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An athlete performs high-intensity sprints for 30 seconds. What happens to glucose metabolism in their muscle cells during the sprint?
A) Cellular respiration continues normally
B) Glycolysis increases and fermentation takes over
C) Fatty acids are used as the main fuel source
D) The electron transport chain speeds up
Answer: B
Rationale: During intense exercise, oxygen supply is insufficient, and muscle cells rely on glycolysis and fermentation to quickly produce ATP
A patient with a respiratory illness has low oxygen levels. How do their cells continue to produce ATP without oxygen?
A) Citric acid cycle speeds up
B) Fermentation begins producing ATP and lactate
C) Oxidative phosphorylation increases ATP output
D) Pyruvate enters the citric acid cycle directly
answer: B
Rationale: Without sufficient oxygen, the cells undergo fermentation, converting pyruvate into lactate to regenerate NAD+ and continue glycolysis.
A person has a mutation that causes malformation of the inner mitochondrial membrane. What is the effect on ATP production?
A) ATP production increases
B) Glycolysis stops
C) Oxidative phosphorylation is disrupted
D) Pyruvate cannot be produced
Answer: C
Rationale: The inner mitochondrial membrane houses the electron transport chain and ATP synthase. A defect in the membrane would disrupt ATP production through oxidative phosphorylation.
A drug inhibits the enzyme phosphofructokinase (PFK). How does this affect glycolysis?
A) Glycolysis speeds up
B) Glycolysis stops
C) The citric acid cycle compensates
D) NADH production increases
Answer: B
Rationale: Phosphofructokinase (PFK) is a key regulatory enzyme in glycolysis. Inhibiting it stops glycolysis at an early stage.
During intense exercise, muscle cells become anaerobic. How are energy requirements met?
A) The citric acid cycle increases activity
B) Fermentation produces lactate and a small amount of ATP
C) Fats are broken down to produce ATP
D) The electron transport chain works faster
Answer: B
Rationale: In anaerobic conditions, fermentation occurs to produce ATP and lactate, allowing glycolysis to continue in the absence of oxygen.
In cases of prolonged starvation, the body uses fats and amino acids for energy. How do these molecules enter the respiration pathway?
A) They enter directly into the electron transport chain
B) Fats and amino acids are converted into glucose
C) They are broken down into molecules that enter the citric acid cycle
D) Fats produce pyruvate while amino acids produce NADH
Answer: C
Rationale: Fats are broken down into acetyl-CoA, which enters the citric acid cycle, and amino acids are deaminated and then enter various stages of the cycle
A person’s cells are unable to complete the citric acid cycle. What happens to NADH production?
A) NADH production increases
B) NADH production stops
C) Glycolysis compensates for NADH production
D) Pyruvate replaces NADH in the cycle
Answer: B
Rationale: NADH is mainly produced in the citric acid cycle, so if the cycle is disrupted, NADH production halts.
In patients suffering from chronic hypoxia, how is energy derived from glucose?
A) ATP is produced primarily by fermentation
B) The citric acid cycle increases efficiency
C) The electron transport chain compensates for the lack of oxygen
D) Glycolysis stops entirely
Answer: A
Rationale: In low oxygen conditions, cells rely on anaerobic processes like glycolysis and fermentation to produce ATP.
After sprinting, lactic acid builds up in a runner's muscle cells. What causes this buildup?
A) Increased citric acid cycle activity
B) Incomplete breakdown of glucose during fermentation
C) Glycolysis speeds up and the electron transport chain slows down
D) Overproduction of pyruvate
Answer: B
Rationale: In anaerobic conditions, pyruvate is converted into lactate, leading to lactic acid buildup.
After a heart attack, some heart muscle cells die due to lack of oxygen. Why does oxygen deprivation lead to cell death?
A) Cells switch to glycolysis, which is insufficient
B) The citric acid cycle speeds up too much
C) NADH builds up in the cytosol
D) Without oxygen, the electron transport chain and ATP production stop
Answer: D
Rationale: Oxygen is required for the electron transport chain. Without it, ATP production halts, leading to cell death.
After consuming a large carbohydrate-heavy meal, how is the excess glucose processed?
A) It is immediately used for energy via glycolysis
B) It is stored as glycogen or fat after glycolysis and respiration
C) It enters the citric acid cycle directly
D) The glucose is stored in mitochondria for later use
Answer: B
Rationale: Excess glucose is first broken down via glycolysis and respiration. If not needed for immediate energy, it is stored as glycogen or fat.
A genetic disorder impairs the function of dehydrogenase enzymes. How does this affect ATP production?
