Staying Alive – How Living Systems Live

The Basic Unit of Life – The Cell

All living things are made up of cells. All cells are “alive” – they live, breathe, reproduce, excrete and die. They take in food. They produce new cells through division. They get rid of waste. Often, they may get damaged and need to repair themselves. They also maintain a set of stable conditions for the body inside which they reside – conditions such as temperature, pressure, water content and so on. Where do they get the food from for all this?

There are three main classes of food –

1. Carbohydrates
2. Proteins
3. Fats

Animals get Protein from the foods they eat. Plants build protein from nutrients in soil and air. Human body cells are largely made up of protein. Cells manufacture protein from special chemicals known as amino acids. Each protein has a specific function. Some are used to create new cells. Some, known as enzymes, help in the process of digestion. Some, known as antibodies, help ward off infection and disease. Some, known as hormones, maintain the conditions of the body. And so on.

Homeostasis

Living organisms need to maintain a stable set of conditions in their bodies. This is referred to as Homeostasis. The living organism reacts to various external environmental factors and makes internal adjustments, known as reflexes. For example, on a hot day, the reflex is to allow the body to sweat more. Or while climbing a hill the reflex is to increase blood circulation to the muscles. All these and many more internal processes such as the nervous system, respiratory system, excretory system, and so on are maintained in this manner.

Check Point

1. The following are functions of cells –
   1. Taking in food
   2. Creating new cells
   3. Maintaining Homeostasis
   4. All of the Above
2. Enzymes, hormones, and antibodies all are forms of ______.
3. The main function of adipose tissue is to store –
   1. Carbohydrates
   2. Fats
   3. Proteins
4. Carbohydrates are broken down into ______ by the digestive system.
5. Maintaining stable conditions in a body is a process known as ______.

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