Question

Chlorophyll a is called universal photosynthetic pigment because it occurs in:
A) All photoautotrophs
B) All eukaryotic photoautotrophs
C) All oxygenic photoautotrophs
D) Both oxygenic and anoxygenic photoautotrophs

Answer 1

Hint: Chlorophyll is a green photosynthetic pigment found in algae, plants and cyanobacteria. Chlorophyll a is the main photosynthetic pigment.

Complete Answer:
There are four types of chlorophyll:
(I) Chlorophyll a it is found in all higher plants, algae and cyanobacteria.
(II) Chlorophyll b it is found in higher plants and green algae.
(III) Chlorophyll c is found in diatoms, dinoflagellates and brown algae.
(IV) Chlorophyll d is found only in red algae.

1) Chlorophyll a: It is bluish green or bright green pigment with a molecular formula $C_{55}​H_{72}​O_{5}​N_{4}​Mg$.
2) It is a universal photosynthetic pigment because it is present in every photosynthetic organism except eubacteria. It is a primary photosynthetic pigment. It is the most abundant photosynthetic pigment.
3) Chlorophyll a is directly involved in the light reaction of photosynthesis. It is present in the reaction centres of Photosystem I and Photosystem II.
4) Chlorophyll a is called the universal photosynthetic pigment as it is present in all oxygenic photoautotrophs except bacteria. It is present in many bacteria, archaebacteria, lower and higher plants and helps in photosynthesis.

Hence, the correct answer is option A (All photoautotrophs).

Additional information: The "photo" part of photosynthesis means the steps that convert solar energy to chemical energy, occurs in the chloroplast’s thylakoids. Water is split, providing a source of electrons and protons ($H^+$) and giving off $O_2$ as a by-product. Light absorbed transfers $e^-$ and $H^+$ to $NADP^+$, where they are temporarily stored. The light reduces $NADP^+$ to NADPH; it also generates ATP, using chemiosmosis to power the addition of a phosphate group to ADP (photophosphorylation).

Note: Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. It also reflects green-yellow light, and as such contributes to the observed green colour of most plants.