Q7 of 360 Page 119

What are the functions of plasma membrane? How is the plasma membrane able to perform diverse functions. Give an example of diversity in functioning in any segment of human society.

Plasma membrane has diverse functions which includes providing shape to cell, acting as mechanical barrier between cell contents and environment, selective permeability, flow of information, passage of water, flow of external fluids by cilia or absorption of nutrients by its microvilli etc. Plasma membrane is able to performance varied functions due to adaptation of proteins to form channels, enzymes, carriers, receptors and their attachment to small carbohydrates (oligosaccharides). In human society, every human being has to perform various functions. For example - Mahak is daughter of her parents, student of her school, a table tennis player, sister of her brother, a companion of her pet, a gardner in home garden, a caretaker of her grandparents etc.


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3

One day Muskan saw her mother making pickle. Her mother cut the carrots, turnip and cauliflowers into small pieces, washed them and put them in the sun for few hours. Thereafter, she mixed common salt, oil, paste of onion, ginger and garlic, gur, red chilli, turmeric powder, acetic acid, etc. As per requirement with the cut vegetables and heated them. After cooling, she put the contents in the air tight jar and kept it in the sun for many days.

(i)Why did Muskan’s mother cur the vegetables into small pieces and put them in the sun for few hours?


(ii) Why did she mix common salt in the cut vegetables and heated it? Name the process involved.


(iii) Why did she mix acetic acid?

 4

What is the basis of long life of pickles and jams? What lesson one gets from this fact?

 5

Arvind sometimes go for late ecening walk with his father who has a background of biology. While walking in the colony park, he observed many plants having colour flowers. He also saw gew plants having white flowers. Most of these flowers emit pleasant fragrance (=aroma). Out of curiousity, Arvind asked his father the following questions:

(i) Why do plants have variously coloured flower? Give two reasons.


(ii) Why do certain flowers emit frangrance? How does frangrance of flowers spread in the environment?


(iii) Which scientific phenomenon is obvolved when (a) frangrance spreads in the house at the time of cooking of food in the kitchen; (b) exchange of gases occurs across the respiratory surface.

 7

(i) A fruit is green when unrioe but become beautifully coloured when ripe. How does this change occur?

(ii) What is the importance of this change?


(iii) What is mutualism involved?


(iv) Give an example of such a mutualism in human society.