Question 1

During cellular respiration, the cell harnesses the energy released from the combination of hydrogen and oxygen to form water. Which mechanism best explains how the cell prevents this reaction from occurring explosively and instead captures the energy for ATP synthesis?

Accepted Answer

By using a series of controlled redox reactions in the electron transport chain, gradually transferring electrons to oxygen.

Question 2

Which of the following correctly identifies the reduced and oxidized forms of NAD in cellular respiration?

Accepted Answer

NAD+ is the oxidized form; NADH is the reduced form.

Question 3

What class of molecules primarily make up the electron transport chain in mitochondria?

Accepted Answer

Proteins

Question 4

What is the role of oxygen in cellular respiration?

Accepted Answer

Oxygen is the final electron acceptor in the electron transport chain, allowing water to be formed.

Question 5

Match each stage of cellular respiration to its location in the cell:
A) Glycolysis
B) Citric Acid Cycle
C) Electron Transport Chain

Accepted Answer

A) Cytoplasm; B) Mitochondrial matrix; C) Inner mitochondrial membrane

Question 6

During glycolysis, one molecule of glucose ($C_6H_{12}O_6$) is converted into two molecules of pyruvate. Which of the following best describes the net products generated per glucose molecule in glycolysis?

Accepted Answer

2 ATP (net), 2 NADH, 2 pyruvate

Question 7

The intermediate step between glycolysis and the citric acid cycle involves the conversion of pyruvate to acetyl-CoA. For each glucose molecule, how many molecules of acetyl-CoA, NADH, and $CO_2$ are produced in this step?

Accepted Answer

2 acetyl-CoA, 2 NADH, 2 $CO_2$

Question 8

How many turns of the citric acid cycle occur per molecule of glucose, and what is the total output of NADH, FADH$_2$, and ATP (or GTP) from the cycle per glucose?

Accepted Answer

2 turns; 6 NADH, 2 FADH$_2$, 2 ATP

Question 9

Which statement best describes the orientation and location of the electron transport chain (ETC) in mitochondria?

Accepted Answer

The ETC is embedded in the inner mitochondrial membrane, with proteins oriented to pump H$^+$ ions into the intermembrane space.

Question 10

What is the role of ATP synthase in cellular respiration?

Accepted Answer

It synthesizes ATP from ADP and inorganic phosphate using the energy from the flow of H$^+$ ions down their concentration gradient.

Question 11

Why is oxygen essential for aerobic organisms in the process of cellular respiration?

Accepted Answer

Oxygen acts as the final electron acceptor in the electron transport chain, allowing the chain to continue and ATP to be produced.

Question 12

Calculate the total number of ATP molecules produced from one molecule of glucose during aerobic cellular respiration, accounting for all stages (glycolysis, intermediate step, citric acid cycle, and electron transport chain).

Accepted Answer

Approximately 38 ATP

Question 13

Which of the following molecules can enter the cellular respiration pathway at different points, and where do they enter?
A) Fatty acids
B) Amino acids
C) Glucose

Accepted Answer

A) Citric acid cycle as acetyl-CoA; B) Glycolysis or citric acid cycle depending on their structure; C) Glycolysis

Question 14

A patient is suffering from cyanide poisoning, which blocks the final step of the electron transport chain. What immediate effect does this have on cellular respiration?

Accepted Answer

ATP production via oxidative phosphorylation stops, leading to cell death.

Question 15

Which equation best represents the overall process of aerobic cellular respiration?

Accepted Answer

$C_6H_{12}O_6 + 6O_2 ightarrow 6CO_2 + 6H_2O + 	ext{energy (ATP)}$

Question 16

During the electron transport chain, what drives the active transport of H$^+$ ions across the inner mitochondrial membrane?

Accepted Answer

The downhill flow of electrons through protein complexes.

Question 17

If a cell is deprived of oxygen, which stage of cellular respiration is most directly affected first?

Accepted Answer

Electron transport chain

Question 18

Which of the following is a correct sequence of events in aerobic cellular respiration?

Accepted Answer

Glycolysis $\rightarrow$ Citric Acid Cycle $\rightarrow$ Electron Transport Chain

Question 19

Which molecule acts as the final electron acceptor in the electron transport chain, and what is the product formed?

Accepted Answer

O$_2$; H$_2$O

Cellular Respiration: Pathways, Mechanisms, and Molecular Components

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