Question

The molecular weight of chlorophyll a is
A. 907
B. 893
C. 911
D. 712

Answer 1

Chlorophyll is the green photosynthetic pigment that is known for carrying out the process of photosynthesis. There are four types of chlorophyll molecules: chlorophyll a, b, c, and d.

Complete answer:
Chlorophyll a is used in oxygenic photosynthesis. The chemical formula of chlorophyll a molecule is ${C_{55}}{H_{72}}Mg{N_4}{O_5}$. Hence, its molecular weight is about 893.509 g/mol. It is found in all higher plants, algae, and cyanobacteria. It absorbs the light in violet, red and blue wavelengths while mainly reflecting the green light. Thus, this reflecting light is known for giving chlorophyll a molecule its green color.
In the case of chlorophyll b molecules, the chemical formula is ${C_{55}}{H_{72}}Mg{N_4}{O_6}$. Hence, the molecular weight of chlorophyll b molecules is about 907.5 g/mol. It is known to be found in green algae and higher plants. This molecule absorbs red-blue light and reflects green light. So, option (A) is incorrect.
Option (C) and (D) are also incorrect because the molecular weight of chlorophyll a is about 893.509 g/mol, which is not even close to 911 or 712 g/mol.

Hence, the correct option is (B).

Additional information:
The word chlorophyll has been derived from two Greek words, ‘chloros’ meaning green, and ‘phyllon’ meaning leaf. All four types of chlorophyll molecules have the same chemical structure composed of chlorine rings and the difference lies in the chemical groups that are attached to the chlorin ring. Chlorophyll c is present in various types of algae while chlorophyll d is present in red algae.

Note: Chlorophyll a molecule is present in higher plants, algae, and cyanobacteria that is known for carrying out oxygenic photosynthesis. Its molecular weight is about 893.509 g/mol.