Page 219 - NCERT Science Class 10 English Medium

We have seen in the chapter on ‘Life Processes’ that the food we eat is
digested by various enzymes in our body. Have you ever wondered why
the same enzyme does not break-down everything we eat? Enzymes are
specific in their action, specific enzymes are needed for the break-down
of a particular substance. That is why we will not get any energy if we
try to eat coal! Because of this, many human-made materials like plastics
will not be broken down by the action of bacteria or other saprophytes.
These materials will be acted upon by physical processes like heat and
pressure, but under the ambient conditions found in our environment,
these persist for a long time.
Substances that are broken down by biological processes are said
to be biodegradable. How many of the substances you buried were
biodegradable? Substances that are not broken down in this manner
are said to be non-biodegradable. These substances may be inert and
simply persist in the environment for a long time or may harm the various
members of the eco-system.

Activity 13.6
Activity 13.613.6
Activity 13.6
Activity
Activity 13.6
n Use the library or internet to find out more about biodegradable
and non-biodegradable substances.
n How long are various non-biodegradable substances expected to
last in our environment?
n These days, new types of plastics which are said to be biodegradable
are available. Find out more about such materials and whether
they do or do not harm the environment.

Q U E S T I O N S

Give any two ways in which non-biodegradable substances would affect ?
1. Why are some substances biodegradable and some non-biodegradable?
2. Give any two ways in which biodegradable substances would affect the
environment.
3.
the environment.

Visit any town or city, and we are sure to find heaps of garbage all over
the place. Visit any place of tourist interest and we are sure to find the
place littered with empty food wrappers. In the earlier classes we have
talked about this problem of dealing with the garbage that we generate. Let
us now look at the problem a bit more deeply.

214 Science

2024-25