Respiration

Question 1

Name the four steps in aerobic respiration

Answer 1

• Glycolysis
• Link reaction
• Krebs cycle
• oxidative phosphorylation

Question 2

Define aerobic respiration

Answer 2

• Requires oxygen

- Produces CO2, water and 38 ATP

Question 3

Describe the two stages of gylcolysis

Answer 3

Posphorylation
-2 phosphates are added from 2 ATP to glucose
-This creates 2 molecules of ADP and 2 of triose phosphate
Oxidation
-Triose phosphate is oxidised by NAD, to form 2 pyruvate and 2 reduced NAD
-4 ATP are produced, giving a net gain of 2 ATP

Question 4

Describe the link reaction

Answer 4

• Pyruvate is decarboxylated (one C removed as CO2)
• NAD is reduced by the pyruvate, making reduced NAD and acetate
• CoA combines with the acetate to make acetyl CoA
• Occurs twice (as 2 pyruvate from glycolysis)
• No ATP produced

Question 5

Describe what happens in alcoholic anaerobic respiration

Answer 5

• Pyruvate converted to ethanal by yeast

- Ethanal converted to ethanol by reacting with reduced NAD to make NAD for use in glycolysis again

Question 6

Describe what happens in cellular anaerobic respiration (animals)

Answer 6

• Pyruvate reacts with reduced NAD to produce lactic acid

- NAD used in glycolysis again (cyclical)

Question 7

Describe the 4 steps in the Krebs cycle

Answer 7

• Acetyl CoA from link reacts with a 4C chain to produce a 6C chain. CoA returns to link to be reused
• 6C chain is converted to a 5C chain by NAD (which is reduced), and CO2 is given off
• 5C chain is converted to a 4C chain, producing one reduced FAD and two reduced NAD
• ATP is also formed from an intermediate compound and ADP. This is substrate level phosphorylation.

Question 8

Describe the steps in oxiditave phosphorylation

Answer 8

• Hydrogen atoms are released from the reduced NAD and FAD as they are oxidised to NAD and FAD. The H atomes split into H+ and e-
• The electrons move along the ETC, losing energy at each electron carrier.
• Energy lost is used to pump protons from the mitochondrial matrix into the intermembrane space
• High H+ concentration in the intermembrane space forms a concentration gradient of ions
• Protons move down the gradient (called chemiosmosis) through ATP synthase which drives the synthesis of ATP
• The protons combine with electrons from the ETC and O2 from the blood to make water