The scientist who discovered the antibiotic streptomycin was: MCQ with Answer and Explanation

Explanation:
Cortisol (a glucocorticoid) from the adrenal cortex is a steroid hormone derived from cholesterol. Insulin and growth hormone are peptides, adrenaline is a catecholamine (amino acid derivative).

Explanation:
An action potential is initiated when a stimulus causes the membrane potential to reach a threshold. This opens voltage-gated sodium channels, leading to a rapid influx of sodium ions (Na+) into the neuron. This makes the inside of the cell positively charged relative to the outside, a process called depolarization. Repolarization follows with the efflux of K+ ions.

Explanation:
In plant tissue culture, when an explant (a piece of plant tissue) is placed on a nutrient medium containing specific plant hormones (like auxins and cytokinins), the cells dedifferentiate and undergo rapid, unorganized division to form a mass of cells called a callus. This callus is undifferentiated. Under appropriate hormonal conditions, this callus can then be induced to redifferentiate and form organized structures like shoots and roots (organogenesis) or somatic embryos.