12.  Draw a flow chart showing different pathways of breakdown of glucose during respiration.

13.   Name the energy rich molecules synthesised during respiration in living organisms.

ATP or adenosine triphosphate is the energy rich molecule synthesised during respiration.

14.  How is ATP utilized by living beings?

ATP molecule is broken down to produce a fixed amount of energy.  Living organisms use this energy during various life processes.

15.  Describe an activity to demonstrate that air contains carbon dioxide.

Activity to demonstrate that air contains carbon dioxide is as follows:

Procedure

- Take some freshly prepared lime water in a test tube
- Use a syringe or pichkari to pass air in it
- Observe carefully the lime water
Observation - Lime water turns milky
Conclusion Air contains carbon dioxide

16.  Describe an activity to demonstrate that the air we exhale out is rich in carbon dioxide.

Activity to demonstrate that air we exhale out is rich in carbon dioxide is as follows
Procedure:
- Take some freshly prepared lime water in a test tube
- Take a glass tube and blow the air
- Observe the lime water.
Observation:
Lime water turns milky
Conclusion:
Exhaled air contains carbon dioxide.

17.  Describe an activity to demonstrate that fermentation produce carbon dioxide.

Activity to demonstrate that fermentation produces CO₂ is as follows:

Procedure - Take some fruit juice or sugar solution in a test tube
- Add some yeast in this solution
- Fit a one-holed cork with bent glass tube in this test tube.
- Dip the free end of the glass tube into a test tube containing freshly prepared lime water.
- Observe the lime water Observation:
- The mixture of fruit juice and yeast shows formation of froth
- Lime water turns milky Conclusion Fermentation produce CO₂.