Question 1

The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. About 10% of Springer spaniels suffer from canine PFK deficiency. Given its critical role in glycolysis, which of the following conditions would be a likely consequence for dogs afflicted with this disorder?
A) They would die as embryos.
B) They would have elevated blood-glucose levels, which may result in a high incidence of diabetes.
C) They would be lethargic and readily tire from exercise.
D) They would carry out elevated levels of oxidative phosphorylation.

Accepted Answer

Since PFK is a key enzyme in glycolysis, its deficiency would impair the production of ATP via anaerobic respiration. This would result in limited energy availability for cells, causing affected dogs to exhibit lethargy and fatigue during exercise.

Question 2

Which of the following metabolic processes normally occurs regardless of whether or not oxygen (O₂) is present?
A) citric acid cycle
B) glycolysis
C) lactate fermentation
D) oxidative phosphorylation

Accepted Answer

Glycolysis is the metabolic process that occurs in the cytoplasm and does not require oxygen, making it anaerobic. It is the first step in both aerobic and anaerobic respiration.

Question 3

An organism is discovered that thrives in both the presence and absence of oxygen. Interestingly, as oxygen is removed from the organism's environment, the rate of sugar consumption increases while the growth rate decreases. What do these observations suggest about the likely identity of this organism?
A) It is an unremarkable eukaryotic organism.
B) It is a photosynthetic organism.
C) It is an obligate anaerobic organism.
D) It is a facultative anaerobic organism.

Accepted Answer

The observations of this organism thriving in both the presence and absence of oxygen, and the increase in sugar consumption and decrease in growth rate as oxygen is removed from the environment, suggest that the organism is able to perform both aerobic respiration and fermentation. This is a characteristic of facultative anaerobic organisms. Option A is unlikely since eukaryotic organisms generally require oxygen for metabolic processes. Option B is unlikely since photosynthetic organisms require a source of light for energy, and there is no mention of light in the scenario. Option C is also unlikely since obligate anaerobic organisms cannot survive in the presence of oxygen.

Question 4

A person on a strict diet and exercise regimen lost 7 kg (about 15 pounds) of body fat in just two weeks. What is the most likely way that the lost fat left the body?
A) It was released as CO₂ and H₂O.
B) It was converted to heat and then released.
C) It was converted to ATP, which weighs much less than fat.
D) It was eliminated from the body as feces.

Accepted Answer

When the body metabolizes fat, it breaks it down into carbon dioxide (CO₂) and water (H₂O), which are then eliminated from the body through breathing, sweating, and urinating. Therefore, the most likely way that the lost fat left the body is by being released as CO₂ and H₂O.

Question 5

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
A) glucose
B) cholesterol
C) fatty acids
D) amino acids

Accepted Answer

Glucose can be catabolized through the process of glycolysis, which does not require mitochondria or oxygen. Yeast cells can generate ATP (energy) through glycolysis alone, even without functional mitochondria. Cholesterol, fatty acids, and amino acids require functional mitochondria for their complete metabolism and hence cannot support the growth of yeast cells with defective mitochondria.

Question 6

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
A) It allows for an increased rate of glycolysis.
B) It allows for an increased rate of the citric acid cycle.
C) It increases the surface for oxidative phosphorylation.
D) It increases the surface for substrate-level phosphorylation.

Accepted Answer

The larger inner mitochondrial membranes provide a greater surface area for oxidative phosphorylation, the process by which ATP is produced through the electron transport chain. This process occurs on the inner mitochondrial membrane and requires a large surface area to facilitate the necessary reactions. This is particularly important in liver cells, which require a large amount of ATP for their metabolic functions.

Question 7

Even though plants cells carry out photosynthesis, they still use their mitochondria for oxidation of pyruvate. Under what conditions will plant cell mitochondria be active in this process?
A) only in photosynthetic cells in the light, while photosynthesis occurs concurrently
B) only in cells that store glucose in the form of starch and only in the dark
C) in all cells, with or without light
D) in photosynthesizing cells in the light, and in other cells in the dark

Accepted Answer

Plant cell mitochondria are always active in the process of oxidative phosphorylation and electron transport chain, regardless of whether there is light or not. Even in the presence of photosynthesis, the plant cell still requires the energy produced by the mitochondria for cellular processes. Therefore, plant cell mitochondria are active in all cells, with or without light.