A) NADH is not produced, halting oxidative phosphorylation
B) Glycolysis compensates by increasing ATP output
C) ATP production increases due to increased fermentation
D) Pyruvate bypasses the citric acid cycle
Answer: A
Rationale: Dehydrogenase enzymes are necessary for transferring electrons to NAD+, producing NADH. If this is impaired, the electron transport chain and ATP production halt.
After intense exercise, how is lactate recycled?
A) Lactate is broken down directly in the muscles
B) Lactate is transported to the liver and converted back to glucose
C) Lactate is used to produce ATP directly in the mitochondria
D) Lactate is converted into pyruvate within the muscles
Answer: B
Rationale: After exercise, lactate is transported to the liver via the blood, where it is converted back into glucose.
n high-altitude environments, how does the body adapt to meet energy demands?
A) Glycolysis is inhibited
B) Fermentation becomes the primary ATP source
C) The body increases the efficiency of oxygen utilization in cellular respiration
D) Mitochondria increase their ATP output
Answer: C
Rationale: In low-oxygen environments, the body adapts by improving the efficiency of oxygen delivery and utilization in cells.
A drug causes a deficiency in NAD+ availability. How does this impact ATP production?
A) Glycolysis speeds up
B) NADH production increases
C) Glycolysis and the citric acid cycle slow down, reducing ATP production
D) Pyruvate production increases
Answer: C
Rationale: NAD+ is essential for glycolysis and the citric acid cycle. A lack of NAD+ would slow these processes, reducing ATP production.
What is the chemical equation for aerobic cellular respiration?
A) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP
B) 6 CO2 + 6 H2O → C6H12O6 + O2
C) C6H12O6 + ADP → CO2 + ATP
D) C6H12O6 → O2 + ATP + CO2
Answer: A
Rationale: The correct equation is glucose (C6H12O6) reacting with oxygen to produce carbon dioxide, water, and ATP.
What is the role of dehydrogenase enzymes in cellular respiration?
A) They split glucose into two pyruvates
B) They remove hydrogen atoms from molecules, transferring electrons to NAD+ and FAD
C) They add phosphates to ADP to form ATP
D) They transport oxygen to the mitochondria
Answer: B
Rationale: Dehydrogenases transfer hydrogen atoms (electrons) to NAD+ and FAD, which are used in ATP production.
What is the function of NAD+ and NADH in aerobic respiration?
A) NAD+ stores electrons and transfers them to the electron transport chain
B) NADH breaks down glucose molecules
C) NADH captures sunlight for photosynthesis
D) NAD+ and NADH are enzymes that produce ATP
Answer: A
Rationale: NAD+ accepts electrons during glycolysis and the citric acid cycle to form NADH, which transfers electrons to the electron transport chain.
Which of the following lists the correct order of the stages of cellular respiration?
A) Glycolysis → Citric acid cycle → Oxidative phosphorylation
B) Glycolysis → Oxidative phosphorylation → Citric acid cycle
C) Oxidative phosphorylation → Glycolysis → Citric acid cycle
D) Citric acid cycle → Glycolysis → Oxidative phosphorylation
Answer: A
Rationale: Glycolysis occurs first, followed by the citric acid cycle (Krebs cycle), and then oxidative phosphorylation.
What is the importance of the inner mitochondrial membrane in ATP production?
A) It is where glycolysis takes place
B) It contains enzymes for the citric acid cycle
C) It provides the surface for the electron transport chain and ATP synthase
D) It allows glucose to enter the mitochondria
Answer: C
Rationale: The inner membrane houses the electron transport chain and ATP synthase, crucial for ATP production.
What happens during the energy investment phase of glycolysis?
A) Glucose is broken into two pyruvate molecules
B) Glucose is split and ATP is consumed to prepare for energy payoff
C) ATP and NADH are produced
D) Pyruvate is converted into acetyl-CoA
Answer: B
Rationale: In the energy investment phase, ATP is used to split glucose into two molecules of G3P, which leads to ATP production in later steps.
How is the concentration gradient of glucose maintained in cells during glycolysis?
A) ATP powers the movement of glucose into the cell
B) The cell uses fermentation to convert glucose into pyruvate
C) The cell immediately breaks down glucose, preventing buildup
D) Glucose is stored in the mitochondria for later use
Answer: C
Rationale: Cells constantly metabolize glucose, preventing a concentration buildup and maintaining the gradient for more glucose to enter.
What happens during the energy payoff phase of glycolysis?
A) ATP is used to convert glucose into pyruvate
B) ATP and NADH are produced as pyruvate is formed
C) The citric acid cycle is initiated
D) Oxygen is consumed to break down glucose
Answer: B
Rationale: During the energy payoff phase, two molecules of ATP and NADH are produced, and pyruvate is formed.
