5.7.5 oxidative phosphorylation & chemiosmotic theory

Question 1

define chemiosmosis

Answer 1

flow of protons, down their concentration gradient, across a membrane, through channel associated with ATP synthase

Question 2

where does oxidative phosphorylation happen

Answer 2

mitochondria

Question 3

where are the electron transport chains embedded

Answer 3

inner mitochondrial membrane (cristae)

Question 4

what 3 things happen in oxidative phosphorylation

Answer 4

1. NADH & FADH reoxidised when they deliver their H atoms
2. H atoms released from reduced coenzymes split into electrons & protons
3. protons go into solution in mitochondrial matrix

Question 5

what is the role of the electrons (from hydrogen atoms splitting into electrons & protons)

Answer 5

• pass along chain of electron carriers
• each electron carrier protein has iron ion at it’s core = gain electron & become reduced (Fe2+)
• reduced iron ion donates electron to iron ion in next electron carrier (reoxidised to Fe3+)
• some energy used to pump protons across cristae (into intermembrane space)

Question 6

describe the proton gradient

Answer 6

• accumulate in intermembrane space, forming protein gradient
• proton gradients generate chemiosmotic potential (proton motive force, pmf)
• ATP made using energy of pmf
• protons diffuse through protein channels associated with ATP synthase enzymes = forms ATP

Question 7

describe oxygen as the final electron acceptor

Answer 7

combines with electrons (from electron transport chain) & protons (diffused down ATP synthase) = forms water

4H+ + 4e- + O2 ——» 2H2O

Question 8

how much NADH & FADH is made during respiration (for one glucose molecule)

Answer 8

NADH:
- glycolysis = 2
- link reaction = 2
- krebs cycle = 6

FADH:
- glycolysis = 0
- link reaction = 0
- krebs cycle = 2

Question 9

how many ATP molecules are produced during oxidative phosphorylation

Answer 9

28 (per glucose molecule)

Question 10

total ATP produced per glucose molecule during respiration

Answer 10

32

Question 11

how much ATP is produced during glycolysis, link reaction & the krebs cycle (per glucose molecule)

Answer 11

glycolysis = 2
link reaction = 0
krebs cycle = 2

Question 12

why may the actual yield of ATP be lower during respiration

Answer 12

• some ATP used to actively transport pyruvate into mitochondria
• some ATP used in shuttle system transporting NADH into mitochondria
• some protons leak out through outer mitochondrial membrane