Question 8

In the absence of oxygen, yeast cells can obtain energy by fermentation, which results in the production of which of the following sets of molecules?
A) ATP, CO₂, and ethanol (ethyl alcohol)
B) ATP, CO₂, and lactate
C) ATP, NADH, and ethanol
D) ATP, CO₂, and acetyl CoA

Accepted Answer

Fermentation by yeast cells in the absence of oxygen results in the production of ATP (energy for the cell) and two waste products: carbon dioxide (CO₂) and ethanol. Option B is incorrect because lactate is produced in animal cells during fermentation, not yeast cells. Option C is incorrect because although NADH is produced during fermentation, it is not one of the final products. Option D is incorrect because acetyl CoA is not a product of fermentation, but rather the starting molecule for cellular respiration when oxygen is present.

Question 9

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. After the disruption, which components involved in oxidative phosphorylation must be present for electron transfer and ATP synthesis to still occur?
A) only the electron transport system
B) only the ATP synthase system
C) all of the electron transport system and the proteins that add CoA to acetyl groups
D) all of the electron transport system and ATP synthase

Accepted Answer

Both the electron transport system and ATP synthase are necessary components of oxidative phosphorylation for electron transfer and ATP synthesis to occur. Therefore, all of the electron transport system and ATP synthase must be present for these processes to still occur after disrupting the inner mitochondrial membranes.

Question 10

Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
A) reduction of NAD⁺ to NADH
B) reduction of FAD to FADH₂
C) oxidation of NADH to NAD⁺
D) hydrolysis of ATP to ADP +  ᵢ

Accepted Answer

The answer of Which of the following statements describes a...

Question 11

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. Which of the following statements about these inside-out membrane vesicles is true?
A) The inside of the vesicles will become acidic when NADH is added.
B) The inside of the vesicles will become alkaline when NADH is added.
C) ATP will be produced from ADP and  ᵢ in the interior of the vesicle.
D) The vesicles will pump protons out of the interior of the vesicle to the exterior using energy from ATP hydrolysis.

Accepted Answer

The answer of Exposing inner mitochondrial membranes to ultrasonic vibrations...

Question 12

What kinds of cells carry out ATP synthesis by chemiosmosis?
A) all cells, both prokaryotic and eukaryotic, exclusively using oxygen as the electron acceptor
B) only animal cells in mitochondria, exclusively using oxygen as the electron acceptor
C) only eukaryotic cells, both plant and animal, using either oxygen or other electron acceptors
D) all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors

Accepted Answer

All respiring cells, both prokaryotic and eukaryotic, use chemiosmosis to carry out ATP synthesis, which can occur using either oxygen (aerobic respiration) or other electron acceptors (anaerobic respiration). This includes not just animal cells in mitochondria but also plant cells in chloroplasts and various types of bacteria.

Question 13

What is the oxidizing agent in the following reaction?
Pyruvate + NADH + H⁺ → Lactate + NAD⁺
A) NADH
B) NAD⁺
C) lactate
D) pyruvate

Accepted Answer

The answer of What is the oxidizing agent in the...

Question 14

Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
A) glycolysis and fermentation
B) fermentation and chemiosmosis
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle

Accepted Answer

Glycolysis and fermentation take place in the cytosol of a eukaryotic cell. Fermentation is also possible, but it is not exclusive to the cytosol and can occur in other parts of the cell depending on the type of fermentation. The oxidation of pyruvate to acetyl CoA and the citric acid cycle take place in the mitochondria.

Question 15

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
A) It produces much less ATP than does oxidative phosphorylation.
B) It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.
C) It is present in prokaryotic cells but not in eukaryotic cells.
D) It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells.

Accepted Answer

Glycolysis is considered to be one of the earliest metabolic pathways to have evolved because it does not require oxygen, specialized structures or organelles, and is found in most organisms including prokaryotes and eukaryotes. It is a simple, efficient process that allows cells to derive energy from glucose and other sugars, making it an essential component of cellular metabolism. The production of ATP during glycolysis is much less than oxidative phosphorylation, but it still provides a significant amount of energy for cells. Thus, option B is the correct answer.

