CBSE Guess > Papers > Question Papers > Class X > 2008 >Science > Science Theory

Q. 19. Name the two ways in which glucose is oxidised to provide energy in various organisms.

Ans. The two ways in which glucose is oxidised to provide energy are :
(i) Aerobic Respiration : oxidation of glucose in the presence of oxygen.
(ii) Anaerobic Respiration : oxidation of glucose in the absence of oxygen

Q. 20. How is ozone formed in the upper atmosphere? Which compounds are responsible for the depletion of ozone layer?

Ans. (a) Ozone is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas. The high energy ultraviolet radiation coming from the sun splits oxygen gas into free oxygen atoms.

The free oxygen thus produced reacts with an oxygen molecule to form an ozone molecule.

O₂ + O = O₃

Ozone

(b) The depletion of Ozone layer is due to the use of chemicals called chloro fluoro carbons (CFC).

Q. 21. Study the following diagram :

Name the parts labelled ‘A’ and ‘B’ and state one function of each.

Ans. A → Stomatal pore Function :
• Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis.
B → Guard Cell
• The opening and closing of the stomatal pore is a function of the guard cells.

Science 2008 Question Papers Class X
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