Why is glycolysis able to occur in the absence of oxygen?
A) It does not require oxygen to produce ATP
B) Oxygen is consumed in the first step
C) The citric acid cycle produces oxygen
D) NADH donates electrons directly to pyruvate
Answer: A
Rationale: Glycolysis does not require oxygen and can produce ATP anaerobically through fermentation if necessary.
What happens to pyruvate if oxygen is not present?
A) Pyruvate is converted into lactate or ethanol
B) Pyruvate enters the citric acid cycle
C) Pyruvate generates ATP through oxidative phosphorylation
D) Pyruvate is stored in the mitochondria
Answer: A
Rationale: In the absence of oxygen, pyruvate undergoes fermentation, producing lactate (in animals) or ethanol (in yeast).
How does fermentation help sustain glycolysis?
A) It provides extra ATP
B) It regenerates NAD+ needed for glycolysis
C) It produces glucose for glycolysis
D) It produces oxygen to help break down pyruvate
Answer: B
Rationale: Fermentation regenerates NAD+, which is required for glycolysis to continue in anaerobic conditions.
What is the difference in ATP production between cellular respiration and fermentation?
A) Cellular respiration produces more ATP per glucose molecule
B) Fermentation produces more ATP than cellular respiration
C) Fermentation produces oxygen, which boosts ATP production
D) Cellular respiration produces the same amount of ATP as fermentation
Answer: A
Rationale: Cellular respiration produces around 36-38 ATP per glucose molecule, while fermentation produces only 2 ATP.
Why can’t human cells rely solely on glycolysis for long-term energy needs?
A) It produces toxic byproducts
B) It generates too little ATP to meet energy demands
C) It requires oxygen to function
D) It produces excessive NADH
Answer: B
Rationale: Glycolysis produces only 2 ATP per glucose, which is insufficient for long-term energy requirements, especially in high-energy-demand cells.
What is the function of the electron transport chain in oxidative phosphorylation?
A) It produces glucose from pyruvate
B) It transports protons and uses them to generate ATP
C) It directly splits glucose into pyruvate
D) It transfers electrons to produce NADH
Answer: B
Rationale: The electron transport chain pumps protons across the inner mitochondrial membrane, generating a proton gradient used by ATP synthase to produce ATP.
How does chemiosmosis contribute to ATP synthesis?
A) It breaks down glucose into pyruvate
B) It uses the proton gradient created by the electron transport chain to power ATP synthase
C) It produces glucose from fatty acids
D) It transfers electrons from NADH to oxygen
Answer: B
Rationale: Chemiosmosis refers to the movement of protons back into the mitochondrial matrix through ATP synthase, driving ATP production.
What happens to pyruvate if oxygen is available?
A) It is converted into lactate
B) It enters the citric acid cycle as acetyl-CoA
C) It is used to produce NADH directly
D) It forms glucose in the mitochondria
Answer: B
Rationale: In the presence of oxygen, pyruvate is converted into acetyl-CoA, which enters the citric acid cycle for further breakdown.
Compare the energy yield from glycolysis to the total energy yield from one glucose molecule in aerobic respiration.
A) Glycolysis produces more energy than the electron transport chain
B) Aerobic respiration yields far more ATP than glycolysis alone
C) Both glycolysis and respiration produce equal amounts of ATP
D) Glycolysis is the most efficient stage of respiration
Answer: B
Rationale: Glycolysis produces 2 ATP per glucose molecule, while the entire aerobic respiration process produces 36-38 ATP.
How do fats and amino acids enter the aerobic respiration pathway?
A) They are converted into pyruvate and enter glycolysis
B) They are broken down into acetyl-CoA and enter the citric acid cycle
C) They bypass the citric acid cycle and enter the electron transport chain
D) They directly produce NADH
Answer: B
Rationale: Fats and amino acids are broken down into acetyl-CoA, which enters the citric acid cycle for ATP production.
Why is lactate transported to the liver after fermentation occurs in muscle cells?
A) To be converted into pyruvate for further ATP production
B) To be stored as fat
C) To produce more ATP in the liver
D) To be converted back into glucose
Answer: D
Rationale: Lactate is transported to the liver to be converted back into glucose, which can then be reused for energy.
What is the significance of the citric acid cycle in terms of NADH and FADH2 production?
A) It produces glucose and oxygen for respiration
B) It provides electrons for the electron transport chain by producing NADH and FADH2
C) It directly produces large amounts of ATP
D) It stores NAD+ for glycolysis
Answer: B
Rationale: The citric acid cycle generates NADH and FADH2, which carry electrons to the electron transport chain for ATP production.
