Question

Glycogen is:
A) A polymer of $\beta - D - glucose$ units
B) A structural disaccharide
C) Structurally very much similar to amylopectin
D) Structurally similar to amylopectin but extensively branched.

Answer 1

The glucose stored in our body is made from many connecting units of glucose and this form is known as glycogen. When the body requires energy, glycogen breaks down into glucose units to provide that energy.

Complete answer:
Let us first understand the function and structure of glycogen. Glycogen is a polysaccharide of glucose. It functions as an energy storage unit in the human body.
Now let us check whether the given options are true.
A) Glycogen is formed by the branched polymerization of glucose. Glycogen is made of $\alpha - D - glucose$ monomers so option A is not true.
B) Glycogen is a polymer and a polysaccharide of glucose. Hence it is not a disaccharide. Therefore, option B is not true.
C) Let us first draw the structure of glycogen. It is given as follows.

This polymeric structure of glycogen is similar to the structure of amylopectin. But the structure of glycogen is heavily branched when compared to amylopectin. Hence, option C is not completely true.
D) Glycogen and amylopectin have similar structures but glycogen is heavily branched or extensively branched.

Hence, option (D) is correct.

Note: It is to be noted that amylopectin is a polysaccharide of glucose and is mostly found in plants. Amylopectin and amylose both form starch. In amylopectin glucose molecules are linked in a linear fashion whereas in glycogen they are linked in branched manner.