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Which molecule is the final electron acceptor in respiration?​

	a.	​water
	b.	​ATP
	c.	​carbon dioxide
	d.	​oxygen
	e.	​hydrogen

d

Glycolysis, pyruvate oxidation, and the citric acid cycle all produce ____.​

	a.	​CO2
	b.	​H2O
	c.	​ATP
	d.	​FADH2
	e.	​NADH

e

Compared to the mitochondrial intermembrane space, the mitochondrial matrix could be described as having ____ pH and _____ pyruvate concentration.​

	a.	​a lower; higher
	b.	​a higher; higher
	c.	​a lower; lower
	d.	​a higher; lower
	e.	​the same;  the same

d

What are the functions of cytochrome c and ubiquinone?​

	a.	​They translocate protons from the matrix to the inner mitochondrial space.
	b.	​They shuttle electrons between the protein complexes.
	c.	​They synthesize water from molecular oxygen.
	d.	​They produce ATP by substrate-level phosphorylation.
	e.	​They produce ATP by oxidative phosphorylation.

b

Free radicals, highly reactive species with unpaired electrons that damage molecules and cells, and can contribute to aging. Coenzyme Q (also known as ubiquinone or CoQ) is often found in lotions and moisturizers. Given what you know about the role of CoQ in cellular respiration, why would it be added to these products?​

	a.	​It recruits free radicals to help increase the rate of glycolysis in skin cells.
	b.	​It absorbs free radicals that can cause damage to skin cells.
	c.	​Removing free radicals decreases the rate of metabolism and slows growth of skin cells.
	d.	​It allows for the regeneration of new skin cells.
	e.	​It drives the spontaneous death of older skin cells that have accumulated too many free radicals.

b

 The enzyme succinate dehydrogenase, located in the inner mitochondrial membrane, is directly involved in ____.​

	a.	​glycolysis and pyruvate oxidation
	b.	​pyruvate oxidation and citric acid cycle
	c.	​citric acid cycle and electron transfer system
	d.	​electron transfer system and glycolysis
	e.	​electron transfer system and fermentation

c

What is directly responsible for pumping protons out of the mitochondrial matrix?​

	a.	​protein complexes I, II, III, and IV
	b.	​cytochrome c and ubiquinone
	c.	​protein complexes I and III
	d.	​protein complexes I, III, and IV
	e.	​NADH and FADH2

d

What is the proton-motive force?​

	a.	​the force needed to move protons into the inner mitochondrial space
	b.	​the amount of energy required to protonate a glucose molecule
	c.	​the free energy associated with the removal of hydrogen from NADH
	d.	​the combination of a proton and voltage gradient across the inner mitochondrial membrane
	e.	​the synthesis of ATP from a proton gradient

d

What powers ATP synthase directly?​

	a.	​electron transfer
	b.	​NADH and FADH2
	c.	​carbohydrate metabolism
	d.	the proton gradient​
	e.	​protein complexes

d

Where is ATP synthase located in non-photosynthetic eukaryotes?​

	a.	​outer membrane of the cell
	b.	​nuclear envelope
	c.	​rough endoplasmic reticulum
	d.	​matrix of the mitochondria
	e.	​inner mitochondrial membrane

e

What directly supplies the electrons for the electron transfer system?​

	a.	​ATP and ADP
	b.	​FADH2 and NADH
	c.	​pyruvate and acetate
	d.	​various enzymes
	e.	​oxygen and water

b

To reach the mitochondrial matrix, protons travel through a channel made by the ____ of ATP synthase.​

	a.	​basal unit
	b.	​headpiece
	c.	​stalk
	d.	​lollipop
	e.	​three catalytic sites

a

When the H⁺ concentration is significantly higher in the mitochondrial matrix than the intermembrane space, ATP synthase would ____.​

	a.	​require an ion to stabilize it
	b.	​no longer function properly
	c.	​hydrolyze ATP to form ADP to pump protons out of the matrix
	d.	​generate ATP to pump protons into the matrix
	e.	​be uncoupled from the electron transport chain

c

Which part of the ATP synthase is responsible for catalyzing ATP formation?​

	a.	​the basal unit
	b.	​the headpiece
	c.	​the stalk
	d.	​the lollipop
	e.	​the electrons

