What are the four stages of aerobic respiration?
- glycolysis
- link reaction
- Krebs cycle
- electron transport chain
Where does glycolysis take place?
In the cytosol of the cell membrane
Describe the three main stages of glycolysis
- Phosphorylation of glucose = hydrolysis of 2 ATP molecules provides a phosphate and a 6C sugar becomes the 6C hexose bisphosphate that is formed and this is unstable.
- The splitting of the 6C hexose bisphosphate into two 3C triose phosphate molecules
- The oxidation of each triose phosphate into 3C pyruvate through the loss of hydrogen. ATP is produced by substrate level phosphorylation in this process (2 ATP for triose phosphate)
What does glycolysis produce?
- 4 ATP
- 2 molecules of NADH2
- 2 pyruvates
Where does the link reaction take place?
in the matrix of the mitochondria
What are the stages of the link reaction?
- 3C pyruvate is converted into 2C acetate through loss of CO2
- CO2 produced through action of decarboxylase
- hydrogen lost through action of dehydrogenase enzyme
- NAD reduced by hydrogen to NADH2
- 2C acetate is activated by combining with co-enzyme A to produce acetyl co-enzyme A
How many times does the link reaction take place and why?
Twice. Glycolysis produces two molecules of 3C pyruvate
Where does the krebs cycle take place?
in the matrix of the mitochondria
What are the stages of the Krebs cycle?
- the 2C acetate fragment of the acetyl co-enzyme A combines with a 4C compound to produce a 6C compound which regenerates co-enzyme A
- the 4C compound is regenerated through a series of 6C and 5C intermediates where two atoms of carbon are lost in two molecules of CO2 (the oxygen comes from H2O)
- 8 hydrogen atoms are lost (4 pairs) and they reduce NAD and FAD
- 3 molecules of NADH2 and one molecule of FADH2 are produced in one cycle
- one molecule of ATP is produced by substrate level phosphorylation in one cycle.
What does the link reaction produce?
2 x NADH2
What does the Krebs cycle produce?
- 2 x ATP
- 6 x NADH2
- 2 x FADH2
Where does the electron transport chain take place?
Inner mitochondrial membrane
What is the final electron acceptor of the ETC in respiration?
Oxygen
How much ATP is produced from one molecule of glucose?
38 ATP
How many ATP does a molecule of NADH2 make?
3 ATP
How many ATP does a molecule of FADH2 make?
2 ATP
What part of respiration occurs anaerobically?
Glycolysis
What is the process of anaerobic respiration?
- Lactic acid fermentation - after glycolysis NADH2 transfers hydrogen to pyruvate to form lactic acid
- Lactic acid production is reversible if oxygen becomes available - the amount of oxygen needed to remove lactic acid is called the oxygen debt
What is the yield of ATP in anaerobic respiration
2 ATP
