Chapter 11, Problem 1aCP

Compare the four chemical classes of hormones with reference to hormones within each class.

Summary Introduction

To review:

Comparison of four chemical classes of hormones.

Introduction-:

Hormones are the molecules that are produced and secreted into the bloodstream by endocrine glands. These molecules are then taken by the blood stream to target cells where they carry out their actions. Endocrine glands are derived from the epithelial tissues and are ductless unlike exocrine glands.

Explanation of Solution

Based on the difference in chemical structure, hormones have been classified into four major classes:

1. Amines: These hormones are derived from amino acids namely tyrosine and tryptophan. Examples are the hormones released by adrenal medulla, thyroid, and pineal glands.

2. Polypeptides and proteins: These hormones consist of polypeptide chains (chain of amino acids). If the polypeptide chain has less than 100 amino acids, it is called polypeptide. Example is oxytocin. But if it has more than 100 amino acids like in case of growth hormone, it is called proteins.

3. Glycoproteins: In this, protein molecule is attached to one or more carbohydrate groups. Examples are follicle stimulating hormones (FSH).

4. Steroids: These hormones are derived from cholesterol. An enzyme is responsible for cleaving off the side chain which is attached to five-carbon ‘D’ ring in cholesterol molecule to form steroid hormones. Examples are estradiol, testosterone, and progesterone.

Following is the comparison of four classes of hormones: