Assertion (A): Bacteria can be killed by antibiotics like penicillin. Reason (R): Penicillin inhibits the synthesis of bacterial cell wall. MCQ with Answer and Explanation

Explanation:
Calcitonin, secreted by parafollicular (C) cells of the thyroid, decreases blood calcium by inhibiting osteoclasts and promoting calcium deposition in bones. Parathyroid hormone (PTH) raises calcium.

Explanation:
The small intestine is highly specialized for absorption, with circular folds, villi, and microvilli massively increasing its surface area. The duodenum is the first, shortest part, receiving the hepatopancreatic duct carrying bile and pancreatic juice. The ileum is the third and final part, connecting to the large intestine. Thus, statements 1 and 2 are correct.

Explanation:
Ion exchange chromatography separates proteins based on their net surface charge; positively charged proteins bind to cation exchangers, negatively to anion exchangers. Gel filtration separates by size, affinity by specific binding, SDS-PAGE by molecular weight.