The antibiotic penicillin is obtained from: MCQ with Answer and Explanation

Explanation:
Primary lymphoid organs are where lymphocytes are produced and mature. Bone marrow (where B cells mature) and thymus (where T cells mature) are primary. Secondary lymphoid organs, like spleen, lymph nodes, and tonsils, are where mature lymphocytes encounter antigens and initiate immune responses. The bone marrow also is the site of hematopoiesis.

Explanation:
Bacterial cell walls contain peptidoglycan (murein), a unique polymer that maintains cell shape and protects against osmotic pressure. The reason correctly explains why peptidoglycan is essential.

Explanation:
Pepsin is the main digestive enzyme in the stomach. It is secreted by the chief cells (zymogenic cells) of the gastric glands in an inactive form called pepsinogen. Pepsinogen is activated into pepsin by the acidic environment created by hydrochloric acid (HCl) secreted by parietal cells. Pepsin then digests proteins into proteoses and peptones.