Who was the first scientist to observe bacteria using a single-lens microscope? MCQ with Answer and Explanation

Explanation:
Vitamin B₁₂ contains a cobalt ion at the center of its corrin ring structure, hence the name cobalamin. It is essential for DNA synthesis and nervous system function. Iron is in heme, magnesium in chlorophyll, zinc in many enzymes. B₁₂ is unique in having a metal-carbon bond.

Explanation:
Greenhouse gases trap heat in the Earth's atmosphere, contributing to the greenhouse effect and global warming. Carbon dioxide (CO2) and methane (CH4) are potent greenhouse gases emitted through human activities like fossil fuel combustion and agriculture. Oxygen (O2) and nitrogen (N2), which make up the majority of the atmosphere, are not greenhouse gases as they do not absorb infrared radiation. Thus, statements 1 and 2 are correct.

Explanation:
Bile is continuously synthesized by hepatocytes in the liver. It contains bile salts, bile pigments, cholesterol, and phospholipids. The gall bladder merely stores and concentrates bile, releasing it upon eating. The pancreas produces digestive enzymes, duodenum is part of the small intestine. Bile emulsifies fats.