Which disease is caused by the bacterium Salmonella typhi? MCQ with Answer and Explanation

Explanation:
In 1953, Stanley Miller and Harold Urey conducted an experiment to test the Oparin-Haldane hypothesis of chemical evolution. They simulated the reducing atmosphere of primitive Earth, which they believed lacked free oxygen. The gas mixture used was methane (CH4), ammonia (NH3), hydrogen (H2), and water vapor (H2O). By applying electrical sparks (simulating lightning), they successfully synthesized amino acids and other organic compounds.

Explanation:
Beriberi results from lack of thiamine (B₁), affecting the nervous and cardiovascular systems. It manifests as dry beriberi (peripheral neuropathy) or wet beriberi (heart failure). Pellagra is niacin deficiency, scurvy vitamin C, rickets vitamin D. Thiamine is a coenzyme in carbohydrate metabolism.

Explanation:
During fertilization, when a capacitated sperm penetrates the outer layer of cumulus cells (corona radiata) and makes contact with the glycoprotein layer called the zona pellucida of the secondary oocyte, it triggers the acrosome reaction. The acrosome (a cap-like vesicle over the sperm head) releases hydrolytic enzymes (like acrosin) that digest a path through the zona pellucida, allowing the sperm to reach and fuse with the oocyte's plasma membrane.