12: Respiration

Question 1

4 key stages of aerobic respiraton

Answer 1

1) Glycolysis
2) Link reaction
3) Krebs cycle
4) Oxidative phosphorylation

Question 2

Where does each of the four stages occur in aerobic respiration

Answer 2

1) Glycolysis (cytoplasm)
2) Link reaction (mitochondrial matrix)
3) Krebs cycle (mitochondrial matrix)
4) Oxidative phosphorylation (mitochondrial inner membrane cristae)

Question 3

Glycolysis

Answer 3

• respiration produces ATP
• first stage of aerobic and anaerobic
• occurs in cytoplasm and is an anaerobic process
  1) Phosphorylating glucose into glucose phosphate using 2 ATP (6C)
  2) The production of triose phosphate (2x3C)
  3) Oxidation of TP to produce pyruvate, and 4 ATP and reduced NAD (coenzyme)
  4) Pyruvate and NADH actively transported into mitochondrial matrix

Question 4

Products of glycolysis

Answer 4

• 2x pyruvate
• net gain 2 ATP
• 2x NADH

Question 5

Link reaction

Answer 5

1) Pyruvate (3C) (from glycolysis) oxidised to make acetate (2C), NAD is oxidised to NADH and 1C lost to co2
2) acetate combines with co-enzyme A to form acetylcoenzyme A
3) for every glucose molecule there are 2 pyruvates created which creates 2x acetylcoA, 2x co2, 2x NADH

Question 6

Krebs cycle

Answer 6

1) Acetyl coA combines with a 4 carbon molecule, releasing coenzyme A (to be used again) and producing a 6 carbon molecule that enters the krebs cycle
2) then a series of redox reactions, cycle generates reduced co-enzymes and ATP by substrate level phosphorylation and co2 is lost
3) the products PER CYCLE: 3x reduced NAD, 1x reduced FAD, 1x ATP, 2x CO2 (cycle happens twice for glucose molecule)

Question 7

Oxidative phosphorylation

Answer 7

• where most atp is produced
• in mitochondrial matrix the reduced co-enzymes release their hydrogen and that splits into protons and electrons
• electrons transported across electron transport chain which releases energy to actively transport the protons from the matrix into the intermembrane space
• this creates an electrochemical gradient so the protons move by facilitated diffusion, down the conc grad through the atp synthase
• the atp synthase phosphorlylates adp to create ATP
• creates 34 atp molecules
• at end of electron transport chain, electrons picked up by oxygen. also picks up protons once passed through to create water

Question 8

Anaerobic respiration

Answer 8

• absence of oxygen, occurs only in the cytoplasm
• pyruvate produced in glycolysis is reduced to form ethanol and co2 or lactate by gaining the h from reduced nad
• this oxidises nad so it can be reused in glycolysis so more atps produced so you can still respire
• build up of lactate will denature enzymes involved in glycolysis