Question 1

Which of the following best describes the overall flow of energy in an ecosystem as depicted in the first image?

Accepted Answer

Energy enters as sunlight, is converted to chemical energy by chloroplasts, used by mitochondria, and eventually lost as heat.

Question 2

In the reaction $$\mathrm{C_6H_{12}O_6$ + 6\ O_2$ ightarrow 6\ CO_2$ + 6\ H_2O + 	ext{Energy}}$$, which molecule is oxidized and which is reduced?

Accepted Answer

Glucose is oxidized; oxygen is reduced.

Question 3

Which of the following statements about redox reactions is correct?

Accepted Answer

The substance that loses electrons is oxidized, and the substance that gains electrons is reduced.

Question 4

In the sodium and chlorine reaction $$\mathrm{Na + Cl \rightarrow Na^+ + Cl^-}$$, which element acts as the oxidizing agent?

Accepted Answer

Chlorine

Question 5

During glycolysis, what is the net gain of ATP and NADH per molecule of glucose?

Accepted Answer

$$2$$ ATP and $$2$$ NADH

Question 6

Which process in cellular respiration produces the most ATP?

Accepted Answer

Oxidative phosphorylation

Question 7

What is the primary role of oxygen in cellular respiration?

Accepted Answer

It acts as the final electron acceptor in the electron transport chain.

Question 8

Which of the following best explains why fats produce more ATP per gram than carbohydrates?

Accepted Answer

Fats have more hydrogen atoms, providing more high-energy electrons for the electron transport chain.

Question 9

Which enzyme is a key regulatory point in glycolysis and is inhibited by high levels of ATP?

Accepted Answer

Phosphofructokinase

Question 10

A patient’s muscle cells are producing large amounts of lactate. Which condition is most likely occurring?

Accepted Answer

The patient’s muscle cells are undergoing fermentation due to low oxygen availability.

Question 11

Which of the following is a correct description of substrate-level phosphorylation?

Accepted Answer

A phosphate group is directly transferred from a substrate to ADP, forming ATP.

Question 12

Which of the following is NOT a product of the citric acid cycle for each acetyl CoA that enters?

Accepted Answer

FAD

Question 13

Why does the electron transport chain in mitochondria consist of multiple protein complexes instead of a single step?

Accepted Answer

To release energy in small, manageable amounts for ATP synthesis.

Question 14

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation regenerates NAD+ so glycolysis can continue in the absence of oxygen.

Question 15

Which of the following is a facultative anaerobe?

Accepted Answer

Yeast

Question 16

What is the main reason the actual ATP yield from cellular respiration is often less than the theoretical maximum of 32 ATP per glucose?

Accepted Answer

Some energy from the proton-motive force is used for other cellular work.

Question 17

Which of the following best explains the evolutionary significance of glycolysis?

Accepted Answer

It is an ancient pathway that does not require oxygen or membrane-bound organelles.

Question 18

Which of the following molecules is the final electron acceptor in aerobic cellular respiration?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 19

Which of the following is a correct comparison between aerobic respiration and fermentation?

Accepted Answer

Aerobic respiration produces much more ATP per glucose than fermentation.

Question 20

Which of the following best describes the role of NAD+ in cellular respiration?

Accepted Answer

It acts as an electron carrier, accepting electrons during redox reactions.

Cellular Respiration: Pathways for Energy Harvesting

Study Guide - Practice Questions