5.7.9 Anaerobic respiration

Question 1

List several consequences when there is not enough oxygen available for respiration

Answer 1

• No final acceptor of electrons from ETC
• ETC stops functioning
• No more ATP produced via oxidative phosphorylation
• NADH and FADH2 arent oxidised by electron carrier
• No oxidised NAD and FAD are available for dehydrogenation in Krebs cycle
• Krebs cycle stops

Question 2

What is anaerobic respiration

Answer 2

A way for cells to produce some ATP in low oxygen conditions

Question 3

How can cells ensure that glycolysis can continue in the absence of oxygen

Answer 3

Some cells are able to oxidise the reduced AND produced during glycolysis so it can be used for further H transport.
This means glycolysis can continue and ATP is produced

Question 4

Describe the overall anaerobic pathway

Answer 4

Some cells - oxidise reduced AND produced in glycolysis = can be used for further H transport
Glycolysis can continue and small amounts of ATP are still produced
Different cells use different pathways:
- Yeast/microorganisms = ethanol fermentation
- Microorganisms/mammalian muscle cells = lactate fermentation

Question 5

What are the two anaerobic pathways?

Answer 5

Yeast/microorganisms = ethanol fermentation
Microorganisms/mammalian muscle cells = lactate fermentation

Question 6

Describe the process of ethanol fermentation

Answer 6

(Reduced NAD - transfers H to ethanal to form ethanol)

In the first step pyruvate is decarboxylated to ethanal - producing CO2

Ethanal is reduced to ethanol by alcohol dehydrogenase

Ethanal is final electron acceptor

Ethanol cannot be further metabolised = waste product

Question 7

Describe the process of lactate fermentation

Answer 7

(Reduced NAD transfers H to pyruvate to form lactate)

Pyruvate is reduced to lactate by enzyme lactate dehydrogenase

Pyruvate is final electron acceptor

Final product of lactate can be further metabolised

Question 8

How many steps does the process of ethanol fermentation have?

Answer 8

Two

Question 9

What happens after lactate is produced?

Answer 9

1. Oxidised back to pyruvate - channeled into krebs cycle
   - This needs extra oxygen - referred to as O2 debt (animals breathe deeper/faster after exercise)
2. Converted into glycogen (cori cycle) for storage in liver

Question 10

How many steps does the process of lactate fermentation have?

Answer 10

One

Question 11

How many steps does the process of ethanol fermentation have?

Answer 11

Two

Question 12

What is produced alongside the waste ethanol

Answer 12

Carbon dioxide