Introduction

Health is a state of complete physical, mental and social well-being.

Basic conditions for good health:

• Proper balanced and nutritious diet.
• Personal hygiene.
• Clean environment and surroundings.
• Healthy air, no pollution in the surrounding.
• Regular exercise.
• Proper rest.
• Good standard of living and economy status.

We know that cells are the basic units of living beings. Cells are made of a variety of chemical substances- proteins , carbohydrates , fats or lipids and so on. Cells move from place to place. Even in cells that do not move, there is repair going on. New cells are being made. In our organs or tissues, there are various specialised activities going on- the heart is beating, the lungs are breathing, the kidney is filtering urine, the brain is thinking.

All these activities are interconnected. For all these interconnected activities, energy and raw material are needed from outside the body.