STPM Biology Biological Molecules Part 12 Lipid - Steroids

1. Steroid is very different in structure compared to lipid but is classified together with lipid because of their similar nature.

2. Steroid are abundant in animal tissues, but it is hardly found in plants.

3. All steroid molecules consist of four fused rings of carbon atoms. Different steroids have different functional groups attached to this ensemble of rings.

The typical steroid structure with 17 carbon atoms

4. The most common steroid in the body is cholesterol. Many steroid hormones are produced from cholesterol.

5. Other examples are vitamin D2 (calcipherol), bile acids, sex hormones (testosterone, progesterone and oestrogen), and adrenaline.

Examples of steroids

6. Cholesterol is synthesized in the liver. The importance of cholesterol in health:

• Cholesterol is important in the health of cell membrane. It is a major component in the cell membranes of animals.
• Cholesterol is a precursor for synthesizing animal hormones such as progesterone, bile acids, oestrogen, and others. These hormones are important for the healthy functioning of organisms.
• Used to synthesize vitamin D in the skin.
• Excess cholesterol in the body can lead to arteriosclerosis, high blood pressure and heart attacks.

Arteriosclerosis