5.2 RESPIRATION

Question 1

What are the stages of aerobic respiration?

Answer 1

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Oxidative phosphorylation

Question 2

Where does glycolysis occur?

Answer 2

In the cytoplasm of a cell.

Question 3

Outline glycolysis.

Answer 3

1. Glucose is phosphorylated using 2ATP molecules that provide 2 Pi.
2. The phosphorylated glucose splits into 2 x 3C chains of triose phosphate.
3. PER TRIOSE PHOSPHATE: NAD takes electrons to form reduced NAD (NADH + H⁺). 2ATP molecules formed from the removal of Pi from the triose phosphate.
4. Left with two 3C chains called pyruvate.

Question 4

What is the yield per glucose molecule during glycolysis?

Answer 4

• 2 ATP (4 made - 2 used)
• 2 NADH
• 2 pyruvate

Question 5

Where does the links cycle occur?

Answer 5

In the mitochondria.

Question 6

Outline the Links cycle. (per TP)

Answer 6

1. Gets oxidised and converts NAD to NADH + H⁺.
2. Loses carbon dioxide in decarboxylation.
3. Left with a 2C: acetate.
4. Acetate joins with Coenzyme A to form acetyl CoA.

Question 7

What is the yield per glucose molecule during the Links cycle?

Answer 7

• 2 carbon dioxides
• 2 NADH + H⁺
• 2 acetyl CoA

Question 8

Where does the Krebs cycle occur?

Answer 8

In the mitochondria

Question 9

Outline the Krebs cycle. (per acetyl CoA)

Answer 9

1. Acetyl CoA reacts with a 4C molecule to form a 6C molecule.
2. 6C undergoes decarboxylation (loses CO2) and NAD is reduced to NADH + H⁺, leaving a 5C molecule.
3. 5C undergoes decarboxylation (loses CO2) and NAD is reduced to NADH + H⁺, leaving a 4C molecule.
4. GTP occurs where ATP is produced.
5. 4C is oxidised again to convert NAD to NADH + H⁺, and FAD to FADH + H⁺, leaving a 4C molecule.
6. The 4C is then reused in the Kreb cycle.

Question 10

What is the yield per glucose molecule during the Krebs cycle?

Answer 10

• 2 ATP
• 6 NADH + H⁺
• 2 FADH + H⁺
• 4 Carbon dioxide

Question 11

Outline oxidative phosphorylation.

Answer 11

1. Coenzymes carry electrons to the ETCs.
2. These electrons travel down the ETCs ina. series of REDOX reactions.
3. As electrons go down the chain, they release energy so H⁺ protons can be actively transported across the membrane into the inner membrane space.
4. Protons buildup in this space until there is a chemiosmotic gradient.
5. Then the H⁺ protons will diffuse back into the stroma through ATP synthase channels, which make ATP.
6. In the matrix, oxygen joins with the H⁺ protons and electrons at the end of the ETC to form water.

OXYGEN IS THE FINAL ACCEPTOR OF PROTONS & ELECTRONS.

Question 12

What is the only thing that can occur in anaerobic respiration?

Answer 12

Glycolysis

Question 13

Why can the other process not occur in a lack of oxygen?

Answer 13

Oxygen is the final acceptor of electrons and protons, so without oxygen, there would be a buildup of these things. Then NADH and FADH can’t release electrons and regenerate NAD/FAD so the process stops.

Question 14

What happens in the anaerobic respiration of plants?

Answer 14

Pyruvate + NADH = Ethanol + ATP + NAD

Question 15

What happens in the anaerobic respiration of animals?

Answer 15

Pyruvate + NADH = Lactate + NAD + ATP