EN: Respiration and Anaerobic Respiration

Question 1

What is the difference between aerobic and anaerobic respiration?

Answer 1

Aerobic = requires oxygen, produces ATP.

Anaerobic = doesn’t require oxygen, produces less ATP than aerobic.

Both start with glycolysis.

Question 2

Briefly describe the process of glycolysis:

Answer 2

A molecule of glucose is split into two smaller molecules of pyruvate.

Question 3

Where does glycolysis occur?

Answer 3

In the cytoplasm.

Question 4

Does glycolysis take place in aerobic or anaerobic respiration?

Answer 4

The first stage in both.

It doesn’t need oxygen to take place though - so it’s an anaerobic process.

Question 5

What are the two stages in glycolysis?

Answer 5

Phosphorylation and oxidation.

Question 6

In glycolysis, what is there an overall net gain of?

Answer 6

2 ATP and 2 reduced NAD

Question 7

Describe the first stage of glycolysis:

Answer 7

Phosphorylation

• Glucose is phosphorylated using phosphate from ATP - creates 1 molecule of glucose phosphate and 1 molecule of ADP.
• ATP is then used to add another phosphate - hexose bisphosphate forms.
• Hexose bisphosphate is then split into 2 molecules of triose phosphate.

Question 8

Describe the second stage of glycolysis:

Answer 8

Oxidation

• Triose phosphate is oxidised (loses hydrogen) - 2 molecules of pyruvate form.
• NAD collects hydrogen ions, forming 2 reduced NAD.
• 4 ATP are produced, but 2 were used up in stage 1, so there’s a net gain of 2.

Question 9

Draw a diagram of glycolysis:

Answer 9

Question 10

In aerobic respiration, what happens to the:

• two molecules of reduced NAD?
• two molecules of pyruvate?

Answer 10

• Reduced NAD - go to oxidative phosphorylation.
• Pyruvate - actively transported into the matrix of mitochondria for the link reaction.

Question 11

In anaerobic respiration, what is the pyruvate produced in glycolysis converted to?

What aids this?

Answer 11

Ethanol (in plants and yeast) or lactate (in animal cells and some bacteria).

Reduced NAD facilitates this.

Question 12

The production of ethanol or lactate in anaerobic respiration does what?

What does this mean?

Answer 12

Regenerates oxidised NAD.

This means glycolysis can continue even when there isn’t much oxygen around, so a small amount of ATP can still be produced to keep biological processes going.

Question 13

Draw a diagram for alcohol fermentation:

Answer 13

Pyruvate conversion in anaerobic respiration in plants.

Question 14

Draw a diagram of lactate fermentation:

Answer 14

Pyruvate conversion in anaerobic respiration in animals.

Question 15

How many molecules of ATP does glycolysis yield per molecule of glucose?

Answer 15

2

Question 16

Why is pyruvate reduced in the anaerobic respiration of both plants and animals?

Answer 16

To regenerate NAD in its oxidised state.

Question 17

Draw a diagram representing the anaerobic respiration of animals:

Answer 17

• Pyruvate is redcued to lactate, regenerating oxidised NAD.

Question 18

What happens if there is a build up of lactate in the body?

What needs to happen to combat this?

Answer 18

The muscle can cramp.

So, lactate needs to be oxidised back to pyruvate when oxygen is available. The extra oxygen needed for this is known as oxygen debt.

Question 19

Draw a diagram representing the anaerobic respiration of plants and microorganisms:

Answer 19

Question 20

Why does the pH of muscles fall during strenuous exercise?

Answer 20

The cells begin to respire anaerobically, which produces lactate.

This is acidic and so lowers the pH of the muscle.

Question 21

Once oxygen debt has been repaird and all the lactate has been oxidised to pyruvate, what can happen to the pyruvate?

Answer 21

It could go into the link reaction or it can be stored as glycogen.

Question 22

What happens to the ethanol produced during the anaerobic respiration of plants?

Answer 22

It is disposed of as a waste product.