5.7.9 Anaerobic Respiration Flashcards
What are the consequences when there is not enough oxygen for respiration?
Sometimes cells experience conditions with little or no oxygen
There are several consequences when there is not enough oxygen available for respiration:
There is no final acceptor of electrons from the electron transport chain
The electron transport chain stops functioning
No more ATP is produced via oxidative phosphorylation
Reduced NAD and FAD aren’t oxidised by an electron carrier
No oxidised NAD and FAD are available for dehydrogenation in the Krebs cycle
The Krebs cycle stops
However, there is still a way for cells to produce some ATP in low oxygen conditions through anaerobic respiration
What are anaerobic pathways?
Some cells are able to oxidise the reduced NAD produced during glycolysis so it can be used for further hydrogen transport
This means that glycolysis can continue and small amounts of ATP are still produced
Different cells use different pathways to achieve this
Yeast and microorganisms use ethanol fermentation
Other microorganisms and mammalian muscle cells use lactate fermentation
What is ethanol fermentation?
In this pathway reduced NAD transfers its hydrogens to ethanal to form ethanol
In the first step of the pathway pyruvate is decarboxylated to ethanal
Producing CO2
Then ethanal is reduced to ethanol by the enzyme alcohol dehydrogenase
Ethanal is the hydrogen acceptor
Ethanol cannot be further metabolised; it is a waste product
Look at SME for diagram
What is lactate fermentation?
In this pathway reduced NAD transfers its hydrogens to pyruvate to form lactate
Pyruvate is reduced to lactate by enzyme lactate dehydrogenase
Pyruvate is the hydrogen acceptor
The final product lactate can be further metabolised
Look at SME for diagram
What is the metabolization of lactate?
After lactate is produced two things can happen:
It can be oxidised back to pyruvate which is then channelled into the Krebs cycle for ATP production
It can be converted into glycogen for storage in the liver
The oxidation of lactate back to pyruvate needs extra oxygen
This extra oxygen is referred to as an oxygen debt
It explains why animals breathe deeper and faster after exercise
