The deficiency disease 'pellagra' is caused by lack of: MCQ with Answer and Explanation

Explanation:
Phytoplankton, including cyanobacteria, diatoms, and dinoflagellates, are microscopic photosynthetic organisms that drift in oceans and freshwaters. They are primary producers responsible for about half of global oxygen production. Brown, red, and green macroalgae also contribute but phytoplankton are the primary oxygen producers.

Explanation:
The mucosal lining of the small intestine forms numerous finger-like projections called villi, which vastly increase the surface area for absorption of nutrients. Each villus contains a network of capillaries and a central lymphatic vessel (lacteal) for absorbing amino acids, sugars, and fats, respectively. Microvilli are further projections on the epithelial cells of the villi.

Explanation:
Carbohydrates are the main and most readily available source of energy for cellular processes. Proteins are polymers of amino acids linked by peptide bonds, not fatty acids, which are components of lipids. Vitamins are micronutrients required in very small (trace) quantities for normal metabolism, unlike macronutrients. Therefore, only statement 1 is correct.