5A Aerobic Respiration

Question 1

Describe the link reaction

Answer 1

Converts pyruvate to Acetyl Coenzyme A

1. Pyruvate is decarboxylated (one carbon atom is removed from pyruvate in the form of CO2)
2. Pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD
3. Acetate is combined with Coenzyme A to form acetyl coenzyme A
4. No ATP is produced in this reaction

Question 2

How many times does the link reaction occur for every glucose molecule

Answer 2

Twice

Question 3

Describe stage 1 of the krebs cycle

Answer 3

Acetyl CoA from the link reaction combines with oxaloacetate to form a citrate molecule

Coenzyme A goes back to the link reaction to be used again

Question 4

Describe stage 2 of the krebs cycle

Answer 4

The 6C citrate molecule is converted to a 5C molecule

Decarboxylation occurs where CO2 is removed

Dehydrogenisation also occurs where hydrogen is removed

The hydrogen is used to produce reduced NAD from NAD

Question 5

Describe stage 3 of the krebs cycle

Answer 5

The 5C molecule is converted to a 4C molecule

Decarboxylation and dehydrogenation occur producing one molecule of reduced FAD and two of reduced NAD

ATP is produced by direct transfer of a phosphate group from an intermediate compound to ADP this is called substrate level phosphorylation

Citrate has now been converted into oxaloacetate

Question 6

Describe oxidative phosphorylation

Answer 6

the process where the energy carried by electrons from reduced coenzymes is used to make ATP.

It involves the electron transport chain and chemiosmosis

Hydrogen ions are released from Reduced NAD and Reduced FAD as they are oxidised to NAD and FAD
The H ions split into protons and electrons

The electrons move down the electron transport chain losing energy at each carrier

This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space

The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix - this forms an electrochemical gradient

Protons then move down the electrochemical gradient via ATP synthase this movement drives the synthesis of ATP from ADP and Pi

This is called chemiosmosis

In the mitochondrial matrix, at the end of the transport chain the protons, electrons and O2 from the blood combine to form water

Oxygen is said to be the electron accept

Question 7

How many ATP can be made from one glucose molecule

Answer 7

32

Question 8

What affects ATP production

Answer 8

Mitochondrial diseases

They affect the functioning of mitochondria and they affect how proteins involved in oxidative phosphorylation and the krebs cycle function reducing ATP production

This may cause anaerobic to increase causing lots of lactate to be produced which can cause cramp or diffuse into the bloodstream

Question 9

What else can be used in aerobic respiration

Answer 9

other respiratory substrates eg fatty acids, lipids and amino acids which can be converted into molecules that are able to enter the krebs cycle