1.  What is respiration?

The process of breakdown of food in the cells to generate energy for various life processes is called respiration.

2.  Why do organisms require the process of respiration?

All living organism require energy to survive, maintain and sustain their life processes.
Respiration is oxidation of food to produce energy in the form of ATP. This energy rich chemical compound serves as an energy currency in all life processes.

3.  Name the chemical compound that acts as the starting material for the breakdown process during respiration.

Glucose

4.  Do all organisms follow same pathway to generate energy through respiration?

No, organisms follow different pathways to generate energy.

5.  Name two main types of pathways followed by living organisms during respiration.

Two main types of pathways followed during respiration are
(i) Aerobic respiration
(ii) Anaerobic respiration

6.  Explain the first step that is common in all cases of respiration. Where does it take place?

In all organisms the first step during the process of respiration is the breakdown of glucose molecules (six carbon) into pyruvate (three carbon)
This step (Glycolysis) takes place in the cytoplasm of the cell.

7.  What is fermentation?  Why is it also referred as anaerobic respiration?

In yeast and many bacteria, the pyruvate molecule formed in the first step of respiration is further converted to ethanol, (2 carbon) and carbon dioxide in absence of oxygen.  Energy is also produced during the reaction.
Since the process takes place in absence of air or oxygen, it is also called as anaerobic respiration.

8.  Explain the process of aerobic respiration.

- Aerobic respiration takes place in most of the cells of multicellular organisms.
- It occurs in the mitochondria of the cell.
- This process requires presence of oxygen.
- It involves the breakdown of pyruvate molecule (three carbon) to three molecules of carbon dioxide (one carbon).
- Water is also produced in the process
- This process releases more energy as it involves complete breakdown of glucose.

9.  Name a part of our body where anaerobic respiration may occur due to lack of oxygen.

Muscle cells

10.  Explain the process of anaerobic respiration taking place in muscle cells.

During anaerobic respiration due to lack of oxygen in muscle cells, pyruvate is converted into lactic acid (3-carbon molecule). Energy released in the process is used by muscle cells.

11.  Differentiate between aerobic and anaerobic respiration taking place in muscle cells.

Differences between aerobic and anaerobic respiration is as follows:

Parameter	Aerobic Respiration	Anaerobic Respiration
Oxygen presence	Takes place in the presence of oxygen	Takes place in absence of oxygen
End products	CO2 + water + energy	Lactic acid / Ethanol + CO2 + Energy
Breakdown of glucose	Complete breakdown of glucose	Incomplete breakdown of glucose
Energy released	More (36 / 38 ATP)	Less (2 ATP)
locatio	Cytoplasm and Mitochondria	Cytoplasm