Respiration

Question 1

Where does glycolysis occur

Answer 1

in the cytoplasm

Question 2

What happens in glycolysis
and what are the products

Answer 2

Glucose is phosphorylated twice to form glucose bisphosphate by the hydrolysis of 2 ATP molecules

Glucose bisphosphate is split into two TP molecules

The TP molecules are then oxidised by 2 NAD+ molecules to remove the phosphates to form Two Pyruvate molecules and 4 ATP

Products are :
2 x pyruvate
2 x NADH
net gain of 2 ATP

Question 3

Anaerobic respiration in plants/microbes and animals and what do they both produce

Answer 3

In plants/microbes
Pyruvate –> ethanol

In animals
Pyruvate –> lactate

both processes involve reforming NAD+ from oxidising NADH to be reused in glycolysis

Question 4

What happens in the link reaction

Answer 4

Pyruvate is actively transported into the mitochondrial matrix

Pyruvate is oxidised by NAD+ and decarboxylated to form acetate(2C), releasing carbon dioxide

Then Coenzyme A is added to acetate to from Acetyl CoA (2C)

Question 5

What happens in the Krebs cycle and where does it occur

Answer 5

CoA dissociates from Acetyl CoA to allow acetate to enter the Krebs cycle

Acetate combines with Oxaloacetate(4C) to form Citrate (6C)

Citrate is decarboxylated twice to form a 5C compound then a 4C compound , which release 2 molecules of CO2 and reduces 2NAD+ to 2NADH

The 4C compound is oxidised and ATP is produced by substrate level phosphorylation

The 4C compound is oxidised again to reduce FAD to FADH2

The 4C is used to regenerate Oxaloacetate reducing NAD+ to NADH

This cycle occurs twice per glucose molecule

occurs in the matrix

Question 6

What are the products of the Krebs cycle per molecule of glucose

Answer 6

2 ATP
6 NADH
2 FADH2
4 CO2

Question 7

How can lipids and amino acids be used instead of glucose in respiration

Answer 7

lipids are hydrolysed and the glycerol is phosphorylated into TP and can enter the link reaction and Krebs cycle

Amino acids are hydrolysed and the amino group is removed ( Deamination )

the carbon compound that is left can enter the link reaction and then the Krebs cycle

Question 8

What happens in oxidative phosphorylation and where does it occur

Answer 8

It occurs in the inner mitochondrial membrane

The NADH and FADH2 molecules from the Krebs cycle and glycolysis are oxidised to release protons and electrons

The electrons released will pass down an electron transport chain, which release energy that is used to transport the protons across the membrane

this creates an electrochemical gradient across the membrane

the protons will then diffuse back across through an ATP synthase enzyme, causing ATP to be synthesised from ADP and Pi

Oxygen is the terminal electron acceptor and will combine with electrons that have passed through the electron transport chain, forming water as combines with protons also

Question 9

Net gain of ATP in aerobic respiration

Answer 9

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