Question 19N.2.HL.TZ0.b.ii
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.2.HL.TZ0.b.ii |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | b.ii | Adapted from | N/A |
During photosynthesis plants use water in the conversion of light energy to chemical energy.
Explain how water is used in photosynthesis.
[3]
a. water is split/broken «up»/lysed/undergoes photolysis ✔ For mpa, reject “water is cut in half”. For mpa, accept photolysis only if the context shows that water is being split.
b. producing/providing electrons ✔
c. replaces electrons lost by Photosystem II / PSII / P680 / chlorophyll a ✔ For mpc, do not accept just chlorophyll.
d. allows electrons «to continue» to pass along the electron transport chain ✔
e. provides protons/H+ «inside thylakoid» to help generate a «proton» gradient/maintain high concentration inside thylakoid ✔ For mpe, reject pumping of protons into the thylakoid as photolysis produces them inside the thylakoid.
