Assertion (A): The bacterial cell wall is composed of peptidoglycan. Reason (R): Peptidoglycan provides structural strength and prevents osmotic lysis. MCQ with Answer and Explanation

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.

Explanation:
Gastric Inhibitory Peptide (GIP), now more commonly called Glucose-dependent Insulinotropic Peptide, is an incretin hormone secreted by the K cells of the small intestine in response to the ingestion of food, particularly glucose and fats. Its name reflects its two main actions: 1) It inhibits gastric acid secretion and slows gastric emptying (the 'gastric inhibitory' effect). 2) In the presence of elevated blood glucose, it potently stimulates the beta cells of the pancreas to secrete insulin (the 'insulinotropic' effect), preparing the body to handle the incoming nutrients.

Explanation:
The double helix structure of DNA was elucidated by James Watson (an American biologist) and Francis Crick (a British physicist) in 1953 at the University of Cambridge. Their model was based on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins. They proposed that DNA consists of two antiparallel strands held together by hydrogen bonds between complementary base pairs (A-T, G-C).