Hormones and their functions:- pituitary, pineal, thyroid,pancreas gland and adrenal gland and osmoregulation in fishes and amphibians and mechanism of enzyme action?

Hormones and their functions:

1. Pituitary gland: The pituitary gland produces several hormones that regulate various bodily functions. Some of its key hormones include:

- Growth hormone (GH): Stimulates growth and development of bones and tissues.
- Prolactin: Stimulates milk production in females.
- Thyroid-stimulating hormone (TSH): Controls the release of hormones from the thyroid gland.
- Adrenocorticotropic hormone (ACTH): Stimulates the release of cortisol from the adrenal glands.
- Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): Regulate reproductive functions such as egg and sperm production.

2. Pineal gland: The pineal gland produces melatonin, a hormone that regulates sleep-wake cycles (circadian rhythm) and plays a role in the regulation of reproductive hormones.

3. Thyroid gland: The thyroid gland produces hormones that regulate metabolism, growth, and development. The main hormones produced by the thyroid gland are:

- Thyroxine (T4) and triiodothyronine (T3): Regulate metabolism, body temperature, and energy production.
- Calcitonin: Regulates calcium levels in the blood.

4. Pancreas gland: The pancreas gland produces hormones involved in the regulation of blood sugar levels. The main hormones produced by the pancreas are:

- Insulin: Lowers blood sugar levels by promoting the uptake of glucose by cells.
- Glucagon: Raises blood sugar levels by stimulating the release of stored glucose from the liver.

5. Adrenal gland: The adrenal glands produce hormones that help the body respond to stress and regulate various physiological processes. The main hormones produced by the adrenal glands are:

- Cortisol: Regulates metabolism, immune response, and stress response.
- Adrenaline (epinephrine) and noradrenaline (norepinephrine): Involved in the "fight or flight" response, increasing heart rate, blood pressure, and energy availability.

Osmoregulation in fishes and amphibians:
Fishes and amphibians live in aquatic environments and need to maintain proper water and salt balance in their bodies. Osmoregulation is the process by which they regulate the concentration of water and solutes in their body fluids.

Fishes: Most fishes are osmoregulators, meaning they actively regulate their internal salt and water balance. They have specialized structures like gills and kidneys to excrete excess water and retain essential ions. Freshwater fishes actively take in water through their gills and excrete dilute urine to eliminate excess water. Saltwater fishes, on the other hand, drink seawater and excrete excess salt through their gills and kidneys while conserving water.

Amphibians: Amphibians have permeable skin that allows for the exchange of water and ions with their environment. They are capable of both osmoregulation and osmoconformation. Osmoregulation involves actively regulating their internal salt and water balance, while osmoconformation involves adjusting their internal fluids to match the external environment. Amphibians living in freshwater environments excrete dilute urine and actively take in water through their skin. Those living in saltwater environments excrete excess salt through specialized glands.

Mechanism of enzyme action:
Enzymes are biological catalysts that speed up chemical reactions in living organisms. The mechanism of enzyme action involves several steps:

1. Substrate binding: The substrate, which is the molecule that the enzyme acts upon, binds to the active site of the enzyme. The active site is a specific region on the enzyme that complements the shape and chemical properties of the substrate.

2. Formation of enzyme-substrate complex: The enzyme and substrate form a temporary complex called the enzyme-substrate complex. This complex allows the enzyme to catalyze the conversion of the substrate into the product.

3. Catalysis: The enzyme catalyzes the conversion of the substrate into the product by lowering the activation energy required for the reaction to occur. This is achieved through various mechanisms, such as bringing the substrates closer together, providing a favorable microenvironment, or directly participating in the reaction.

4. Product formation and release: The enzyme facilitates the conversion of the substrate into the product. Once the reaction is complete, the product is released from the active site, and the enzyme is free to bind to another substrate molecule and repeat the process.

It is important to note that enzymes are highly specific, meaning they can only catalyze specific reactions with specific substrates. This specificity is determined by the shape and chemical properties of the active site.