Molecular movement is essential for life. It allows for the movement of oxygen, carbon dioxide, nutrients, and waste in and out of organisms. While viruses do not exhibit molecular movement outside their host cells, making them non-living, they can infect cells and behave as living entities. Multicellular organisms require specialized organ systems for processes like respiration and excretion because simple diffusion is not sufficient to meet the needs of all cells given their complexity. Key life processes in organisms include nutrition to intake energy sources, respiration to break down food, and excretion to remove waste products.

2. IS INVISIBLE MOVEMENTS OF MOLECULES (MOLECULAR MOVEMENT)
NECESSARY FOR LIFE?
MOLECULAR MOVEMENT IS DEFINITELY ESSENTIAL OR NECESSARY FOR
LIFE. FOR EXAMPLE MOVEMENT OF OXYGEN, CARBON DIOXIDE, WATER,
GLUCOSE, NITROGENOUS SUBSTANCES, PROTEINS, VITAMINS, MINERALS
ETC. IN THE BODY OF ORGANISMS.
VIRUSES DON'T SHOW ANY MOLECULAR MOVEMENT OUT OF THE HOST
CELLS. THEY ARE NONLIVING ENTITY OUT OF THE HOST. THEY CAN BE
CRYSTALLIZED.
THEY ONLY BEHAVE AS A LIVING BEING WHEN THEY INFECT A CELL.
THAT IS WHY, VIRUSES ARE ALSO KNOWN AS A CONNECTIVE LINK
BETWEEN LIVING AND NONLIVING THINGS.

3. WHY ARE MOLECULAR MOVEMENT NEEDED FOR LIFE?

4. WHAT ARE THE MAINTENANCE PROCESSES IN LIVING ORGANISMS?
WHAT ARE LIFE PROCESSES?

5. Nutrition: The energy comes from outside the body of the
individual organisms. The source of energy is transferred from
outside of the body of the organisms to the inside through the
process called nutrition. Nutrition is the mode of taking food. The
mode of Nutrition is divided into two main categories such as
autotrophic mode of nutrition e.g. plants) and heterotrophic
mode of nutrition (e.g. animals).
Since life on the earth depends on carbon based molecules most
of these food sources are also carbon based.

6. Oxidising - reducing reactions are some of the most common
chemical means to break down molecules.
For the breakdown of food sources, oxygen is required from the
outside of body.
Respiration: The process of the breakdown of source of energy (food)
(in presence or absence of oxygen) is known as respiration.
If the breakdown of source of energy takes place in absence of oxygen
it is known as anaerobic respiration. Less energy is released in this
process. (In yeast).
If the breakdown of source of energy takes place in presence of
oxygen, it is known as aerobic respiration. More energy is released in
this process.(In most of the organisms)

7. In case of single celled organisms no specific organs for taking in
food, exchange of gases or removal of wastes may be needed because
the entire surface of the organism is in direct contact with the
environment.
But in case of multicellular organisms all the cells may not be in
direct contact with the surrounding environment. Thus, simple diffusion
will not meet the requirement of all the cells. Hence, the multicellular
organisms need special organ system to perform these life processes.
Such as transportation system, excretory system, digestive system etc.
Note: All the basic materials already present in the environment that
can be used by organism as such are termed as raw materials such as
oxygen, carbon dioxide, water, some salt etc.

8. Excretion: When chemical reactions use the carbon source and the
oxygen for energy generation, they create by-products that are not only
useless for the cells of the body but could even be harmful. These
waste byproducts are therefore needed to be removed from the body
and discarded outside by a process called excretion. Thus, excretion is
the process of discarding and removal of useless and harmful
byproducts from the body.
Note:
Oxidising reaction: Addition of oxygen or removal of hydrogen takes place.
Reducing reaction: Removal of oxygen or addition of hydrogen takes place.

9. All the biochemical processes taking place in the body of
organisms can be categorised as metabolic processes
(metabolism).
The metabolic processes can be further categorised into two
types:
Anabolic process (anabolism) and catabolic process
(catabolism).
Anabolism creates molecules the body needs for functionality
and it uses energy in the process. e.g. photosynthesis.
Catabolism, on the other hand, breaks down complex
molecules and releases energy which is available for the body to
use. e.g. respiration.

10. QUESTIONS
1.Why is diffusion insufficient to meet the oxygen requirements of
multicellular organisms like humans?
2.What criteria do we use to decide whether something is alive?
3.What are outside raw materials used for by an organisms?
4.What processes would you consider essential for maintaining life?
5.Define the term aerobic and anaerobic respiration.
6.What do you mean by nutrition and excretion?