Question

define hormones.write its four characteristics

Answer 1

hormone (from the Greek participle “ὁρμῶ”, "to set in motion, urge on") is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour. Hormones have diverse chemical structures, mainly of 3 classes: eicosanoids, steroids, and amino acid/protein derivatives (amines, peptides, and proteins). The glands that secrete hormones comprise the endocrine signaling system. The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell (autocrine or intracrine signalling) or nearby cells (paracrine signalling).

Hormones are used to communicate between organs and tissues for physiologicalregulation and behavioral activities, such as digestion, metabolism, respiration, tissuefunction, sensory perception, sleep, excretion, lactation, stress, growth and development, movement, reproduction, and mood.[1][2]Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a signal transduction pathway. This may lead to cell type-specific responses that include rapid non-genomic effects or slower genomic[disambiguation needed] responses where the hormones acting through their receptors activate gene transcription resulting in increased expression of target proteins. Amino acid–based hormones (amines and peptide or protein hormones) are water-soluble and act on the surface of target cells via second messengers; steroid hormones, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmicand nuclear) to act within their nuclei.

Answer 2

hormone:-a regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.
General characteristics of hormones are as follows:

Hormones are secreted by endocrine cells.

Hormones are chemical messengers.

The are chemical signals that circulate in the body fluids.

The hormones regulate the behavior of the target cells.

Hormones, unlike enzymes do not catalyze any reaction.