IB Biology HL C1.3.11 Hl Photolysis of Water Questions

Follow photolysis at Photosystem II: light energy splits water, supplying electrons and protons while releasing oxygen in IB Biology HL C1.3.11.

Exam points

Describe photolysis as the light-driven splitting of water at Photosystem II to produce electrons, protons and oxygen.
Explain how photolysis products contribute to the light-dependent reactions: electrons replace those lost from Photosystem II, protons contribute to the thylakoid gradient, and oxygen is released.

[Maximum number: 3]

During photosynthesis plants use water in the conversion of light energy to chemical energy.

Explain how water is used in photosynthesis.

a. water is split/broken «up»/lysed/undergoes photolysis

b. producing/providing electrons

c. replaces electrons lost by Photosystem II / PSII / P680 / chlorophyll a

d. allows electrons «to continue» to pass along the electron transport chain

e. provides protons/ $\mathrm{H}^{+}$ «inside thylakoid» to help generate a «proton» gradient/maintain high concentration inside thylakoid

Marking guidance:
For mpa, reject “water is cut in half”.
For mpa, accept photolysis only if the context shows that water is being split.
For mpc, do not accept just chlorophyll.
For mpe, reject pumping of protons into the thylakoid as photolysis produces them inside the thylakoid.

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IB Biology HL C1.3.11 Hl Photolysis of Water Questions question 1