5.7 - Respiration

Question 1

Explain the electron transport chain:

Answer 1

• The electron transport chain is linked to creation of an electrochemical gradient;
• Hydrogen ions are transferred across the inner membrane via carriers;
• Hydrogen ions are pumped across inner membrane;
• This creates a concentration gradient;
• The electrons are transferred between carriers;
• Chemiosmosis - hydrogen ions passed down concentration gradient;
• Through ATPase complex;
• Oxygen is final electron acceptor forming water;

Question 2

Explain oxidative phosphorylation in terms of chemiosmosis.

Answer 2

• electrons release energy as they pass along the chain;
• oxygen final electron acceptor;
• production of water;
• builds up proton gradient / protons pumped across inner membrane;
• protons flow into matrix of mitochondria through ATPase;
• ATP produced;
• produces 32 ATP (per glucose);

Question 3

Suggest why having more proton pores in the inner mitochondrial membrane would result in a person being less likely to gain weight?

Answer 3

• More proton pores would result in protons leaking back into the matrix without producing ATP.
• Less ATP would be made from oxidative phosphorylation.
• Because the energy from chemiosmosis is decoupled from ATP synthesis.
• So food would not be converted to ATP as efficiently
• So less deposition of excess food at fat in the body
• Some fat stores may need to be respired to provide enough energy
• More energy would be wasted as heat

Question 4

Summarise the importance of coenzymes in respiration. Include details of the molecules and the processes involved.

Answer 4

• Coenzyme A
  Transfers Acetyl from the link reaction to the Krebs cycle
• ADP/ATP
• Phosphorylation of glucose to form Hexose 1,6 Bisphosphate in glycolysis
• ADP removes a phosphate group from TP in glycolysis
• ADP removes a phosphate group from intermediated compound in the Krebs cycle
• Formation of ATP by substrate level phosphorylation
• Formation of ATP by oxidative phosphorylation, harnessing the chemical energy from chemiosmosis
• NAD
• Removal of hydrogen and electrons from triose phosphate in glycolysis
• Removal of hydrogen and electrons from pyruvate in the link reaction