The disease caused by the deficiency of vitamin B₃ (niacin) is characterized by: MCQ with Answer and Explanation

Explanation:
The plant cell wall is primarily made up of cellulose, hemicellulose, pectins, and proteins. Cellulose provides the main structural framework, while hemicellulose and pectins help in cross-linking and providing flexibility. Chitin is found in fungal cell walls, and peptidoglycan is found in bacterial cell walls.

Explanation:
The variable (V) region at the tips of the antibody Y-shape contains the antigen-binding site, which is specific to a particular antigen. The constant region determines the class (IgG, IgM, etc.) and effector functions. The Fc region binds to immune cell receptors. Variability in the V region is generated by gene rearrangement, allowing immense antibody diversity.

Explanation:
Essential amino acids are those that the human body cannot synthesize in sufficient quantities and must be obtained through the diet. There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Glycine, alanine, and serine are non-essential amino acids that the body can produce.