B.9.1 Compare aerobic and anaerobic respiration of glucose in terms of oxidation/reduction and energy released
Step 1: Glycolysis
Conversion of Pyruvate:
- in aerobic respiration, glucose is converted into pyruvate, which, in the presence of oxygen, changes to carbon dioxide and water
- overall, glucose undergoes oxidation and oxygen undergoes reduction
- in anaerobic respiration, pyruvate is converted to lactate in human beings, while yeast converts pyruvate to ethanol and carbon dioxide
Step 1: Glycolysis
- sugar --> pyruvate (C3H3O3-)
- 1) C6H12O6 + 2NAD+ --> 2C3H3O3- + 2NADH + 4H+ + energy
- note: catabolism is the breaking down of larger molecules in smaller ones
- NAD+ undergoes reduction: NAD+ + H+ + 2e- --> NADH
- glucose undergoes oxidation: C6H12O6 --> C3H3O3- + 2e-
Conversion of Pyruvate:
- after pyruvate is formed in both aerobic and anaerobic respiration, it's metabolized differently now
- in aerobic, it goes through the krebs cycle and electron transport chain
- 2CH3COCOO- + 2NADH + 4H+ + 6O2 --> 6CO2 + 6H2O + 2NAD+
- overall for aerobic respiration: C6H12O6 + 6O2 --> 6CO2 + 6H2O deltaH = -2820 kJ/mol
- in anaerobic respiration, only 2 ATP produced for same amount of C6H12O6
- CH3COCOO- + NADH + H+ --> CH3CHOHCOO- (lactic acid) + NAD+ + energy
- NADH is oxidized: NADH + H+ --> NAD+ + 2H+ + 2e-
- pyruvate is reduced: CH3COCOO- + 2H+ + 2e- --> CH3CHOHCOO-
- the more lactic acid builds up, the lower the pH, causing cramps in muscles
- if oxygen deprivation is temporary, lactic acid will be further metabolized
- C3H6O3 + 3O2 --> 3CO2 + 3H2O + energy
B.9.2 Outline the role of copper ions in electron transport and iron ions in oxygen transport
Hemoglobin (Fe):
Cytochromes (Cu):
- micronutrients include Fe, Cu, Mn, etc.
- Fe is needed for hemoglobin, Cu is needed for electron transport, and Co is needed for vitamin B12
- these transition metal ions have multiple oxidation states
Hemoglobin (Fe):
- Fe2+ is a Lewis acid and forms a complex ion (multidentate)
- Fe2+ temporarily oxidized to Fe3+
- O2 is able to bind via a dative covalent bond, allowing for oxygen transport
Cytochromes (Cu):
- cytochromes are part of the electron transport chain, which generates ATP (energy)
- electrons are transported between proteins down the transport chain
- Cu1+ is oxidized to Cu2+ and then reduced back to Cu1+, repeating in a cycle
- Cu is involved with cytochrome oxidase, the enzyme that is the final carrier in the chain
- NADH carries H+ and e- from the metal ions