4.2: Cellular respiration & Redox reactions

Question 1

What is cellular respiration?

Answer 1

Series of chemical reactions that convert the chemical energy in fuel molecules into chemical energy of ATP.

Question 2

Aerobic vs Anaerobic respiration

Answer 2

Aerobic: In the presence of oxygen
Anaerobic: In the absence of oxygen

Question 3

How fast is energy released during cellular respiration? Why?

Answer 3

Slowly. Gradually released in a series of reactions so the stored energy doesn’t get released all at once as heat.

Question 4

Substrate-level phosphorylation (% of ATP production)

Answer 4

One of the two ways to produce ATP. Single enzyme transfers a phosphate group from an organic molecule directly to ADP. Only about 12%.

Question 5

Oxidative phosphorylation (% of ATP production)

Answer 5

One of the two ways to produce ATP. Chemical energy from organic molecules are first transferred to electron carriers, which carry energy to the electron transport chain. This chain transfers energy to a final electron acceptor, and during that ATP is produced. 88% of ATP production.

Question 6

What is an oxidation-reduction reaction?

Answer 6

Redox for short. Chemical reactions in which electrons are transferred from one molecule to another. Oxidation, “loss of e-“ and reduction, “gain of e-“.

Question 7

2 important electron carriers? Their forms?

Answer 7

Nicotinamide adenine dinucleotide - Oxidized form (NAD+), Reduced form (NADH).
Flavin adenine dinucleotide - Oxidized form (FAD), Reduced form (FADH2).

Question 8

What accompanies electron movement during redox reactions of organic molecules? (such as NAD+ or FAD)

Answer 8

Gain or loss of e- = Gain or loss of protons (H+). This means reduced molecules have an increase in C-H bonds while oxidized molecules have a decrease in C-H bonds.

Question 9

Stage 1 of cellular respiration

Answer 9

Glycolysis: Glucose is partially broken down to produce pyruvate, and energy is transferred to ATP & reduced electron carriers.

Question 10

Stage 2 of cellular respiration

Answer 10

Pyruvate is oxidized to acetyl-coenzyme A (acetyl-CoA), producing reduced electron carriers and releasing CO2.

Question 11

Stage 3 of cellular respiration

Answer 11

Citric acid cycle: Acetyl group is completely oxidized to CO2 and transfers nearly twice as much energy to ATP & reduced electron carriers than that of stages 1 and 2 combined.

Question 12

Stage 4 of cellular respiration

Answer 12

Oxidative phosphorylation: Reduced electron carriers donate electrons to the electron transport chain producing large amount of ATP.

Question 13

Location of cellular respiration (Eukaryotes vs Prokaryotes)

Answer 13

Eukaryotes: Glycolysis (stage 1) in cytoplasm. 3 other stages all in mitochondria. Electron transport chain in mitochondrial membrane.
Prokaryotes: All reactions take place in cytoplasm. Electron transport chain in plasma membrane.