5- anaerobic respiration

What is anaerobic respiration?

The release of energy from glucose without oxygen, producing a small amount of ATP.

Why does the electron transport chain stop without oxygen?

Oxygen is the final electron acceptor, so without it electrons cannot leave the chain.

Why cannot NADH be oxidised without oxygen?

Electrons cannot pass to oxygen, so NADH cannot unload hydrogen.

Why does respiration stop without NAD?

NAD is needed as a coenzyme for glycolysis and the Krebs cycle.

How does anaerobic respiration prevent respiration from stopping?

It regenerates NAD from NADH, allowing glycolysis to continue.

Where does anaerobic respiration occur in the pathway?

As an extra step after glycolysis.

How much ATP does anaerobic respiration produce per glucose?

2 ATP.

How is ATP made in anaerobic respiration?

By substrate-level phosphorylation in glycolysis.

What is substrate-level phosphorylation?

Direct synthesis of ATP from ADP using enzyme-catalysed reactions.

What happens to pyruvate in lactic acid fermentation?

Pyruvate is reduced to lactate.

Which coenzyme is used in lactic acid fermentation?

NADH is oxidised to regenerate NAD.

In which organisms does lactic acid fermentation occur?

Animals and some bacteria.

Name two human cell types that use lactic acid fermentation.

Muscle cells and red blood cells.

Is lactic acid fermentation reversible?

Yes, lactate can be oxidised when oxygen becomes available.

Why does lactic acid fermentation cause muscle fatigue?

Lactate lowers pH, slowing enzyme activity.

Why cannot lactic acid fermentation continue for long periods?

Low pH inhibits enzymes in muscle cells.

What is ethanolic fermentation?

Anaerobic respiration in plants and fungi that produces ethanol and carbon dioxide.

What happens to pyruvate in ethanolic fermentation?

Pyruvate is converted to ethanol and carbon dioxide.

Which coenzyme is regenerated in ethanolic fermentation?

NAD is regenerated from NADH.

Is ethanolic fermentation reversible?

No, the energy in ethanol cannot be retrieved by the cells.

Why is ethanolic fermentation irreversible?

Carbon dioxide is lost from the reaction.

Which organisms use ethanolic fermentation?

Plants and fungi, including yeast.

How is ethanolic fermentation used by humans?

In brewing and baking to produce ethanol and carbon dioxide.

Does anaerobic respiration use the electron transport chain?

No.

Does anaerobic respiration require oxygen?

No.

What is the final electron acceptor in anaerobic respiration?

There is no final electron acceptor.

How much ATP does aerobic respiration produce per glucose?

About 32 ATP.

Why does aerobic respiration produce more ATP than anaerobic respiration?

It uses oxidative phosphorylation in the electron transport chain.