b

A typical eukaryotic cell that has an abundant supply of glucose and O₂ will generate a proton gradient in its mitochondria by ____ that is used primarily for ____.​

	a.	​chemiosmosis; substrate-level phosphorylation
	b.	​the electron transport chain; chemiosmosis
	c.	​the electron transport chain; substrate-level phosphorylation
	d.	​fermentation; NAD reduction
	e.	​glycolysis; production of CO2

b

What is one potential fate for a proton in the mitochondrial matrix?​

	a.	​They are attached to NAD+ and FAD.
	b.	​They combine with oxygen to form water.
	c.	​They synthesize ATP by substrate-level phosphorylation.
	d.	​They help in the production of CO2.
	e.	​They regenerate Coenzyme A.

b

Why does NADH produce more energy than FADH₂?​

	a.	​FADH2 donates electrons to protein complex III as opposed to complex II.
	b.	​FADH2 requires more ATP to produce it and gives more energy back.
	c.	​NADH and FADH2 are synthesized in different steps of cellular respiration.
	d.	​NADH has a high free energy and can be oxidized more readily than FADH2.
	e.	​NADH supplies fewer electrons that are of a higher energy state than FADH2.

d

In order to completely oxidize glucose, it takes two turns of the citric acid cycle, which yields a net of 2 ATP, 6 NADH and 2 FADH₂. How many of the 32 total ATP molecules produced in cellular respiration come from the citric acid cycle, including the contribution from the NADH and FADH₂?​

	a.	​32
	b.	​28
	c.	​24
	d.	​20
	e.	​16

d

How efficient is cellular respiration in extracting the energy stored in the bonds of glucose?​

	a.	​25%
	b.	​33%
	c.	​45%
	d.	​50%
	e.	​80%

b

Suppose a human metabolic disease only allows electrons to be used from NADH and not FADH₂.  What is a probable cause of this disease?​

	a.	​a defect in assembly protein genes for complex II of the electron transfer system
	b.	​enzyme defects in glycolysis and the citric acid cycle
	c.	​a deficient amount of cytochrome c and coenzyme Q
	d.	​improper regulation of phosphofructokinase
	e.	​inability of oxygen to act as a final electron acceptor

a

Suppose we hypothesize that potato plants use uncoupling proteins (UCPs) in a similar way as mammals. What would be the evidence to support this hypothesis?​

	a.	​increased amounts of ATP production
	b.	​decreased sugar metabolism
	c.	​increased internal tissue temperature
	d.	​decreased mitochondrial catabolism
	e.	​increased cytosolic pH

c

Racker and Stoeckenius used synthetic phospholipid membrane vesicles that contained a light-activated protein pump and ATP synthase to test Mitchell's chemiosmotic hypothesis. What was the conclusion of this experiment?​

	a.	​Phospholipid membrane vesicles require a proton gradient to maintain integrity.
	b.	​ATP synthase is powered by the proton-motive force.
	c.	​ATP synthase can generate a proton gradient.
	d.	​Light-activated proton pumps can generate a proton gradient.
	e.	​Light-activated proton pumps interact with ATP synthase to modulate its activity.

b

A patient with a mitochondrial disease is found to have a mutation in Gene X. A homologous gene in a Drosophila (fruit fly), did not cause a similar deficit. What does this suggest?​

	a.	​Gene X is highly conserved between humans and Drosophila.
	b.	​Gene X is not conserved between humans and Drosophila.
	c.	​Gene X is encoded in nuclear DNA.
	d.	​Gene X is encoded in mitochondrial DNA.
	e.	​Gene X is a redundant protein in Drosophila.

