Respiration

Question 1

Where does glycolysis occur?

Answer 1

cytoplasm

Question 2

What type of respiration occurs during glycolysis?

Answer 2

anaerobic (oxygen NOT required)

Question 3

Describe the process of glycolysis

Answer 3

1) Phosphorylation of glucose to glucose phosphate
- using the inorganic phosphates from 2 ATP
2) Hydrolysed to 2 X triose phosphate
3) 2X triose phosphate become oxidised to 2X pyruvate
- 2 NAD reduced (gains hydrogen ions)
- 4 ATP regenerated
4 gained - 2 used = net production of 2 ATP

Question 4

What happens after glycolysis if no oxygen is present? (anaerobic respiration)

Answer 4

• Pyruvate is converted to lactate (animal cells, some bacteria) or ethanol (plants, yeast)
• Oxidising reduced NAD → NAD regenerated
• So glycolysis continues which needs NAD

Question 5

What happens after glycolysis is oxygen is present? (aerobic respiration)

Answer 5

• Pyruvate is actively transported out the mitochondrial matrix

Question 6

What are the 4 stages of aerobic respiration?

Answer 6

1. glycolysis
2. link reaction
3. krebs cycle
4. oxidative phosphorylation

Question 7

Where does the link reaction occur?

Answer 7

in the mitochondrial matrix

Question 8

What happens in the link reaction? (aerobic)

Answer 8

• Pyruvate is oxidised and decarboxylated to form acetate
• CO2 and reduced NAD is produced
• Acetate combines with coenzyme A → Acetyl Coenzyme A

Question 9

Where does the krebs cycle occur?

Answer 9

mitochondrial matrix

Question 10

What happens in the Krebs Cycle reaction?

Answer 10

• Acetyl CoA reacts with a 4C molecule producing a 6 carbon molecule
• Co-enzyme A is released and goes back to the link reaction
• 6C → 5C → 4C (4C molecule is regenerated) through decarboxylation and dehydrogenation (producing 2x NADH and
  1x FADH)
• ATP is produced by substrate level phosphorylation (direct transfer of Pi to ADP)

Question 11

What are the products of the Krebs Cycle

Answer 11

• 2x CO2
• 2x NADH
• 1x FADH
• 1x ATP

Question 12

substrate level phosphorylation

Answer 12

the direct transfer of a phosphate group to an ADP

Question 13

Where does oxidative phosphorylation occur?

Answer 13

mitochondrial matrix

Question 14

What happens during oxidative phosphorylation?

Answer 14

1) Reduced NAD and Reduced FAD are oxidised → releases H+ atoms and electrons
2) Electrons are transferred down the electron transport chain
3) Energy is used by electron carriers to pump protons against conc gradient from the mitochondrial matrix into the intermembrane space by active transport
4) Concentration of protons are higher in the intermembrane space now, this forms an electrochemical gradient
5) Protons move down the electrochemical gradient via ATP synthase back into the matrix
6) Releases energy for ADP + Pi → ATP
7) Oxygen is the final electron acceptor → protons, electrons and oxygen combine to form water)

Question 15

What way does electrons move in oxidative phosphorylation?

Answer 15

1) Via active transport, electrons move into the intermembrane space from the matrix
2) higher conc in the intermembrane space
3) electrons move down electrochemical gradient via ATP synthase back into the matrix

Question 16

What does it mean when it says ‘oxygen is the final electron acceptor’ ?

Answer 16

protons, electrons and oxygen combine to form water

Question 17

What are the products of Oxidative Phosphorylation?

Answer 17

• Water
• ATP