Explain the role of hydrogen ions used in photosynthesis.

Describe how the structure of the chloroplast is adapted to its function in photosynthesis.

The enzyme Rubisco is used in carbon fixation during photosynthesis. Identify four other examples of proteins that illustrate the wide range of functions of this group of biochemicals in living organisms.

a. hydrogen ions (and oxygen) are obtained from photolysis of water ✔

b. (excited) electrons (from Photosystem II) contribute to generate a hydrogen ion/proton gradient
OR
protons build up in the thylakoid space/inside the thylakoid ✔

c. ATP synthase generates ATP by chemiosmosis/using the proton gradient/by movement of protons from the thylakoid space to the stroma ✔

d. (two) high energy/excited electrons (from Photosystem II) are passed through an electron transport chain ✔

e. NADP accepts H⁺ (from the stroma) / electrons to produce NADPH⁺/reduced NADP ✔

f. ATP/reduced NADP/NADPH⁺ are used by light-independent reactions/Calvin cycle in the stroma ✔

g. (in Calvin cycle) carbon fixation to ribulose bisphosphate/RuBP produces G3P ✔

h. ATP is used to transform G3P to TP ✔

i. reduced NADP/NADPH⁺ is used to transform G3P to TP ✔

Accept answers in an annotated diagram.

Accept NADPH₂/NADPH/NADPH + H⁺ in place of NADPH⁺.

a. thylakoids have a small internal volume to maximize hydrogen gradient / quickly increase concentration gradient ✔

b. many grana / thylakoids give large surface area ✔

c. (grana) contain (photosynthetic) pigments/electron carriers/ATP synthase enzymes ✔

d. (photosynthetic) pigments/chlorophyll arranged into photosystems allowing maximum absorption of light energy ✔

e. stroma has suitable pH/ enzymes of Calvin/light independent cycle ✔

f. lamellae connect/separate grana maximizing photosynthetic efficiency ✔

Accept diagram showing the disposition in space.

a. insulin receptors start the cellular signalling pathway/other receptor

b. leptin is a hormone / other protein hormone ✔

c. immunoglobulins/antibodies defend body from disease ✔

d. rhodopsin/photosystems convert light energy to electrical impulses ✔

e. keratin/collagen/other example is a structural protein ✔

f. tubulin/microtubules part of cytoskeleton/ involved in cell division

g. ATP synthase is an enzyme that catalyzes the formation of ATP / other enzyme and function ✔

h. fibrin/fibrinogen is a protein involved in clotting ✔

i. hemoglobin/sodium potassium pump/other example is a transport protein ✔

j. actin/myosin/other example is involved in muscle contraction ✔

k. any other named example and function ✔

l. a second other named example and function ✔

m. spider silk is used to form spider webs/capture prey ✔

Accept only one example of each protein type for example only one enzyme or only one hormone etc. 

Mp k can be awarded only once.

Mp I can be awarded only once.

Question 6 was a popular question.

A relatively high scoring section, though many students failed to discuss the role of hydrogen in the light independent reactions.

Question 6 was a popular question.

Well answered.

Question 6 was a popular question.

Well answered by most except for when students gave multiple examples of proteins of the same functional type; for example, four examples of enzymes when the question asked for an illustration of the wide range of functions of proteins.