Question

A specific function of light in the process of photosynthesis is to

• A. Activate chlorophyll.
• B. Split water.
• C. Synthesise glucose.
• D. Reduce CO${}_2$.

Answer 1

The correct option is A Activate chlorophyll.

A specific function of light in the process of photosynthesis is to activate chlorophyll. When light energy is absorbed by a chlorophyll molecule its electrons gain energy and move to higher energy levels in the molecule (photoexcitation). Sufficient energy ionizes the molecule, with the electron being 'freed' leaving a positively charged chlorophyll ion. This is called photoionization.

In whole chloroplasts, each chlorophyll molecule is associated with an electron acceptor and an electron donor. These three molecules make up the core of a photosystem. Two electrons from a photoionized chlorophyll molecule are transferred to the electron acceptor. The positively charged chlorophyll ion then takes a pair of electrons from a neighbouring electron donor such as water.

So, the correct answer is option A.