Respiration

Question 1

Glycolysis

Answer 1

First stage of respiration for both aerobic + anerobic respiration. Does not require oxygen, so it is an anaerobic process.

Question 2

Where does glycolysis happen?

Answer 2

Cell Cytoplasm

Question 3

Glycolysis Process

Answer 3

1. Glucose phosphorylated by 2 x ATP to form glucose phosphate
2. Glucose phosphate splits into 2 x triosphosphate
3. 2 x triose phosphate oxidised to 2 x pyruvate. Hydrogen removed from each triose phosphate molecule and added to co-enzyme NAD, forming 2 reduced NAD
4. 4 ATP regenerated. 2 ATP used. Net gain of ATP = 2 ATP

Question 4

Products of Glycolysis

Answer 4

1. 2 x Pyruvate (actively transported into mitochondrial matrix, used in link reaction)
2. 2 x reduced NAD (used in oxidative phosphorylation)
3. 2 x ATP

Question 5

Anaerobic Respiration

Answer 5

1. Glycolysis occurs and 2 x pyruvate are produced, and 2 x reduced NAD and 2 x ATP
2. During anaerobic respiration, where there is no oxygen, in animals + bacteria, pyruvate is converted to lactate and in plants and yeast, it is converted to ethanol
3. This causes oxidation of reduced NAD, NAD regenerated
4. NAD is required for glycolysis to occur, therefore, glycolysis can continue
5. Anaerobic respiration less efficient than aerobic respiration. Less ATP produced. Most ATP produced in oxidative phosphorylation

Question 6

Link Reaction

Answer 6

1. Second stage of aerobic respiration
2. Occurs in matrix of mitochondria (pyruvate actively transported from cell cytoplasm to matrix of mitochondria)
3. Pyruvate is oxidised + decarboxylated to form acetate. The hydrogen is used to reduce co enzyme NAD, forming reduced NAD and a CO2 is released
4. Acetate combines / reacts with Co-enzyme A forming acetyl coenzyme A

Products of one link reaction (called link reaction because it links glycolysis to Krebs cycle)

1. 1 x CO2 (waste product)
2. 1 x Reduced NAD (to be used in oxidative phosphorylation)
3. 1 x coenzyme A (to be used in Krebs cycle)

Question 7

Krebs Cycle

Answer 7

1. Occurs in matrix of mitochondria
2. Acetyl coenzyme A (2C) reacts / combines with 4 C molecule oxaloacetate, to form 6C molecule, called citrate
3. Coenzyme A released + returns to link reaction to be reused in next link reaction
4. 6C molecule now converted to 5C molecule. It is decarboxylated and dehydrogenated. CO2 released and the hydrogen is used to reduce coenzyme NAD to reduced NAD
5. Oxaloacetate is now regenerated so it can be reused in next krebs cycle. The 5C molecule converted back to 4C molecule by a series of redox reactions:

• Decarboxylation of 5C molecule. CO2 released
• Dehydrogenation. Hydrogen used to reduce 2 NAD to 2 reduced NAD and FAD to reduced FAD
• Substrate level phosphorylation to form ATP: This is where Pi (phosphate group) is directly transferred from intermediate compound to ADP to form ATP molecule

Products of 1 Krebs cycle:

1 x Coenzyme A - reused in next link reaction
1 x oxaloacetate - reused in next krebs cycle
2 x CO2 - waste product
1 x ATP - provides energy
3 x reduced NAD - used in oxidative phosphorylation
1 x reduced FAD - used in oxidative phosphorylation