1.  What are nutrients?  

Nutrients are substances, such as proteins, carbohydrates, fats, minerals, etc. which an organism obtains from its surroundings and uses it either as an energy source or for synthesis of body constituents.

2.  What is nutrition?

Nutrition is a process of intake or synthesis of nutrients by an organism and their utilisation. 

3.  Why do we require the process of nutrition?

Living organisms require the process of nutrition for following
(i) Nutrients act as energy source for all life processes
(ii) Nutrients provide raw material for growth, development and repair of body.

4.  What are the two broad ways of obtaining nutrients?

Autotrophic and heterotrophic nutrition.

5.  Define the terms autotrophic nutrition

Autotrophic nutrition can be defined as a type of nutrition in which organisms (autotrophs) synthesise organic materials (carbohydrates) from an inorganic source (water, carbon dioxide, minerals, etc.).

6.  Give two examples of autotrophs.

Green plants and autotrophic bacteria.

7.  Define the term heterotrophic nutrition.

Heterotrophic nutrition can be defined as a type of nutrition in which energy is derived from the organic substances that are obtained from plants or animals. The organic substances are first digested into simple forms, then are utilised by the organism.

8.  Give any two examples of heterotrophs.

All animals, fungi and bacteria (non-autotrophic).

9.  What are enzymes?  What is their role in the body of an organism?

Enzymes are biological catalysts that help in biochemical reactions taking place in the cell.

10.  How are heterotrophs dependent on autotrophs?

Heterotrophs cannot synthesise complex organic material (food) themselves. Hence they are dependent directly or indirectly on autotrophs for their nutritional requirements. 

11. Differentiate between autotrophs and heterotrophs