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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]
a.

Outline four different functions of membrane proteins.

[4]
b.

Distinguish between anabolism, catabolism and metabolism.

[3]
c.

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.

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 

g. electron transport / electron carriers

b.

a. metabolism is all enzyme-catalyzed reactions in a cell/organism/is anabolism plus catabolism 

b. anabolism is synthesis of polymers/complex/larger molecules/larger substances «from smaller molecules/monomers» 

c. catabolism is breaking down «complex» molecules/substances «into simpler/smaller ones/into monomers»

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 1: Cell biology » 1.3 Membrane structure
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