Respiration

Question 1

ATP Production

Answer 1

1. H atoms dissociate from NADH and FADH2, and are split to form H+ and electrons
2. Electrons are passed down the ETC, comprising of a series of electron carriers of progressively lower energy levels to the final electron acceptor, oxygen, via redox
3. Energy released during the transfer is used to pump H+ via active transport from the mitochondrial matrix, across the inner mitochondrial membrane, into the intermembrane space
4. Since the intermembrane space is impermeable to H+, accumulation of H+ sets up an electrochemical and proton gradient between the intermembrane space and mitochondrial matrix for ATP synthesis
5. H+ diffuses down the proton gradient from the intermembrane space, back to the mitochondrial matrix through ATP synthase, releasing electrical potential energy, driving phosphorylation of ADP to ATP, catalysed by ATP synthase

Question 2

Function of oxygen OR Water formation

Answer 2

1. Oxygen is the final electron acceptor at the end of the electron transport chain, and combines with H+ and electrons to form water, catalysed by cytochrome oxidase
2. Electrons are accepted by oxygen, thus electron carriers along the ETC are oxidised, enabling continued NAD and FAD regeneration
3. This maintains electron flow along the ETC and the built up of proton gradient between the intermembrane space and mitochondrial matrix for ATP synthesis by chemiosmosis

Question 3

Why lesser glucose OR lesser yield of ATP

Answer 3

1. During aerobic respiration, for every glucose molecule broken down and oxidised, 2 ATP is formed each during glycolysis and Krebs Cycle, and 34 ATP is formed during oxidative phosphorylation, giving a total of 38 ATP
2. During anaerobic respiration, for every glucose molecule broken down and oxidised, 2 ATP is formed during glycolysis
3. This means that 19 times less glucose is needed during aerobic conditions compared to anaerobic conditions, to produce the same number of ATP for cell metabolism

Question 4

Role of ETC

Answer 4

1. High energy electrons are transferred from NADH and FADH2 formed during glycolysis, link reaction, krebs cycle to oxygen via electron carriers of the ETC
2. Energy released during the transfer is used to pump H+ via active transport from the mitochondrial matrix, across the inner mitochondrial membrane into the intermembrane space
3. Resulting in the built up of a proton gradient between the mitochondrial matrix and the intermembrane space for ATP synthesis by chemiosmosis
4. NAD and FAD are regenerate for reuse in glycolysis, link reaction and Krebs cycle

Question 5

Role of NAD and FAD

Answer 5

1. Acts as a hydrogen atom carrier and coenzyme for dehydrogenase
2. Hydrogen atom is transferred to NAD and FAD, reducing NAD and FAD to NADH and FADH2 respectively.
3. NADH and FADH2 carries hydrogen atoms to the inner mitochondrial membrane for oxidative phosphorylation to occur, oxidising NADH and FADH2 to NAD and FAD respectively.
4. NAD and FAD is regenerated for subsequent glycolysis, link reaction, krebs cycle and oxidative phosphorylation

Question 6

Significance of the conversion of pyruvate to lactate

lactate -> lactic acid -> muscle

Answer 6

1. Lactate fermentation regenerates NAD from NADH for glycolysis to continue
2. It allows for production of some ATP via substrate level phosphorylation for intense muscle activity, even when oxygen is not available as the final electron acceptor

Question 7

Significance of the conversion of pyruvate to ethanol

Answer 7

1. Alcoholic fermentation regenerates NAD from NADH for glycolysis to continue
2. It allows for production of some ATP via substrate level phosphorylation for metabolic activity, even when oxygen is not available as the final electron acceptor