The pigment that absorbs light energy in the photosystems of plants is:
A. Phytochrome
B. Xanthophyll
C. Chlorophyll a
D. Carotene
Answer: Option C
Solution (By JKExamLibrary)
Chlorophyll a is the primary photosynthetic pigment that acts as the reaction center in photosystem I (P700) and II (P680), converting light energy to chemical energy. Accessory pigments like chlorophyll b, carotenes, and xanthophylls absorb light and transfer energy to chlorophyll a. Phytochrome is involved in photoperiodism. Without chlorophyll a, photosynthesis cannot occur.
Explanation:
Riboflavin (vitamin Bâ‚‚) is the precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are electron carriers in redox reactions. Thiamine is TPP, niacin NAD/NADP, pantothenic acid CoA.
Explanation:
Neurotensin is a 13-amino acid peptide that functions as both a neuromodulator in the central nervous system and a hormone in the gastrointestinal tract. In the gut, it is secreted by the N cells in the ileum in response to fat ingestion. Its primary gastrointestinal functions are to inhibit gastric motility and gastric acid secretion (contributing to the 'ileal brake'), and to stimulate the release of histamine from mast cells and glucagon from the pancreas. It also causes vasodilation in the intestinal mucosa.
Consider statements about human skin: 1. The epidermis is the outermost layer. 2. Sweat glands help in thermoregulation. 3. Melanin protects against UV radiation. Which are correct?
Explanation:
The skin consists of the outer epidermis and the inner dermis. The epidermis contains melanocytes that produce melanin, a pigment that absorbs harmful ultraviolet radiation, protecting deeper tissues. Sweat glands in the dermis secrete sweat onto the skin surface; its evaporation removes heat, playing a crucial role in body thermoregulation. All statements are correct.
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