Topic 7A (aerobic and anaerbic respiration, krebs cycle, chemiosmosis)

Describe how chemiosmosis is involved in the synthesis of ATP

(5 marks)

- H+ ions and electrons are transported to the ETC

- via reduced NAD and FAD (coenzymes), this allows H+ ions to be pumped to intermembrane space

- creating an electrochemical gradient

- H⁺ ions/ protons move through ATP synthase

- this gives the energy needed to catalyse the conversion of ADP + Pi into ATP

(aka → phosphorylation of ADP)

• ATP ❌ → made using ATP synthase; oxygen is not directly added.
  

• CO₂ ❌: produced from decarboxylation in the link reaction/Krebs cycle. oxygen originates from other sources
  

• Reduced NAD ❌ → NAD accepts hydrogen/electrons, not oxygen.
  
  
  water ✅:
  O₂ is used in respiration (in ETC), where it accepts electrons and H⁺ to form water
  thus water is the first to have radioactive O atoms.

because:

ETC inhibited, therefore less H+ pumped and thus less ATP produced
also less o2 accepts e- [Oxygen is the final electron acceptor]

more anaerobic respiration(glycolysis and fermentation) occurs so more lactate is produced

Anaerobic respiration summary:

1 glucose → phosphorylation of glucose → splits into two 3C molecules → converted to form 2 pyruvate → 2 lactate molecules

→ phosphorylation is addition of phosphate group, i.e to glucose which is a hexose sugar as its 6C

ANS: phosphorylation of hexoses (like glucose) ✅

State what is meant by Decarboxylation, Oxidation and Phosphorylation

Decarboxylation = removal of CO₂ molecule from a compound

Oxidation = loss of electrons (also: gain of o2 and loss hydrogen atoms)

Phosphorylation = addition of a phosphate group to a molecule

(e.g. ADP + Pi → ATP)

link reaction produces 2 molecules of acetyl CoA which are 2C (and 2 molecules of NADH)
[2C = 2 carbon containing]