Free Chemical Coordination And Integration (Daily Quiz: 3) NEET Biology Questions & Answers with Detailed Explanation & Full Review

Answer: (c)

Iodine is needed for the synthesis of $T_3$ and $T_4$ . Iodine binds to the tyrosine residues in thyroglobulin, which is then hydrolysed into iodothyronine that combine to form triiodothyronine ($T_3$ ) or thyroxine (tetra-iodothyronine or $T_4$ ). Therefore, deficiency of iodine in the diet of a pregnant female will lead to improper synthesis of thyroid hormones in newly borne infant. The deficiency of thyroid hormones in infants causes 'cretinism' whose symptoms are slow heartbeat, lower blood pressure, decrease in temperature, stunted growth, low intelligence quotient and abnormal skin.

Answer: (d)

Melatonin is a hormone that regulates the 24 hour rhythm of our body such as the sleep-wake cycle etc. Melatonin is produced by pineal gland in the brain, which is responsible for operation and regulation of the biological clock in mammals.

Answer: (b)

Insulin is a peptide hormone, secreted by the b cells of the islets of Langerhans in the pancreas, that promotes the uptake of glucose by body cells, particularly in the liver (hepatocytes) and muscles (adipocytes), and thereby controls its concentration in the blood.

Answer: (b)

Hormones thyroxine, adrenaline and the pigment melanin are formed from tyrosine. Tyrosine is transformed into dopa through the enzyme tyrosinase. Then through different metabolic pathways it produces thyroxine, adrenaline, melanin etc.