Life Process

If an organism is alive, it must keep repairing and maintaining its structures. The maintenance functions of living organisms must go on even when they are not doing anything particular. The processes which together perform this maintenance job are called life processes.

The branch of biology that deals with the study of life processes or vital activities is called physiology.

To maintain various life processes and to prevent damage and breakdown, energy is required. Energy is taken from the food (complex organic matter).

The process which involves taking of food inside the body and utilizing it for various activities is called nutrition.

The digested food and inhaled oxygen are transported to every cell of the body through blood by the circulatory system, this process is called transportation.

The oxidation of food takes place inside every cell of the body by a process called respiration. In respiration, energy is generated and waste products are formed. These waste products are required to be removed from the body by a process called excretion.

• In unicellular organisms (like Amoeba), all the life processes take place through the entire surface of cell because it is in direct contact with the environment.

• In multicellular organisms, all the cells may not be in direct contact with the surrounding environment, so they require specific organs for performing all the life processes. 

1.0How does life on the Earth depend on carbon-based molecules?

Life on the earth depends on carbon-based molecules because food is essential for life and food is made of carbon-based molecules like carbohydrates, fats and proteins. Carbohydrates and fats provide energy and proteins are required for body building, repair and maintenance.

2.0Criteria to decide whether something is alive

Living beings give response to stimuli and they show movement which may be visible (locomotion or movement of body parts) and invisible (at the molecular level). For example, organization of cells into tissues, tissues into organs and organs into organ system, all are dependent upon the movement of molecules. Therefore, molecular movement is basic to living beings.

Living beings can respire, grow, reproduce and they have ability to evolve.

All living beings have definite shape, size, life span and they perform metabolic activities. 

3.0Why is molecular movement absent in virus when it is outside the host cell?

Outside the living cells, virus behaves as non-living. It does not exhibit any life process and any molecular movement. But when it enters inside living cell it takes over the metabolic machinery of the host cell for the synthesis of its proteins, multiplication of genetic material that have all information necessary to produce new viruses.

There are mainly four important life processes which are required for maintaining life, without which living beings cannot survive.

1. Nutrition (for obtaining nutrients)

2. Respiration (for releasing energy)

3. Transportation (for distribution of food and other materials)

4. Excretion (for removal of toxic wastes)

All these life processes take place only in living organisms.

Nutrition

“Nutrition is the process of procuring and utilization of food.”

All living organisms require energy and other raw materials for performing all the vital activities and for body building, repair, growth, development and regulation. Both energy and raw materials are obtained from the food. Food is the combination of organic and inorganic substances. It provides energy and nutritional support to our body. 

Nutrients are the organic or inorganic substances required for the maintenance of life and survival of living organisms.

The food taken in by an organism contains a large number of nutrients like carbohydrates, fats, proteins, minerals, vitamins and water.

Carbohydrates and fats provide energy. Proteins are required for body building, growth and healing. Vitamins and minerals are the regulating nutrients.

Respiration

“The process of releasing energy from food is called Respiration”.

Most living beings need oxygen (of air) to obtain energy from food. This oxygen reacts with the food molecules (like glucose) present in the body cell and burns them slowly to release energy. The energy thus released is stored in ATP molecules in the cells. The body can use this stored energy whenever it wants to do so.

Respiration is the process by which the food taken through nutrition gets oxidized to release energy for various activities.

Respiratory substrates are the organic compounds which are used in respiration to provide energy. Most common respiratory substrate is glucose.

Transportation

“Transportation whether in plants or animals is the key to the efficient assimilation of the nutrients that the organisms synthesize, get from their environment or digest.”

In unicellular organisms, a single cell carries out all the life processes as the cell itself is the organism. In advanced forms like the few-celled algae, protozoa, sponges, etc., the size of the organism ensures that all the cells are not very far from each other. The uptake of materials from the environment is through the general body surface and the transport within the cells is by diffusion. However, more advanced multicellular forms need a transportation mechanism. The sites of absorption and synthesis are very specific and are separated by a greater distance from the other parts of the body.

The actual movement of materials into the individual cells is by diffusion, osmosis or active transport.

The heart of a healthy man beats normally 72 - 80 per minute.

Excretion

“The biological process of removal of harmful nitrogenous wastes from the body is called excretion.”

Metabolic reactions occurring in animal body produce certain nitrogen-containing materials which are of no use in the cells. These are called nitrogenous waste materials. They are formed from breakdown of proteins and nucleic acids. They become toxic if allowed to accumulate in the body. Therefore, these materials must be removed from the body for healthy life. The elimination of nitrogenous waste products from the animal body to regulate the composition of the body fluids and tissues is called excretion.

Various metabolic activities generate nitrogenous materials which need to be removed. It is an essential process in all forms of life.

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