Question

define hormone.write the characteristic

Answer 1

Hormones are chemical messengers that help to control and coordinate various metabolic activities in the bodies
Eg thyroxine regulates rate of cellular metabolism
Growth hormone regulates growth

Answer 2

Hormones are the chemical substances which co-ordinate and control the activities of living organisms and also their growth.

Characteristics of Hormones:-
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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. 
They are secreted only when needed, they are not stored prior to requirement. 
Hormones may be proteinaceous or non-proteinaceous in nature (amino-acids or steroids). 
The secretion of hormones is regulated by the nervous system through the feed back effect. 
Hormones usually cause long term effects like change in behavior, growth, etc.
The hormones function is to stimulate or inhibit the target organs.