Sunday 4 June 2017

CBSE Class 10 - Biology - Life Processes (Holiday Assignment) Q & A (#cbsenotes)

Life Processes 

(Assignment Q & A) 

CBSE Class 10 - Biology - Life Processes (Holiday Assignment) Q & A (#cbsenotes)
Structure Of Leaf
credits: Zephrys, undr CCAS 3.0, Wikimedia Commons

Q1. Where are chloroplasts present in the leaf?

Answer: Below the epidermis, there are layers of palisade cells that contain chloroplasts.

Q2.  Name the pigments that can absorb solar energy. Also name the enzyme required for photosynthesis.

Answer: Chlorophyll. RuBisCo (Ribulose-1,5-bisphosphate carboxylase/oxygenase), a protein enzyme is required to initiate photosynthesis.

(Note: RuBisCo is the most abundant protein in the world due to its presence in green plants.)

Q3. Name one organism each having saprophytic and parasitic and holozoic nutrition.

Saprophytic: Mushroom, yeast
Parasitic: Cuscutta (Dodder plant), Ring Worm, Leech
Holozoic: Human, amoeba

Q4. Enlist two functions of bile juice of liver.

1. Bile neutralized the acidic medium of food coming from stomach and  makes it alkaline.
2. It breaks the large fat globules into smaller ones, this increases the enzyme action.

Q5. Write four factors which affects the process of photosynthesis

1. Light intensity, its quality and variation. (e.g. In red light, the rate of photosynthesis is higher. )
2. Temperature
3. CO₂ concentration.
4. Availability of Water
5. Other factors like histology of leaf and amount of chlorophyll present.

Q6. Why/What are molecular movements needed for life?

Answer: Molecular movements refer to molecules of various compounds that participate in different bio-chemical activities occurring at cellular level. e.g. For photosynthesis, molecules of CO₂ and Water are taken in by plants from external environment. Similarly, for respiration oxygen molecules are transported by blood to each cell of the body. These bio-chemical activities are required to grow, reproduce, repair and maintain the cells of the body. There for molecular movements are important for life survival.

Q7. What are enzymes?

Answer: Enzymes are bio-catalysts whose presence speed up/down the rate of biochemical reactions. e.g. digestion (break down) of proteins, carbohydrates and fats occur in the presence of digestive enzymes (e.g. amylase, trypsin, lipase etc.). Deficiency of enzyme in a body may cause a disease also. e.g. Albinism is due to absence or defect of tyrosinase, a copper-containing enzyme.

Q8. Name the enzymes present in saliva, gastric juice and pancreatic juice. Write their functions.

Saliva: Salivary amylase (digests starch into maltose)
Gastric Juice:
HCl - Makes the medium acidic for the action of pepsin.
Pepsin - Acts on proteins and converts into peptones and proteoses.

Pancreatic Juice:
Amylase - Acts on starch and glycogen and converts into maltose.
Trypsin - Acts on proteins and converts into peptides and peptones.
Lipase  - Acts on emulsified fats and converts into fatty acids and glycerol.  

Q9. Which muscle releases the food from stomach to small intestine? 

Answer: Sphincter muscles.

Q10. Why herbivores have longer small intestine and carnivores have short small intestine?

Answer: The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

Q11. Write the final products of carbohydrates, proteins and fats.

carbohydrates - glucose
proteins  - amino acids
fats  - fatty acids and glycerols.

Q12. What is the role of acid in our stomach?

The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. (called proteolysis)

Kills the microorganisms that exist in the food we eat.

Q13. How is small intestine designed to absorb digested food?

Answer: The digested food is taken up by the walls of the intestine. The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

Q14. How can you show that chlorophyll is necessary for photosynthesis?


1. Take a potted plant like croton whose leaves are partly green and partly white. The green part of the leaf has chlorophyll but the white part of the leaf does not have chlorophyll.

2. Place this plant in a completely dark place for about three-four days to destarch its leaves.

3. Take out the potted plant from the dark place and keep it in bright sunshine for three to four days.

4. Pluck the variegated leaf from the plant, boil it in water for a few minutes and then remove its green colour 'chlorophyll' by boiling it in alcohol. The green parts of the leaf get decolourised. We get a decolourised leaf.

5. Wash the decolourised leaf with hot water to soften it and remove any chlorophyll which may be sticking to it.

6. Pour iodine solution over the colourless leaf and observe the change in colour of the leaf.

7. We find that the outer part of leaf which was originally white (without chlorophyll) does not turn blue-black on adding iodine solution showing that no starch is present in this outer part of the leaf.
From this observation we conclude that the photosynthesis to make starch does not take place without chlorophyll.

8. The inner part of leaf which was originally green (contained chlorophyll) turns blue-black on adding iodine solution showing that starch is present in this inner part of the leaf. From this observation we conclude that the photosynthesis to make starch takes place in the presence of chlorophyll.
Thus, chlorophyll is necessary for the process of photosynthesis to take place.

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