Question

(a) Why is glycogen known as animal starch?

(b) Differentiate between essential amino acids and non-essential amino acids.

(c) What is the effect of denaturation on the structure of proteins?

Hint:

Glycogen is the branched storage polysaccharide of animals. Essential amino acids come only from food. Denaturation destroys secondary and tertiary structure but not primary structure.

Answer 1

Step 1: Glycogen as animal starch, part (a):
Starch is the stored form of carbohydrate in plants. It is a mix of amylose and amylopectin.
Glycogen has a structure similar to amylopectin, with branched chains of \( \alpha \)-D-glucose units. It is, however, more highly branched.
In animals, glycogen is stored in the liver and muscles, and it is broken down to glucose when energy is needed.
Because it plays the same storage role in animals that starch plays in plants, it is called animal starch.

Step 2: Essential and non-essential amino acids, part (b):
Essential amino acids cannot be made by the human body. They must be taken in through the diet. Examples: valine, leucine, lysine.
Non-essential amino acids can be made by the body, so they need not be supplied in food. Examples: glycine, alanine, glutamic acid.

Step 3: Effect of denaturation, part (c):
Denaturation happens when a protein is exposed to heat, a change in pH, or certain chemicals.
The hydrogen bonds that hold the secondary and tertiary structures break. The helix and the folded shape unwind.
The primary structure (the sequence of amino acids) stays the same, because the peptide bonds do not break.
The protein loses its biological activity. The coagulation of egg white on boiling is an example.

Final Answer:
Glycogen is the branched storage polysaccharide of animals, like starch in plants. Essential amino acids come from food, while non-essential ones are made in the body. Denaturation destroys the secondary and tertiary structures but keeps the primary structure.