Railway Science (Biology – Enzymes and Hormones)

Thyroxine (T4) - A type of thyroid hormone. It is the main hormone secreted into the bloodstream by the thyroid gland. It plays vital roles in metabolism, heart and muscle function, brain development, and maintenance of bones.
The production of thyroxine is hindered in the absence of iodine and leads to the condition known as Goitre.

It is a plant hormone that plays an important role in cell growth and development. Gibberellins help in the growth of different plant parts like stems. Cytokinins help in cell division and differentiation. Abscisic acid retards plant growth.

Auxins - Found in growing apices of roots and stems and then migrate to other parts to act. They prevent premature fall of leaves, flowers, and fruits and help in cell elongation of stems and roots. Phototropism is the ability of the plant to reorient the shoot growth towards a direction of light source.

Testosterone: It is found in both males and females but it is predominant in males. The changes related to puberty in the human body occur due to the secretion of testosterone in males and oestrogen in females.
Thyroxin: Secreted by the thyroid gland. Thyroxine regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxine.
Insulin: Hormone produced by the pancreas, helps in regulating blood sugar levels.

Pepsin is a stomach enzyme that serves to digest proteins found in ingested food. Amylase is an enzyme or special protein that helps to digest carbohydrates. Lipase is an enzyme that breaks down fats during digestion. Trypsin is an enzyme that aids with digestion.

It breaks down protein in the small intestine. It is produced by Pancreas in an inactive form called Trypsinogen. Pepsin : Secreted by - Gastric chief cells (found in stomach) in an inactive form called Pepsinogen.
Function - To digest proteins found in ingested food. Lipase : Secreted by - Pancreas. Function - Break down fats in food.
Amylase : Secreted by - Salivary glands and the Pancreas. Function - Digest starch into smaller molecules, yielding maltose.

Testosterone (androgens). Testes in males possess two kinds of cells : the sperm-producing germinal cells and the hormone-producing interstitial cells. Leydig cells of the testis are responsible for producing Testosterone.

There are three pairs of Salivary glands in our mouth cavity: i) Parotid glands, located in front of and below each ear; produces watery saliva rich in amylase, ii) Submaxillary glands close to inner side of lower jaw, produce water and mucus, iii) Sublingual glands below the tongue, produce water and mucus. These glands continuously pour saliva into the mouth cavity. The amount of saliva secreted is about 1000 to 1500 ml per day.

Iodine (Symbol I and atomic number 53). Deficiency of Iodine causes goitre. Iron: It's an important component of haemoglobin, the part of red blood cells that carries oxygen from the lungs to the body. Sodium: It helps in controlling blood pressure. Calcium is necessary for bone health, muscle function, and nerve transmission.

Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits etc. Cytokinins help overcome apical dominance.
In most higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance