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Summary A* level AQA second year biology notes
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- Year 2 notes
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- AQA
Concise notes for the second year of A level biology. I got an A* with these notes.
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A2 biology notes3.5.2 Respiration
Glycolysis:
Where: cytoplasm
Stages:
- Glucose glucose phosphate (2ATP 2ADP + Pi)
- Glucose phosphate 2x triose phosphate
- 2x triose phosphate 2x pyruvate
(NAD reduced NAD [2 per glucose])
ADP + Pi ATP [2 per pyruvate, 4 per glucose] NB: substrate level phosphorylation
Overall stats for glycolysis:
products: 2x pyruvate
Net gain of ATP: 2 molecules per glucose
Other products?: 2 reduced NAD per glucose
Link reaction
Stages:
- Pyruvate: undergoes decarboxylation and reduction
o 1x NAD reduced NAD, CO2 produced
- This forms acetate
- Acetate then binds with Co-enzyme A to form Acetyl co-enzyme A
Overall stats for link reaction:
Products: 2x acetyl coenzyme A
Net gain of ATP: 0
Other products: 2 reduced NAD per glucose, 2 CO2 per glucose
, Krebs cycle
Stages:
- Dissociates with co-enzyme A
- Acetate (2C) binds with a 4C sugar forming a 6C sugar
- 6 carbon sugar is then decarboxylated (twice) into 2CO2
- 3 NAD also are reduced into reduced NAD (per acetyl Co-A)
- 1 FAD reduced to reduced FAD (per acetyl Co-A)
- 1 ATP (oxidative phosphorylation)
Overall stats:
Products (per glucose) :
- 2x 3 reduced NAD
- 2x 2 CO2
- 2x 1 reduced FAD
- 2x ATP
Oxidative phosphorylation
1. Reduced NAD is oxidised by the first protein in the ETC this means a hydrogen is removed.
The hydrogen then splits into a proton and electron
2. The proton goes into the matrix, and the electron binds to a protein in the CSM
3. The electron passes along the ETC, in a series of redox reactions (loosing energy as it moves
down energy levels)
4. Some of this energy actively pumps H+ into intermembrane space (the rest is lost as heat)
5. When the H+ diffuses back into the matrix, the ATP synthase molecule spins, producing ATP
through chemiosmosis
6. Oxygen is the final electron and proton acceptor forming H2O
Why u need o2:
- Atp is formed as the electrons move along the ETC
- With the O2 acting as the final electron acceptor
- Without the o2 accepting them, electrons cant be passed along the chain
Note: other respiratory substrates (products from the breakdown of lipids and amino acids) can
enter the Krebs cycle and be used
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