The gland responsible for regulating circadian rhythms is the: MCQ with Answer and Explanation

Explanation:
Niacin is part of NAD⁺/NADH, which donates electrons to the electron transport chain to generate the proton gradient for ATP synthesis. All B vitamins contribute indirectly.

Explanation:
Prokaryotic cells (bacteria, archaea) are characterized by the absence of a true, membrane-bound nucleus; their genetic material is located in a nucleoid region. Eukaryotic cells (plants, animals, fungi, protists) possess a true nucleus and various membrane-bound organelles like mitochondria, ER, and Golgi. Plant cells are distinguished from animal cells by the presence of a rigid cell wall made primarily of cellulose, along with chloroplasts and a large central vacuole. Thus, statements 1 and 2 are correct.

Explanation:
Earthworms have hemoglobin dissolved in their blood plasma (not in cells) for oxygen transport. Hemocyanin is in mollusks and arthropods, hemerythrin in some marine worms.