Question

Floridean starch as stored photosynthate is present in
A.Chlorophyceae
B.Xanthophyceae
C.Phaeophyceae
D.Rhodophyceae

Answer 1

Hint: 1.Floridean starch is a storage unit of carbohydrates.
2.It has a structure similar to amylopectin and glycogen.

Complete answer:
Floridean starch is a primary sink of carbohydrate from photosynthesis. It is a form of storing food in certain algae.They are found in the cytoplasm outside the chloroplast of the cell,as small granules.They occur in the form of a cap over pyrenoid.SImilar to the structure of amylopectin and glycogen, it consists of α-linked glucose polymer. This is a highly branched molecule. The degree of branching of this polymer is more similar to amylopectin. Hence they are sometimes called semi amylopectin. The difference in branching and frequency of glucose polymers lead to their different physical properties,when compared to other compounds of similar function. Now let's analyse the options to find out the correct answer.
Option A) Chlorophyceae is also known as green algae. In them carbohydrates are stored in the form of starch. It consists of amylose and amylopectin. Therefore this is an incorrect option.
Option B) In xanthophyceae which are also known as yellow-green algae starch and pyrenoids are not formed. Instead food is stored in the form of oil globules. So they don’t contain floridean starch. Therefore this is an incorrect option.
Option C) Phaeophyceae is also known as brown algae. In these algae stored food is found in the form of mannitol. So they don’t contain floridean starch. Therefore this is an incorrect option.
Option D) Rhodophyceae is also known as red algae and food reserves are found in them in the form of floridean starch. Therefore this is the correct option.

Hence, the correct answer is option (D).

Note: Amylose that makes up starch is usually absent in floridean starch. Building blocks of this compound are called UDP-glucose with alpha(1,4) linkage primarily and occasionally branched from alpha(1,6) linkage.