Question 16

Fatty acids usually have an even number of carbons in their structures. Catabolism of fatty acids produces two-carbon fragments that are converted to acetyl CoA molecules. What is the most likely way in which these acetyl CoA molecules would be metabolized in aerobic cellular respiration?
A) They would directly enter the electron transport chain.
B) They would directly enter the energy-yielding phase of glycolysis.
C) They would be converted to pyruvate and then undergo pyruvate oxidation upon transport into mitochondria.
D) They would directly enter the citric acid cycle.

Accepted Answer

Acetyl CoA molecules enter into the citric acid cycle in the mitochondria during aerobic cellular respiration. Here, carbon dioxide and ATP are produced through a series of reactions. Therefore, option D is the correct answer.

Question 17

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of ________.
A) competitive inhibition
B) allosteric regulation
C) the specificity of enzymes for their substrates
D) positive feedback regulation

Accepted Answer

This is an example of allosteric regulation, since the binding of citric acid at a different location from the active site changes the enzyme's shape and activity. It is not competitive inhibition, as the inhibitor (citric acid) is not competing with the substrate for binding to the active site. It is also not an example of the specificity of enzymes for their substrates or positive feedback regulation.

Question 18

A young dog has never had much energy. He is brought to a veterinarian for help, and she decides to conduct several diagnostic tests. She discovers that the dog's mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of the dog's condition?
A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
B) His cells cannot move NADH from glycolysis into the mitochondria.
C) His cells lack the enzyme in glycolysis that forms pyruvate.
D) His cells have a defective electron transport chain, so glucose is metabolized to lactate instead of to acetyl CoA.

Accepted Answer

The dog's mitochondria cannot use pyruvate for respiration because the transport protein needed to move pyruvate into the mitochondria is missing. This results in increased lactate production as pyruvate accumulates in the cytosol and is converted to lactate.

Question 19

The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. PFK is inhibited by high levels of which of the following molecules?
A) glucose and NAD⁺
B) AMP and ATP
C) ATP and citrate
D) citrate and CO₂

Accepted Answer

ATP and citrate are both high-energy molecules that indicate that the cell has sufficient energy stores and therefore does not need to proceed with glycolysis. When PFK is inhibited by ATP and citrate, glycolysis slows down, allowing the cell to conserve energy.

Question 20

Beta oxidation generates substrates for cellular respiration through which of the following processes?
A) catabolism of glucose
B) catabolism of glycogen
C) catabolism of proteins
D) catabolism of fatty acids

Accepted Answer

Beta oxidation is a metabolic process that breaks down fatty acids into acetyl-CoA, which can then be used in cellular respiration to generate ATP. Therefore, beta oxidation generates substrates for cellular respiration through the catabolism of fatty acids.

Quiz 9: Cellular Respiration and Fermentation

The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. About 10% of Springer spaniels suffer from canine PFK deficiency. Given its critical role in glycolysis, which of the following conditions would be a likely consequence for dogs afflicted with this disorder?

Which of the following metabolic processes normally occurs regardless of whether or not oxygen (O₂) is present?

A person on a strict diet and exercise regimen lost 7 kg (about 15 pounds) of body fat in just two weeks. What is the most likely way that the lost fat left the body?

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?

Even though plants cells carry out photosynthesis, they still use their mitochondria for oxidation of pyruvate. Under what conditions will plant cell mitochondria be active in this process?

In the absence of oxygen, yeast cells can obtain energy by fermentation, which results in the production of which of the following sets of molecules?

Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?

What kinds of cells carry out ATP synthesis by chemiosmosis?

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H⁺ → Lactate + NAD⁺

Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

Fatty acids usually have an even number of carbons in their structures. Catabolism of fatty acids produces two-carbon fragments that are converted to acetyl CoA molecules. What is the most likely way in which these acetyl CoA molecules would be metabolized in aerobic cellular respiration?

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of ________.

The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. PFK is inhibited by high levels of which of the following molecules?

Beta oxidation generates substrates for cellular respiration through which of the following processes?