Metabolism

Question 1

Obeying thermodynamics

Answer 1

• A reaction can only occur spontaneously if delta G is negative because that is when it is favourable - you can couple the unfavourable reactions with favourable ones so it becomes spontaneous

Question 2

ATP (adenosine triphosphate)

Answer 2

• Used to make reactions more favourable
• Triphosphate is where the energy is stored
• Adenosine is more for recognisition so things can hold onto the molecule

Question 3

Glycolysis

Answer 3

1. Glycose gets phosphorylated, this uses ATP
2. The phosphorylated glucose is isomerised to fructose equivalent and this prepares it for being broke into two C3 fragments
3. The fructose is phosphorylated again by another kinase using ATP
4. The molecule is split in half by a retro-aldol reaction, and one half is isomerised
5. The molecule is oxidised and phosphylated with consumption of NAD+ and Pi to give NADH
6. There are then two phosphoryl transfers onto ADP to produce two molecules of ATP

Question 4

Citric acid/Krebs cycle

Answer 4

• Pyruvate diffuses from the cytosol into the matrix of the mitochondria
• Need to convert pyruvate into acetyl CoA
• Acetyl CoA is oxidised to form CO2 and coenzymes which generate ATP

Question 5

Oxidative phosphorylation

Answer 5

• NADH produced by the citric acid cycle are subject to oxidation by oxygen and this produces ATP
• Electrons from NADH are passed through membrane proteins on the critae of mitochondria, pumping H+ out as they go, eventually recombining with O2
• The resultant imbalance of H+ across the membrane drives ATP synthase as protons flow back through the protein