Consider statements about human respiration: 1. Hemoglobin has a higher affinity for CO2 than O2. 2. Carbonic anhydrase is present in RBCs. 3. Most CO2 is transported as bicarbonate. Which are correct? MCQ with Answer and Explanation

Explanation:
Glucagon, secreted by alpha cells of the pancreas when blood glucose is low, binds to liver receptors activating glycogenolysis (glycogen → glucose) and gluconeogenesis. Insulin promotes glycogenesis (glucose → glycogen). Thyroxine affects metabolism, somatostatin inhibits both insulin and glucagon.

Explanation:
The pineal gland is a small, pinecone-shaped gland located in the epithalamus, near the center of the brain. In humans, it is not a true eye, but it is photosensitive; it receives information about the light-dark cycle from the retina via the suprachiasmatic nucleus and the sympathetic nervous system, and uses this to regulate the secretion of melatonin, thus controlling circadian rhythms. In some lower vertebrates (like certain reptiles, amphibians, and fish), the pineal complex includes a parietal eye (or 'third eye'), a light-sensitive organ on the top of the head that can literally detect light and shadows, helping with camouflage and predator detection.

Explanation:
Photolysis of water occurs at the manganese cluster of photosystem II, releasing electrons, protons, and oxygen. The electrons replace those lost by P680. Photosystem I reduces NADP⁺. Cytochrome b6f transports electrons between the two photosystems. Thus, water splitting is a hallmark of PSII.