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Date	May 2017	Marks available	4	Reference code	17M.2.HL.TZ1.5
Level	Higher level	Paper	Paper 2	Time zone	Time zone 1
Command term	Outline	Question number	5	Adapted from	N/A

Question

Oxygen is needed to complete aerobic cell respiration.

Explain how chemical energy for use in the cell is generated by electron transport and chemiosmosis.

[8]

Outline four different functions of membrane proteins.

[4]

Distinguish between anabolism, catabolism and metabolism.

[3]

Markscheme

a. NAD/FAD carries/is reduced by gaining «two» H «atoms»/«two» electrons

b. reduced NAD produced in glycolysis/link reaction/Krebs cycle

c. reduced NAD/FAD delivers electrons/hydrogen «atoms» to ETC

d. ETC is in mitochondrial inner membrane/cristae

e. electrons release energy as they flow along the chain/from carrier to carrier

f. electrons from ETC accepted by oxygen/oxygen is the final electron acceptor

g. proteins in the inner mitochondrial membrane/electron carriers act as proton pumps

h. protons pumped into intermembrane space/proton gradient across inner mitochondrial membrane/proton concentration higher in intermembrane space than in matrix

i. energy «from electrons» used to pump protons into intermembrane space/generate a proton gradient / high H⁺ concentration is a store of «potential» energy

j. ATP synthase in inner mitochondrial membrane/cristae

k. energy released as protons pass down the gradient/through ATP synthase

l. ATP synthase converts ADP to ATP/phosphorylates ADP

m. oxidative phosphorylation «is ATP production using energy from oxidizing foods»

Accept H+ but not H/hydrogen in place of protons in any part of the answer.

Accept NADH or FADH in place of reduced NAD or FAD.

a. receptor/binding site for hormone/neurotransmitter

b. cell-to-cell communication / cell recognition

c. channels «for passive transport» / facilitated diffusion

d. pumps / active transport

e. cell adhesion

f. «immobilized» enzymes/enzymes embedded in the membrane