Bio 329 HW 13
For every three molecules of CO2 that enter the carbon-fixation cycle, what is produced and what is consumed?
1 molecule of glyceraldehyde 3-phosphate is produced, and 9 molecules of ATP + 6 molecules of NADPH are consumed.
Approximately how many molecules of ATP can be produced in mitochondria from the complete oxidation of a single glucose molecule?
30
During oxidative phosphorylation, why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2?Choose one:FADH2 is less likely than NADH to participate in the electron-transport chain.NADH donates more electrons to the electron-transport chain than does FADH2.FADH2 promotes the pumping of more protons than does NADH.FADH2 has a lower electron affinity than does NADH.FADH2 and NADH feed their electrons to different carriers in the electron-transport chain
ADH2 and NADH feed their electrons to different carriers in the electron-transport chain
Which activated carrier contains a high-energy bond whose hydrolysis releases a large amount of free energy?
ATP
What provides the fuel to convert CO2 into sugars in chloroplasts?
ATP and NADPH generated in the photosynthetic light reactions
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?
ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane.
Not all fat cells are equivalent. Humans and other animals contain both white fat cells and brown fat cells, named after their color. Because increases in brown fat cells may aid weight loss, researchers are interested in factors that control the ratio of white fat cells and brown fat cells, as detailed in a 2017 article in Obesity Reviews. What is the mechanism for how brown fat cells aid weight loss?
Brown fat cell mitochondria contain an uncoupling protein.
Which is true about electrons as they move through the electron-transport chain?
Electrons start out at very high energy and lose energy at each transfer step along the electron-transport chain.
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.
Which activated carriers are produced by the citric acid cycle?
GTP NADH FADH2
During electron transport, which serves as a ready source for protons that can be pumped across the membrane?
H2O
When an electron is removed from the reaction center of photosystem II, the missing electron is replaced by an electron from which of the following?
H2O
Which is true of ATP synthase?
It can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient.
During photosynthesis, what happens in the water-splitting step?
It generates essentially all of the O2 in the Earth's atmosphere.
Which of the following is true of NADH?
It has a weak affinity for electrons and a negative redox potential.
What happens to the ATP produced during stage 1 of photosynthesis?
It is consumed within the chloroplast to produce glyceraldehyde 3-phosphate.
What is true of the process of combining CO2 and H2O to make a carbohydrate?
It is energetically unfavorable.
When the difference in redox potential between two molecules is highly positive, what is true of the transfer of electrons between them?
It is highly favorable.
In terms of energy production, what is true of cell respiration?
It is more efficient than a gasoline-powered engine.
What is true of stage 2 of photosynthesis?
It produces glyceraldehyde 3-phosphate in the stroma.
What is true of nitrogen fixation?
It reduces N2 to ammonia (NH3).
The electron-transport chain in mitochondria accepts high-energy electrons directly from which molecule?
NADH
Most of the energy for the synthesis of ATP comes from which molecule?
NADH produced by the citric acid cycle
In the electron-transport chain in chloroplasts, which molecule serves as the final electron acceptor?
NADP+
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.
In mitochondria, what is the final electron acceptor in the electron-transport chain?
O2
Why does cytochrome c oxidase bind to oxygen very tightly?
Release of partially reduced oxygen radicals can damage the cell.
Carbon fixation occurs in the second stage of photosynthesis, during the light-independent 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?
Ribulose 1,5-bisphosphate would be depleted, but 3-phosphoglycerate would accumulate.
What could be true of a baby born following mitochondrial replacement therapy, a treatment designed to prevent the transmission of mitochondrial defects?
The baby would have genetic material from three "parents" in each cell.
What is one reason that plants do not generally produce sugars after dark?
The enzymes involved in stage 2 of photosynthesis are inactivated in the dark.
Diseases that disrupt the function of mitochondria are particularly harmful to muscle and nerve cells for what reason?
These cells need large amounts of ATP to function normally.
How do specialized brown fat cells take advantage of oxidative phosphorylation to generate heat?
They contain a carrier protein that dissipates the proton gradient across the inner mitochondrial membrane.
Which of the following statements are true of mitochondria?
They contain an outer membrane, an inner membrane, and two internal compartments. They contain their own DNA and RNA. Inside a cell, they are mobile, constantly changing shape and position. They are similar in size and shape to bacteria.
What is true of the organelles that produce ATP in eukaryotic animal cells?
They evolved from bacteria engulfed by ancestral cells billions of years ago.
What is true of mobile electron carriers?
They ferry electrons between one respiratory complex and the next.
How does the photosynthetic machinery produce enough energy to transfer electrons from H2O to NADPH?
Two photosystems operating in series couple their electron-energizing steps.
Which of the following drives the production of ATP from ADP and Pi by ATP synthase?
a proton (H+) gradient
In photosynthesis, what drives the generation of ATP by ATP synthase?
a proton gradient across the thylakoid membrane
The proton gradient that drives ATP synthesis during photosynthesis is generated by which of the following?
an electron carrier that pumps protons out of the stroma into the thylakoid space
The buildup of lactic and formic acids generated by anaerobic fermentation likely favored the evolution of which of the following?
cells that could pump protons
In a test tube, NADH has a strong tendency to do what?
donate electrons to O2
It is energetically favorable for protons to flow in which direction?
from the intermembrane space to the mitochondrial matrix
The electron-transport chain pumps protons in which direction?
from the matrix to the intermembrane space
The electrochemical proton gradient across the mitochondrial membrane can be used to drive which processes?
import of pyruvate into the mitochondrial matrix export of ATP from the mitochondrial matrix import of ADP into the mitochondrial matrix
In an animal cell, where are the proteins of the electron-transport chain located?
inner mitochondrial membrane
What is true of the antenna complex of a photosystem?
it captures light energy
Stage 1 of photosynthesis is, in large part, equivalent to what process?
oxidative phosphorylation
What serves as the final electron acceptor in the photosynthetic electron-transport chain that carries electrons from photosystem II?
photosystem I
Which of these is able to boost electrons to the very high energy level needed to make NADPH from NADP+?
photosystem I
Which of the following organisms have mitochondria in their cells?
plants animals yeasts protozoa
When protons move down their electrochemical gradient into the mitochondrial matrix, what do they do?
produce ATP
In the electron-transport chain, as electrons move along a series of carriers, they release energy that is used to do what?
pump protons across a membrane
The movement of electrons through the electron-transport chain in mitochondria does which of the following?
pumps protons out of the mitochondrial matrix
Which of the following are consumed as fuel within mitochondria?
pyruvate amino acids fatty acids acetyl CoA
Chlorophyll molecules absorb which color of light most strongly?
red
During very active periods of photosynthesis, the glyceraldehyde 3-phosphate generated by carbon fixation in the chloroplast stroma is stored as which molecule?
starch
Photosynthesis allows plants to capture energy from sunlight to produce what?
sugars
