HC2 Metabolism II - Respiration
& Biosynthesis (BOOK)
Chapter 3.8-3.15
CH3 Microbial Metabolism
3.8 Glycolysis and fermentation
Fermentation is a form of anaerobic catabolism in which organic compounds both donate electrons
and accept electrons, and redox balance is achieved without the need for external electron
acceptors.
Respiration is a form of aerobic or anaerobic catabolism in which an organic or inorganic electron
donor is oxidised with O2 (aerobic) or some other compound (anaerobic) functioning as electron
acceptors.
Glycolysis is the oxidation of glucose into pyruvate.
Substrate-level phosphorylation is a process where energy-rich phosphate bonds are transferred to
ADP to form ATP.
Glycolysis consists of three stages:
1. Prepatory reactions: not redox and do not release energy but form a key intermediate
2. Redox reactions occur, energy is conserved and two molecules of pyruvate are formed
3. Redox balance is achieved and fermentation products are formed.
Fermentation
, During glycolysis, glucose is consumed, ATP made and fermentation products generated. For
organisms, fermentation products is waste, but humans use these fermentation products for other
purposes like baking.
3.9 Respiration: citric acid and glyoxylate cycles
Besides fermentation, glucose can also be respired. First glucose is catabolised through glycolysis but
instead of reducing pyruvate to fermentation products, it is fully oxidised to CO2.
The pathway by which pyruvate is oxidised to CO2 is called the citric acid cycle (CAC):
The CAC is also important for other things in the cell besides combusting pyruvate to CO2.
The other function is the biosynthesis of key metabolites. The CAC is thus important for glucose
respiration coupled to energy conservation and the biosynthesis of key metabolites.
Glyoxylate cycle
When acetate is used as an electron donor, the glyoxylate cycle (variation on CAC) becomes active
and functions to replenish oxaloacetate which is in this case used for biosynthesis. Because when
oxaloacetate can’t be regenerated each cycle, the CAC cycle doesn’t work.
& Biosynthesis (BOOK)
Chapter 3.8-3.15
CH3 Microbial Metabolism
3.8 Glycolysis and fermentation
Fermentation is a form of anaerobic catabolism in which organic compounds both donate electrons
and accept electrons, and redox balance is achieved without the need for external electron
acceptors.
Respiration is a form of aerobic or anaerobic catabolism in which an organic or inorganic electron
donor is oxidised with O2 (aerobic) or some other compound (anaerobic) functioning as electron
acceptors.
Glycolysis is the oxidation of glucose into pyruvate.
Substrate-level phosphorylation is a process where energy-rich phosphate bonds are transferred to
ADP to form ATP.
Glycolysis consists of three stages:
1. Prepatory reactions: not redox and do not release energy but form a key intermediate
2. Redox reactions occur, energy is conserved and two molecules of pyruvate are formed
3. Redox balance is achieved and fermentation products are formed.
Fermentation
, During glycolysis, glucose is consumed, ATP made and fermentation products generated. For
organisms, fermentation products is waste, but humans use these fermentation products for other
purposes like baking.
3.9 Respiration: citric acid and glyoxylate cycles
Besides fermentation, glucose can also be respired. First glucose is catabolised through glycolysis but
instead of reducing pyruvate to fermentation products, it is fully oxidised to CO2.
The pathway by which pyruvate is oxidised to CO2 is called the citric acid cycle (CAC):
The CAC is also important for other things in the cell besides combusting pyruvate to CO2.
The other function is the biosynthesis of key metabolites. The CAC is thus important for glucose
respiration coupled to energy conservation and the biosynthesis of key metabolites.
Glyoxylate cycle
When acetate is used as an electron donor, the glyoxylate cycle (variation on CAC) becomes active
and functions to replenish oxaloacetate which is in this case used for biosynthesis. Because when
oxaloacetate can’t be regenerated each cycle, the CAC cycle doesn’t work.
