradient across the inner mitochondrial membrane. B. They have the ability to carry out photosynthesis. C. They contain a carrier protein that produces a larger proton gradient across the inner mitochondrial membrane. D. They oxidize only sugars, and store all their fat. E. They produce and consume larger than normal amounts of ATP.

A. They contain a carrier protein that dissipates the proton gradient across the inner mitochondrial membrane.

It is energetically favorable for protons to flow in which direction?A. from the intermembrane space to the mitochondrial matrix B. across the outer mitochondrial membrane C. toward the compartment with the lowest pH D. toward the compartment with the most positive charge E. from the mitochondrial matrix to the intermembrane space

A. from the intermembrane space to the mitochondrial matrix

Which of these processes require a membrane? A. generation of energy by mitochondria B. generation of ATP by photosynthesis in bacteria C. generation of ATP by photosynthesis in plants D. generation of ATP by oxidative phosphorylation E. generation of ATP by glycolysis

A. generation of energy by mitochondria B. generation of ATP by photosynthesis in bacteria C. generation of ATP by photosynthesis in plants D. generation of ATP by oxidative phosphorylation

In the electron-transport chain, as electrons move along a series of carriers, they release energy that is used to do what? A. pump protons across a membrane B. hydrolyze ATP C. oxidize food molecules D. phosphorylate ADP to form ATP E. split water into protons and oxygen

A. pump protons across a membrane

ATP synthase is a large molecular machine that converts the energy in an electrochemical gradient into the bond energy stored in ATP. Which of the following events are required for the synthesis of ATP?A. rotation of the rotor in the membrane B. binding of ATP to an empty F1 ATPase subunit C. movement of protons down their gradient through ATP synthase D. conformational changes of the F1 ATPase

A. rotation of the rotor in the membrane C. movement of protons down their gradient through ATP synthase D. conformational changes of the F1 ATPase

During photosynthesis, what happens in the water-splitting step? A. It consumes protons and thereby depletes the proton gradient across the thylakoid membrane. B. It generates essentially all of the O2 in the Earth's atmosphere. C. It takes place during stage 2 of photosynthesis. D. It is catalyzed by an enzyme containing an iron-sulfur cluster. E. It occurs on the stromal side of the thylakoid membrane.

B. It generates essentially all of the O2 in the Earth's atmosphere.

Antimycin A is a piscicide (fish poison) used to manage fisheries and kill invasive species. Antimycin A blocks the transfer of electrons through the cytochrome b-c1 complex. What components of the electron transport chain are bound to high-energy electrons after treating a mitochondrion with antimycin A? A. None of the complexes are bound to high-energy electrons. B. NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the cytochrome c oxidase complex are not. C. O2 and the cytochrome c oxidase complex are bound to high-energy electrons while NADH and the NADH dehydrogenase complex are not. D. All three complexes and NADH are bound to high-energy electrons.

B. NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the cytochrome c oxidase complex are not.

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? A. No, because cows and prokaryotes are so distantly related that their proteins cannot be expected to work together. B. No, because ATP synthase is not oriented correctly. C. Yes, because the proton pump will generate a proton gradient that ATP synthase can use to synthesize ATP. D. No, because protons are small enough to pass freely in and out of an artificial lipid vesicle. E. No, because no electron-transport chain is present.

B. No, because ATP synthase is not oriented correctly.

Protons are pumped across the mitochondrial inner membrane as electrons are transferred through the mitochondrial electron transport chain. Which of the following statements about proton pumping are correct? A. Protons are pumped into the matrix of the mitochondria. B. The mitochondria use the proton gradient to synthesize ATP. C. The pH inside the mitochondrial matrix is higher than in the intermembrane space. D. The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons across the membrane.

B. The mitochondria use the proton gradient to synthesize ATP. C. The pH inside the mitochondrial matrix is higher than in the intermembrane space. D. The NADH dehydrogenase, cytochrome b-c1, and cytochrome oxidase complexes all pump protons across the membrane.

How do the high-energy electrons of activated carriers contribute to forming the high-energy phosphate bonds of ATP? A. They are transferred directly to ADP to form ATP. B. They are used by the electron-transport chain to make a proton gradient. C. They are pumped across the membrane to form an electron gradient. D. They are passed to ATP synthase to power ATP synthesis.

B. They are used by the electron-transport chain to make a proton gradient.

Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms? A. bone deformities B. heart problems C. sterilit D. light sensitivity

B. heart problems

Which metal ion is found in all three respiratory enzyme complexes? A. sulfur B. iron C. copper D. manganese E. heme

B. iron

Approximately how many molecules of ATP can be produced in mitochondria from the complete oxidation of a single glucose molecule? A. 2 B. It depends on the number of mitochondria present C. 30 D. 1000 to 2000 E. 4

C. 30

What happens when ATP synthase operates "in reverse" and pumps H+ across a membrane against its electrochemical proton gradient?A. Na+ is transported in the opposite direction across the membrane. B. ATP is co-transported across the membrane. C. ATP is hydrolyzed to form ADP and Pi. D. Nutrients are transported in the opposite direction across the membrane. E. ATP is synthesized from ADP and Pi.

