CBSE Class 10 - Science - CH6 Life Processes
(Photosynthesis)
Photosynthesis
Photosynthesis Process
Q&A
Q1: What is photosynthesis?
Answer: The process by which green plants make their own food from carbon-dioxide and water in the
presence of sunlight and chlorophyll is called photosynthesis.
During this process oxygen gas is released. This process can be represented as:
6CO2 + 12H2O
➞CH
6
12O6
+ 6H2O + 6O2
The green plants convert energy of sunlight into chemical energy by making glucose.
The extra glucose formed changes into starch which is stored in leaves.
The Oxygen released comes from the water.
Q2: Define Translocation.
Answer: Transportation of food from photosynthetic parts of the plant to the non-green part of the plant
through phloem is known as translocation.
Q3: What are the important events occur during photosynthesis process?
Answer: The following events occur during this process:
1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and
oxygen. (Light Reaction)
3. Reduction of carbon dioxide to carbohydrates. (Dark Reaction by Calvin Cycle)
Q4:Mention the conditions for photosynthesis. Also mention the process involved in each of
these steps.
Answer:
i) SUNLIGHT
Chlorophyll of the leaves of the plant trap sunlight and converts them into chemical energy during
photosynthesis. Plant utilizes visible light only which is made up of 7 colours and green colour is least
absorbed ( it reflects green the most - that's why the leaves appear green).
ii) CHLOROPHYLL
Chlorophyll is a green pigment mainly present in the leaves of the plant. There are many types of
chlorophyll named a, b, c, d, e and bacterio-chlorophyll. Chlorophyll a and chlorophyll b are most
abundently present in the nature.
iii)CARBON DIOXIDE
Plants take carbon dioxide through stomata to make glucose(food for the plants).
iv) WATER
Water is absorbed by the roots of the plants through osmosis. Through xylem, water is tranported to all
parts of the plant.
Q5: Name other two pigments which absorb sunlight ( other than chlorophyll ).
Answer: Carotenoids and Fucoxanthin
Q6: How do aquatic plants get oxygen for photosynthesis?
Answer: Aquatic plants obtain carbon dioxide through the process of diffusion.
Q7: Where does light reaction occur?
Answer: In the grana thylakoids of chloroplasts.
Q8: Where does dark reaction occur?
Answer: In the stroma of chloroplasts.
Q9: Which wavelength of light is best absorbed by chlorophyll?
Answer: Red colour wavelength
Q10: Why do most plants appear green in colour?
Answer: The green pigment of chlorophyll absorbs all light colours and reflect the green light.
Q11: Which products formed during light reaction in photosynthesis process are used by dark
reaction?
Answer: NADPH and ATP
Q12: What is the function of thylakoid membranes in chloroplast?
Answer: Thylakoid membranes provide large surface area for light absorption.
Q13: Write down the full form of the following:



ADP
ATP
NADP
Answer:
ADP: Adenosine diphosphate
ATP: Adenosine triphosphate
NADP: Nicotinamide adenine dinucleotide phosphate