topic 7

Question 1

7.3 Overall equation of aerobic respiration

Answer 1

C6H12O6 + 6O2 –> 6CO2 + 6H2O + energy

Question 2

7.3 What is aerobic respiration?

Answer 2

• process where a large amount of energy is released by splitting glucose into CO2 and H2 (produces H2O)

1. Glycolysis (cytoplasm)
2. Link reaction (mitochondria)
3. Krebs cycle (mitochondria)
4. Oxidative phosphorylation (mitochondria)

Question 3

7.3 Co enzymes involved in aerobic respiration

Answer 3

1. NAD and FAD: transfer H from one molecule to another (reduce or oxidse)
2. Coenzyme A: transfers acetate between molecules

Question 4

7.3 Enzymes in aerobic respiration

Answer 4

• specific intracellular enzyme: controls and catalyses each reaction
• enzyme w slow activity: rate limiting
  (determines overall rate of respiration)

Question 5

7.4 Explain glycolysis

Answer 5

• happens in aerobic and anaerobic respiration
• occurs in the cytoplasm
  1. phosphorylating glucose to GP using 2ATP
  2. production of 3C and 2 ADP
  3. oxidation of 3C to produce 2 pyruvates
  (net gain of 2 ATP and 2 reduced NAD)

Question 6

7.4 Products of Glycolysis

Answer 6

• 2 pyruvate
• net gain of 2 ATP
• 2 reduced NAD

Question 7

7.4 Lactate and anaerobic respiration

Answer 7

• does not use oxygen
• only glycolysis
• lactate fermentation: occurs in animals and produces lactate
  1. glucose convers to pyruvate via glycolysis
  2. reduced NAD transfers H to pyruvate > forms lactate and NAD
  3. NAD reused in glycolysis

Question 8

7.5 Explain the Link reaction

Answer 8

• pyruvate and NADH from glycolysis actively transports into the mitochondrial matrix (NO ATP)
• happens twice for every time pyruvate (3C) gets oxidised
• 2 pyruvate forms 1 glucose molecule
  1. pyruvate decarboxylated (C removed, forms CO2)
  2. NAD reduced (H from pyruvate)
  3. pyruvate changed into acetate
  4. acetate combined with coenzyme A to form acetyl coenzyme

Question 9

7.5 Products of Link reaction (2 pyruvates = 1 glucose)

Answer 9

• 2 acetyl coA
• 2 CO2
• 2 reduced NAD

Question 10

7.5 Explain the Krebs Cycle

Answer 10

• controlled by specific intracellular enzyme in mitochondrial matrix
• cycle happens once every pyruvate (twice for every glucose molecule)
  1. acetyl coA (from link reaction) combines with oxaloacetate to form citrate - coA goes back to link reaction
  2. 6C molecule converted to 5C
  3. decarboxylation occurs (CO2 removed), dehydrogenation occurs (H removed) > produces reduced NAD
  4. 5C molecule converted to 4C
  5. decarboxylation occurs, dehydrogenation occurs > produces 2 reduced NAD and 1 reduced FAD
  6. ATP produced (substrate-level phosphorylation

Question 11

7.5 Products of Krebs Cycle (per glucose - cycle happens twice)

Answer 11

• 6 reduced NAD
• 2 reduced FAD
• 2 ATP
• 4 CO2

Question 12

7.6 What is oxidative phosphorylation?

Answer 12

• formation of ATP in ghe electron transport chain
  1. electron transport chain
  2. chemiosmosis: movement of H+ across membrane down an electrochemical gradient, generates ATP

Question 13

7.6 Explain oxidative phosphorylation

Answer 13

1. H atoms released from reduced NAD and FAD)
2. electrons move down electron transport chain losing energy
3. energy used to pump protons from mitochondrial matrix into inter membrane space
4. concentration of proton is higher forming electrochemical gradient
5. protons move down electrochemical gradient back into mitochondrial matrix via ATP synthase
6. chemiosmosis occurs: movement of H+ across a membrane generating ATP
7. at the end of the e- transport chain, protons, e- and O2 (from blood) combine to form water

Question 14

7.7 Understand what happens to lactate after a period of anaerobic respiration in animals

Answer 14

• oxidised back to pyruvate and enter the Krebs cycle

- taken to the liver, converted back to glucose and stored as glycogen