Y2: Respiration

Question 1

What are the four stages on aerobic respiration and where do they take place?

Answer 1

1. Glycolysis (cytoplasm)
2. Link reaction (Mitochondrial matrix)
3. Krebs cycle (Mitochondrial matrix)
4. Oxidative Phosphorylation (Cristae)

Question 2

Glycolysis process? 3 stages?

Answer 2

1. Substrate level phosphorylation - The glucose has two phosphate groups added to it from two ATP molecules.
2. Phosphorylation makes the glucose-2-phosphate unstable and it splits into two 3-carbon compounds, triose phosphate (TP).
3. The two TP molecules are both oxidised to form two pyruvate molecules by removing a hydrogen from each. The hydrogen is picked up by two NAD molecules to become NADH.

Question 3

Net products from glycolysis?

Answer 3

2 ATP, 2 NADH, 2 Pyruvate

Question 4

What is the link reaction?

Answer 4

This reaction occurs in the mitochondrial matrix and converts pyruvate into acetyl CoA.

Question 5

Link reaction process? 1, 2 & 3?

Answer 5

Pyruvate is decarboxylated into acetyl CoA-contains two carbons, so a carbon is removed in this stage in the form of carbon dioxide.

2 hydrogen atoms are also removed to oxidise the carbon compound further to create acetate. This is known as dehydrogenation and is catalysed by dehydrogenase enzymes.

The NAD picks up the hydrogen to become NADH. The coenzyme CoA combines with the acetate that is formed to create acetyl CoA, this is to assist in acetyl reacting in the Krebs cycle.

Question 6

Net products of link reaction?

Answer 6

2 x Acetyl CoA
2 CO2
2 reduced NAD

Question 7

How many times does the link reaction take place per glucose molecule?

Answer 7

2

Question 8

Krebs cycle?

Answer 8

The acetyl CoA reacts with a four-carbon molecule, releasing coenzyme A and producing a six-carbon molecule that enters the Krebs cycle.

In a series of oxidation-reduction reactions, the Krebs cycle generates 5 carbon molecule then 4 carbon molecule which is oxidised to another 4 carbon molecule

CO2 are lost in the decarboxylation

Question 9

Net products from Krebs cycle?

Answer 9

2 ATP
6 NADH
2FADH
4 CO2

Question 10

How many times does Krebs cycle happen per glucose molecule?

Answer 10

2

Question 11

What is the purpose of oxidative phosphorylation?

Answer 11

To synthesise ATP from the remaining NADH and FADH

Question 12

Process of oxidative phosphorylation? 7 steps? oxygen?

Answer 12

1. At proton pump A NADH is oxidised into NAD+ donating 2 high energy e- to the proton pump
2. Proton pump A uses energy to actively transport H+ ions from mitochondrial matrix to the inter-membranal space
3. The electrons enter the electron transport chain
4. At proton pump B FADH is oxidised and more protons are pumped, same at proton pump C
5. This generates and maintains a chemiosmotic gradient
6. The H+ ions travel through ATP synthase down the chemiosmotic gradient catalysing formation of ATP
7. Oxygen acts as the final electron acceptor forming water from 1/2 oxygen, 2H+ ions and 2 e-

Question 13

Anaerobic respiration in plants and yeast?

Products?

Answer 13

The pyruvate produced in glycolysis is reduced to form ethanol (in plants and microbes) by gaining the hydrogen from reduced NAD.

This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

products: ethanol, NAD, CO2

Question 14

Anaerobic respiration in animals?

Products?

Answer 14

The pyruvate produced in glycolysis is reduced to form lactate (in animals) by gaining the hydrogen from reduced NAD.

This oxidises NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced.

Products: lactate, NAD

Question 15

What happens to the lactate in anaerobic respiration?

2 Options?

Answer 15

Lactate is oxidised back into pyruvate

or

Transported to the liver and converted into glycogen