Question

Fucoxanthin occurs in:
A. Cyanophyceae
B. Rhodophyceae
C. Chlorophyceae
D. Phaeophyceae

Answer 1

The xanthophyll fucoxanthin has the formula: ${C_{42}}{H_{58}}{O_6}$. Blue algae and most other heterokonts have it as an accessory pigment in their chloroplasts, giving them a brown or olive-green appearance. Fucoxanthin is a xanthophyll that accounts for more than $10\%$ of the total amount of carotenoids produced in nature. It's an accessory pigment present in the chloroplasts of brown macroalgae like Fucus spp. and golden-brown unicellular microalgae like diatoms.

Complete answer:
Option A: Cyanophyceae (blue-green algae) are algal-like bacteria that can contaminate surface water sources, particularly during the summer months. Microcystin is the poisonous ingredient that gives the water a mouldy flavor.
So, option A is incorrect.
Option B: Because of the predominance of the red pigment r-phycoerythrin in their bodies, Rhodophyceae members are generally referred to as red algae. The food is processed as floridean starch, which has a composition that is somewhat similar to amylopectin and glycogen. Flagellated cells aren't present at all.
So, Option B is incorrect.
Option C: The Chlorophyceae are a group of green algae that are characterized primarily by their ultrastructural morphology. Food can be stored in the form of oil droplets by certain algae. The cell wall of green algae is made up of two layers: an inner cellulose layer and an outside pentose layer.
So, option C is incorrect.
Option D: Members of the Phaeophyceae family are dark algae with a lot of yellowish-brown pigments called xanthophylls. They are usually multicellular, aquatic, and macroscopic in nature. They have pyriform motile reproductive cells with two flagella inserted laterally, one of which is tinsel style. Laminarin and mannitol are the reserve nutritional materials. 'Phaeophyceae' is the right response.
So, option D is the correct answer.

So, Option D is the correct answer.

Note:
Fucoxanthin, a marine carotenoid present in edible brown seaweeds, is a natural compound that may help people avoid obesity and type $2$ diabetes. Fucoxanthin's antiobesity activity is mostly due to an increase in energy consumption. Fucoxanthin is present in brown seaweeds, diatoms, and dinoflagellates, and has a special structure that includes an allenic bond, an epoxide, and a conjugated carbonyl group in the polyene chain, distinguishing it from plant carotenoids including - carotene and lutein.