Cellular Respiration

Question 1

Why is ATP often referred to as the "energy currency" of the cell?

Accepted Answer

It powers the majority of energy-requiring cellular reactions.

Question 2

Which specific bonds in the ATP molecule are considered "high-energy" phosphoanhydride bonds?

Accepted Answer

Bonds between the phosphate groups.

Question 3

What is the standard free energy change ($\Delta G$) for the hydrolysis of one mole of ATP?

Accepted Answer

-7.3 kcal/mole (-30.5 kJ/mol).

Question 4

In cellular metabolism, what is "energy coupling"?

Accepted Answer

Using an exergonic reaction to power an endergonic one.

Question 5

What is the process of transferring a phosphate group from ATP to another molecule called?

Accepted Answer

Phosphorylation.

Question 6

Where specifically within a cell does glycolysis take place?

Accepted Answer

The cytoplasm.

Question 7

What is the net yield of ATP and NADH from a single molecule of glucose during glycolysis?

Accepted Answer

2 ATP and 2 NADH.

Question 8

Why is glycolysis categorized as an anaerobic process?

Accepted Answer

It does not use oxygen directly.

Question 9

Which enzyme catalyzes the first step of glycolysis, effectively trapping glucose inside the cell?

Accepted Answer

Hexokinase.

Question 10

Which enzyme serves as the primary rate-limiting step in glycolysis?

Accepted Answer

Phosphofructokinase.

Question 11

What two 3-carbon molecules are the final products of glycolysis?

Accepted Answer

Pyruvate (or pyruvic acid).

Question 12

Before entering the citric acid cycle, pyruvate must be converted into which 2-carbon molecule?

Accepted Answer

Acetyl CoA.

Question 13

During the oxidation of pyruvate, what gas is released as a byproduct?

Accepted Answer

Carbon dioxide ($CO_2$).

Question 14

Where in a eukaryotic cell does the citric acid cycle (Krebs cycle) occur?

Accepted Answer

The mitochondrial matrix.

Question 15

The citric acid cycle begins when an acetyl group combines with which 4-carbon molecule?

Accepted Answer

Oxaloacetate.

Question 16

What are the total products of one turn of the citric acid cycle?

Accepted Answer

3 NADH, 1 $FADH_2$, 1 ATP/GTP, and 2 $CO_2$.

Question 17

Which electron carrier produced in the citric acid cycle is uniquely embedded in the inner mitochondrial membrane?

Accepted Answer

$FADH_2$ (via succinate dehydrogenase).

Question 18

Where are the protein complexes of the electron transport chain (ETC) located in eukaryotes?

Accepted Answer

Inner mitochondrial membrane.

Question 19

What is the final electron acceptor at the end of the electron transport chain?

Accepted Answer

Oxygen ($O_2$).

Question 20

To which complex in the electron transport chain does NADH deliver its electrons?

Accepted Answer

Complex I (NADH dehydrogenase).

Question 21

Why does $FADH_2$ result in the production of fewer ATP molecules than NADH?

Accepted Answer

It bypasses Complex I, pumping fewer protons.

Question 22

The electron transport chain pumps hydrogen ions into which specific compartment to create a gradient?

Accepted Answer

Mitochondrial intermembrane space.

Question 23

What is the name of the membrane-bound enzyme that uses a proton gradient to synthesize ATP?

Accepted Answer

ATP synthase.

Question 24

What percentage of the ATP generated from glucose catabolism is produced via oxidative phosphorylation?

Accepted Answer

Approximately 90 percent.

Question 25

If a cell has high levels of ATP, how is the activity of phosphofructokinase affected?

Accepted Answer

Enzyme activity decreases (feedback inhibition).