5.2 Respiration

Question 1

Why is respiration important?

Answer 1

• Produces ATP to release energy
• For active transport, protein synthesis, etc

Question 2

How are mitochondria structured?

Answer 2

• Membrane-bound organelle
• Outer membrane, intermembrane space, inner membrane / cristae
• Matrix containing circular DNA and 70s ribosomes

Question 3

What happens during glycolysis?

Answer 3

• Glucose is phosphorylated to glucose phosphate using 2 ATP
• Glucose phosphate is hydrolysed to 2 triose phosphate
• Triose phosphate oxidised to pyruvate
• 2 NAD reduced and 4 ATP regenerated (net gain of 2 ATP)

Question 4

What happens after glycolysis if respiration is anaerobic?

Answer 4

• Pyruvate is reduced into lactate (animals and bacteria) or ethanol and CO2 (plants and yeast)
• NADH is oxidised, regenerating NAD
• So glycolysis can continue

Question 5

What happens after glycolysis if respiration is aerobic?

Answer 5

Pyruvate is actively transported into the mitochondria matrix

Question 6

What happens during the link reaction?

Answer 6

• Pyruvate is oxidised to acetate
• NAD is reduced and CO2 produced
• Acetate combines with coenzyme A to form acetyl coenzyme A

Question 7

What happens during the Krebs cycle?

Answer 7

• Acetyl coenzyme A reacts with a 4C molecule to produce a 6C molecule
• Releasing coenzyme A
• In a series of oxidation-reduction reactions the 4C molecule is regenerated
• 2 CO2 are lost, 3 NAD are reduced and 1 FAD is reduced
• ATP undergoes substrate level phosphorylation

Question 8

What happens during oxidative phosphorylation?

Answer 8

• NADH and FADH are oxidised, releasing H+ and electrons
• Electrons move along the electron transport chain, releasing energy
• This energy is used to actively transport protons into intermembrane space
• Protons diffuse down their electrochemical gradient into matrix via ATP synthase
• Releasing energy which is used to join ADP + Pi to form ATP
• Oxygen is the final electron acceptor, combining with protons, electrons and oxygen to form water

Question 9

What are some other respiratory substrates?

Answer 9

• Lipids hydrolysed to fatty acids which are converted to acetyl coenzyme A
• Proteins hydrolysed to amino acids which are converted to intermediates in Krebs cycle