Question

Differentiate between the following :

(i) Peptide linkage and Glycosidic linkage

(ii) Essential amino acids and Non-essential amino acids

Hint:

Peptide linkage is the -CO-NH- bond between amino acids, and glycosidic linkage is the C-O-C bond between sugars. Essential amino acids come only from food, while non-essential ones are made in the body.

Answer 1

Step 1: Understanding the Question:
We must give the main differences for two pairs of terms from biomolecules. Each pair carries one mark.

Step 2: Part (i) Peptide linkage and Glycosidic linkage.
Peptide linkage: it is the amide bond \( \mathrm{-CO-NH-} \) formed between the carboxyl group of one amino acid and the amino group of another. It joins amino acids in proteins and peptides.
Glycosidic linkage: it is the ether type bond \( \mathrm{C-O-C} \) formed between two monosaccharide units when an \( \mathrm{-OH} \) group of one unit reacts with the anomeric \( \mathrm{-OH} \) of the other. It joins sugar units in disaccharides and polysaccharides.

Step 3: Part (ii) Essential and Non-essential amino acids.
Essential amino acids: the body cannot make them, so they must come from the diet. Examples are valine, leucine and lysine.
Non-essential amino acids: the body can make them on its own, so they are not needed in the diet. Examples are glycine, alanine and glutamic acid.

Final Answer:
(i) Peptide linkage is an amide bond between amino acids; glycosidic linkage is a C-O-C bond between monosaccharides.
(ii) Essential amino acids must be taken in food; non-essential amino acids are made in the body.