Anaerobic Respiration

Obligate Anaerobes

Cannot survive in oxygen

• Most are prokaryotes

Facultative Anaerobes

Use aerobic resp. when in oxygen, but use anaerobic resp. when no oxygen available

• E.g. yeast

Obligate Aerobes

Only synthesise ATP w. O2 present

• Individual cells can cope for a little while without

• E.g. mammals

What doesn’t anaerobic respiration go thru like aerobic does?

Link reaction, Krebs cycle, Oxidative Phosphorylation

Fermentation

The process by which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an ETC

What are the 2 processes of anaerobic resp. known as and what do they differ by?

• Lactate Fermentation

• Alcoholic Fermentation

Differ in which organisms they occur in and what happens to the pyruvate.

What organisms use which anaerobic pathway?

• Yeast and some plant root cells use ethanol fermentation

• Mammalian muscle cells and other microorganisms use lactate fermentation

How are small amount of ATP produced during anaerobic resp.?

• Some cells oxidise red. NAD produced during glycolysis so it can be used for further H transport

• Glycolysis continues, producing small amount of ATP

  • Synthesised by substrate-level phosphorylation only

• NOTE: Glucose is not fully broken down, hence the less ATP

Lactate Fermentation

1. NAD accepts H+ in glycolysis

2. Pyruvate accepts H+ from red. NAD, forming lactate + NAD

   • Pyruvate reduced to lactate

   • Catalysed by lactate dehydrogenase

3. NAD regenerates to be used again in glycolysis

What happens once lactate is produced?

1. Converts to lactic acid

2. Transported to liver in bloodstream

3. Liver uses oxygen to convert lactic acid into pyruvate, then glucose

Can be converted into glycogen tho

Why can’t lactate fermentation occur indefinitely?

• Only 2 ATP made; isn’t enough to maintain vital processes for a long time

• Accumulation of lactic acid decreases pH, protein structures/ enzymes denature, & cease to function

Why do we breathe deeper and faster after exercise?

Oxidation of lactate to pyruvate requires extra oxygen

• Referred to as an ‘oxygen debt’

Lactate fermentation image

Alcoholic fermentation

1. Pyruvate converted to ethanal, catalysed by pyruvate decarboxylase

2. Ethanal accepts H+ from red. NAD, to make ethanol

3. Ethanol is final product, builds up to 15% before killing yeast

4. NAD regenerates, continues to act as coenzyme, glycolysis continues

Difference in time anaerobic processes last

• Alcoholic fermentation is NOT short-term and an continue indefinitely in the absence of oxygen

• Lactate fermentation is short-term and CANNOT continue indefinitely in the absence of oxygen

Alcohol Fermentation image

Benefit of anaerobic respiration

• Used when oxygen cannot be supplied fast enough to respiring cells

• It is a temporary emergency measure to keep vital processes functioning

Experiment with yeast

Check textbook, and sme