Which of the following statements about the human skeleton is correct? MCQ with Answer and Explanation

Explanation:
Vitamin C (ascorbic acid) is a cofactor for prolyl and lysyl hydroxylase enzymes that hydroxylate proline and lysine in collagen synthesis, necessary for stabilizing collagen triple helix. Deficiency leads to impaired collagen formation, causing scurvy—fragile blood vessels, bleeding gums, poor wound healing. Vitamin A is for vision, D for bone, K for clotting.

Explanation:
Chloroplasts are present only in the green, photosynthetic parts of plants, not in root cells or non-green tissues. Plant cells typically have a single, large central vacuole occupying most of the volume, whereas animal cells have small, temporary vacuoles. Centrioles are absent in higher plants (angiosperms and gymnosperms) but present in animal cells and some lower plants. Only statement 2 is correct.

Explanation:
Hemoglobin is an iron-containing metalloprotein in erythrocytes that binds oxygen reversibly, forming oxyhemoglobin. Each molecule has four heme groups, each binding one O₂. Collagen is a structural protein, insulin a hormone, fibrinogen a clotting protein. Hemoglobin also carries some CO₂ and buffers blood pH.