Aerobic Respiration

Question 1

Respiration

Answer 1

All living organisms carry out respiration

A catabolic, enzyme controlled reaction occurs inside cells to provide energy

Energy rich respiratory substrates, such as glucose or fatty acids, are broken down to release energy

High energy bonds are broken and lower energy bonds are formed

The excess energy released is used to phosphorylate ADP to form ATP or is released as heat energy

Question 2

For one molecule of glucose…

Answer 2

-The net yield of ATP from substrate level phosphorylation is 2 from glycolysis, 2 from Krebs

-2 reduced NAD from glycolysis - releasing 6 ATP

-2 reduced NAD from the link reaction - releasing 6 ATP

-6 reduced NAD from Krebs cycle - releasing 18 ATP

-2 reduced FAD from Krebs cycle - releasing 4 ATP

Question 3

Glycolysis
(in cytoplasm)

Answer 3

1. Glucose is phosphorylated using 2 ATP into hexose phosphate
2. The hexose phosphate splits into two triose phosphate molecules
3. The oxidation of these 2 triose phosphate molecules yield 2 ATP each by substrate level phosphorylation. Overall, glycolysis has a net gain of 2 ATP.
   Dehydrogenation releases 2 hydrogen that are picked up by NAD.
   The 2 pyruvate diffuse into the mitochondria.

Question 4

Link Reaction
(in mitochondrial matrix)

Answer 4

4. Oxidative decarboxylation of pyruvate catalysed by decarboxylase releases carbon dioxide
5. Dehydrogenation catalysed by dehydrogenase releases pairs of hydrogen atoms converting NAD to reduced NAD
6. The addition of coenzyme A forms acetyl CoA (2C) which enters the Krebs cycle

Question 5

Krebs cycle
(in mitochondrial matrix)

Answer 5

7. The acetate from acetyl CoA combines with a 4C compound to form a 6C compound
8. Decarboxylation forms a 5C compound and dehydrogenation occurs reducing NAD
9. Decarboxylation forms a 4C compound and dehydrogenation to reduce NAD.
   There is also substrate level phosphorylation giving 1 ATP
10. Dehydrogenation forming reduced FAD
11. Dehydrogenation forming reduced NAD

Question 6

Electron Transport Chain
(on inner mitochondrial membrane)

Answer 6

12. Reduced NAD and reduced FAD from glycolysis, link and Krebs reactions, deliver pairs of hydrogen atoms to the ETC
13. They are oxidised, delivering protons (H+) and high energy electrons (e-) to proton pumps on the inner mitochondrial membrane
14. Each reduced NAD utilises all 3 proton pumps, releasing 3 ATP.
    Each reduced FAD utilises only 2 proton pumps, releasing 2 ATP
15. Oxygen is the final acceptor in the electron transfer chain and is reduced to water

Question 7

Lipids

Answer 7

-Glycerol is converted into triose phosphate for use in glycolysis

-Fatty acids are split into 2C acetate fragments which feed into the Krebs cycle as acetyl CoA

Question 8

Proteins

Answer 8

-Amino acids are deaminated in the liver into ammonia and keto acids, one of which (pyruvate) is used in the link reaction while the others are fed into the Krebs cycle as intermediates