C. ATP is hydrolyzed to form ADP and Pi.

Suppose the shaft of ATP synthase that is attached to the rotor were truncated (shortened) such that it no longer extended into the F1 ATPase head. What would be the consequence of this mutation? A. Protons would not cross the membrane using the rotor. B. The rotor in the membrane would no longer turn. C. ATP would not be produced because the conformation of the F1 ATPase head would not be changed. D. ATP synthase would work in reverse, breaking down ATP and pumping protons against their gradient.

C. ATP would not be produced because the conformation of the F1 ATPase head would not be changed.

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 outside the vesicle, and the DNP-treated vesicles are exposed to light, will ATP be produced? A. Yes, because H+ can enter the vesicle through DNP. B. Yes, because ATP synthase can operate in reverse, thus maintaining the H+ gradient. C. No, because the DNP will collapse the H+ gradient that ATP synthase uses to generate ATP. D. No, because DNP would allow ADP and Pi to enter the vesicle. E. Yes, because ATP synthase is oriented in such a way that it can use the protons that leave the vesicle through DNP. F. Yes, because DNP cannot prevent light from activating the proton pump.

C. No, because the DNP will collapse the H+ gradient that ATP synthase uses to generate ATP.

In photosynthesis, what drives the generation of ATP by ATP synthase? A. the transfer of high-energy electrons to ATP synthase B. the phosphorylation of ATP synthase C. a proton gradient across the thylakoid membrane D. the absorption of light by a photosynthetic reaction center E. the generation of a charge separation in the photosynthetic reaction center

C. a proton gradient across the thylakoid membrane

Stage 1 of photosynthesis is, in large part, equivalent to what process? A. the carbon-fixation cycle B. glycolysis C. oxidative phosphorylation D. the production of acetyl CoA by the pyruvate dehydrogenase complex E. the citric acid cycle

C. oxidative phosphorylation

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 additional effect would DNP have on the transport of ATP out of the mitochondrial matrix? A. None, because the inner membrane is permeable to ATP. B. None, because ATP export is not coupled to the movement of protons across the inner membrane. C. ATP transport will decrease because less ATP will be available to diffuse across the inner membrane. D. ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane. E. ATP transport will increase because ATP synthase will be forced to operate in the "reverse" direction.

D. ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane.

Which statement regarding the ratio of ATP and ADP concentrations in the cell cytosol is accurate? A. Cells keep the concentration of ADP in the cytosol about 100 times higher than that of ATP. B. The poison cyanide depletes ADP by halting electron transport. C. Cells keep the concentration of ATP in the cytosol about 100 times higher than that of ADP. D. Cells keep the concentration of ATP in the cytosol about 10 times higher than that of ADP. E. The poison cyanide depletes ATP by halting the citric acid cycle. F. Cells keep the concentration of ADP in the cytosol about 10 times higher than that of ATP.

D. Cells keep the concentration of ATP in the cytosol about 10 times higher than that of ADP.

Which of the following statements correctly describes the location of the photosystem I (PSI), photosystem II (PSII), and ATP synthase complexes used in photosynthesis? A. The three complexes are found dispersed throughout the grana and stroma thylakoids. B. PSII is in the stroma thylakoids and grana end membranes, and PSI and ATP synthase are in the grana thylakoid. C. PSII and ATP synthase are in the stroma thylakoids and grana end membranes, and PSI is in the grana thylakoid. D. PSI and ATP synthase are in the stroma thylakoids and grana end membranes, and PSII is in the grana thylakoid.

D. PSI and ATP synthase are in the stroma thylakoids and grana end membranes, and PSII is in the grana thylakoid.

The movement of electrons through the electron-transport chain in mitochondria does which of the following? A. produces oxygen B. pumps ATP across the inner mitochondrial membrane C. produces NADH D. pumps protons out of the mitochondrial matrix E. consumes ATP

D. pumps protons out of the mitochondrial matrix

What is true of stage 2 of photosynthesis? A. It takes place in the chloroplast grana. B. It produces all of the O2 we breathe. C. It begins with the production of ATP and NADPH and ends with their consumption. D. It generates a proton gradient across the thylakoid membrane. E. It produces glyceraldehyde 3-phosphate in the stroma.

E. It produces glyceraldehyde 3-phosphate in the stroma.

Diseases that disrupt the function of mitochondria are particularly harmful to muscle and nerve cells for what reason? A. These cells can produce energy by fermentation. B. These cells lack mitochondria. C. These cells cannot produce energy by fermentation. D. These cells undergo rapid cycles of cell division to function. E. These cells need large amounts of ATP to function normally.

E. These cells need large amounts of ATP to function normally.

Which of the following drives the production of ATP from ADP and Pi by ATP synthase? A. hydrolysis B. sunlight C. a sodium (Na+) gradient D. phosphorylation E. a proton (H+) gradient

E. a proton (H+) gradient