b

As a result of fermentation, cells produce ____.​

	a.	​ADP
	b.	​NADH
	c.	​FAD
	d.	​O2
	e.	​NAD+

e

In the absence of O₂, the partial metabolism of glucose in human muscles produces _____.​

	a.	​acetaldehyde
	b.	​carbon dioxide
	c.	​energy
	d.	​lactic acid
	e.	​oxygen

d

After one minute without oxygen, brain cells begin to die. After three minutes, this damage is likely to cause severe neurological deficits. The dependence of brain cells on oxygen for survival indicates that these cells are ____.​

	a.	​strict aerobes
	b.	​strict anaerobes
	c.	​facultative aerobes
	d.	​facultative anaerobes
	e.	​transitional aerobes

a

Anaerobic respiration produces ATP by _____.​

	a.	​glycolysis only
	b.	​glycolysis and the Krebs only
	c.	​glycolysis, the Krebs and electron transport chain with inorganic molecules as a final acceptor
	d.	​glycolysis, the Krebs and electron transport chain with organic molecules as a final acceptor
	e.	​electron transport chain with organic molecules as a final acceptor only

c

The Warburg effect is the observation that cancer cells produce energy using a high rate of glycolysis followed by fermentation rather than oxidative phosphorylation. Although the exact cause is still under investigation, which explanation is most plausible?​

	a.	​Tumors attract blood vessels to increase levels of available oxygen.
	b.	​In order to grow quickly, high levels of ATP are required.
	c.	​Mutations in phosphofructokinase prevent feedback inhibition.
	d.	​Tumor formation upregulates glycolytic proteins.
	e.	​Rapid cell proliferation damages mitochondrial function.

e

About 10-20% of patients with Leigh Syndrome, a mitochondrial disease, have a mutation in MT-ATP6, a gene that codes for ATP synthase. These patients often experience high levels of _____ in their cells due to an increase in levels of pyruvate that are unable to convert to acetyl-CoA.​

	a.	​NADH
	b.	​FADH2
	c.	​lactate
	d.	​ethanol
	e.	​carbon dioxide

c

Some organisms are not able to live in an environment where there is oxygen; these types of organisms are called obligate anaerobes. Which explanation is most plausible for how they survive without oxygen?​

	a.	​They are able to survive using less energy than aerobes.
	b.	​All of their ATP is imported into the cell from an external source.
	c.	​Sulfur is used instead of oxygen because it is chemically similar.
	d.	​These organisms use photosynthesis to produce energy.
	e.	​Their mitochondria are damaged, and consequently they are short-lived.

c

Which enzyme in the glycolytic pathway acts as a switch that can be regulated by ATP, AMP, and citrate?

	a.	​pyruvate kinase
	b.	​triosephosphate isomerase
	c.	​aldolase
	d.	​ATP synthase
	e.	​phosphofructokinase

a

We study cellular respiration because it is one of the most important pathways in biology. In fact, nearly all carbohydrates at some point in their catabolism are directed through cellular respiration. Why is it unnecessary to have multiple independent pathways to break down different molecules?​

	a.	​Using cellular respiration is theoretically the most efficient way to break down sugars and other molecules.
	b.	​Oxygen must be used in the breakdown of all molecules in order to yield ATP.
	c.	​Greater complexity would lead to an eventual failure of the biological system.
	d.	​Most biological cells only catabolize one or two different types of sugars and only need one main pathway.
	e.	​Energy-containing macromolecules can be converted to products that can enter at various points in the cellular respiration pathway.

e

The oxidation of which macromolecule yields the most energy by weight?​

	a.	​lipids
	b.	​glycogen
	c.	​starch
	d.	​glucose
	e.	​protein

a

Glucose biosynthesis is called _____.​

	a.	​glyconeogenesis
	b.	​fatty acid oxidation
	c.	​glycolysis
	d.	​pentose phosphate pathway
	e.	​gluconeogenesis

e

When ATP levels are high, which enzyme's activity will be directly decreased by feedback inhibition?​

	a.	​aconitase
	b.	​malate dehydrogenase
	c.	​citrate synthase
	d.	​isocitrate dehyrogenase
	e.	​fumerase

c

Which molecule stimulates phosphofructokinase to increase the flow of intermediates through glycolysis?​

	a.	​NADH
	b.	​FADH2
	c.	​ATP
	d.	​AMP
	e.	​acetyl CoA

d

When triglycerides are hydrolyzed, they are broken down into glycerol and fatty acids. The fatty acids are further broken down into two-carbon fragments in a process called fatty acid oxidation. At which pathway do these fragments enter respiration?​

	a.	​glycolysis
	b.	​pyruvate oxidation
	c.	​citric acid cycle
	d.	​oxidative phosphorylation
	e.	​carbohydrate hydrolysis

c