Long Answer -Class 10 -Science- Biology-Chapter 5 – Life Processes

Class 10 -Science-Long Answer – Biology-Chapter 5 – Life Processes

Q1. How is oxygen and carbon dioxide transported in human being? Explain clearly how the air is inhaled and exhaled during breathing in humans.

Ans :   Exchange of gases in tissues:

a. Most of oxygen is carried by haemoglobin in blood. On reaching the tissues, it gets diffused into the cells as it is in higher concentration than in the cells.

b. The carbon dioxide, which is formed in the cells, gets accumulated there in higher concentration as compared in the blood, now diffused into the blood.

c. The CO2 mostly dissolved in blood plasma reaches the lungs, from where it is expelled out during exhalation.

Mechanism of Inhalation: The thoracic cavity expands when diaphragm and rib muscles contract. The thorax moves upwards and outwards, increasing the volume inside thoracic cavity. The air pressure in the cavity decreases, hence the air rushes into the lungs through nostrils, trachea and bronchi.

Mechanism of Exhalation : Exchange of gases between alveolar sacs and blood occurs and air having CO2 enters the alveoli. The thoracic cavity comes back to its original size as diaphragm muscles relax. Air containing CO2 is exhaled out through bronchi, trachea and nostrils.

Q2. How are water and minerals absorbed and transported in the plants?

Ans : 1. Transpiration is the process of removal of water vapors from the aerial parts of a plant, mainly through stomata in the leaves.

2. There are two conducting tissues of plants: first is xylem and second is phloem. Tracheids and vessels which are two kinds of elements of xylem.

3. Tracheids are found in all vascular plants. They are spindle shaped, have only pits and are not very efficient.

4. Vessels are found in flowering plants, are tube like, have perforation plates and pits making them more efficient.

5.When loss of water in vapour occur from leaves of plants due to transpiration, deficit of water is created in the leaves. Evaporation of water molecules from the cells of a leaf creates a suction force which pulls water from the xylem cells.

 6. Water and minerals dissolved in it move up to leaves from root through tracheids and vessels, pulling water and minerals upward through xylem elements-ascent of sap. Thus transpiration helps in upward movement of water from roots to leaves.

7. The roots of a plant absorb water and dissolved substances from the soil, which is needed by the aerial parts of the plants. As such these substances are to be transported from roots up to stem, leaves and flowers.

Q3. What are the different components of blood? Give the function of each of them. 

Ans : Blood is a liquid connective tissue. It is chiefly formed of two components:

a. Fluid matrix or plasma: It is of pale colour and transports much substance like dissolved carbon dioxide, glucose, amino acids, urea etc. has mainly water, some proteins like albumin, fibrinogen (blood clotting protein) and many other substances to be transported.

b. Cellular elements which are of three types:

(1) Red blood corpuscles (R.B.C) or erythrocyt. es, which transport O2 and CO2 . They are enucleated, disc shaped, full of a red colored protein pigment, hemoglobin.

(2) White blood corpuscles (W.B.C) or leucocytes, which fight disease-causing agent. They are larger, nucleated and are of different types.

(3) Blood platelets or thrombocytes, which help in blood clotting. They are fragments of some larger cell hence do not have nucleus..

Q4. Usman collected her saliva and mixed it with liquid A in the test tube. In another test tube she took only liquid A after about 10 minutes, she added a few drops of iodine solution to the mixture in the first test tube. It did not show any colour but when she treated the other test tube with iodine, a blue black colour appeared. Now answer the following questions:

a. What is the aim of this activity?

b. What is liquid A?

c. Why did the first test tube not show any colour change with iodine while the second one did?

d. Which enzyme is responsible for such a result?

e. Why does a piece of bread chewed for a long time tastes sweet?

Ans : a. To show the action of salivary amylase on starch.

b. Liquid A is starch.

c. The first test tube did not show any colour change with iodine because starch was not present anymore in it. It was already digested by salivary amylase present in saliva. The colour of liquid in the second one changed to blue black as the starch was still unchanged due to absence of the enzyme.

d. Salivary amylase enzyme is responsible for such a result.

e. A piece of bread chewed for a long time tastes sweet because the starch is broken down by salivary amylase to maltose sugar.

Q5. (i)Explain the importance of the following:

(a)  salivary amylase

(b)  villi

(c)  pepsin

 (ii) Explain how oxygenated blood from this chamber is sent to all parts of the body.

 Ans :

 (i) (a) Salivary amylase: It’s an enzyme present in the saliva, secreted by salivary glands. It digests starch into maltose there by starting the digestion of carbohydrate in the buccal cavity.

(b) Villi: They increase the surface area for absorption of digested food into the blood.

(c) Pepsin: It is a digestive enzyme secreted by gastric glands. It is responsible for the digestion of proteins in stomach.

(ii) When the left atrium contracts, the oxygenated blood is poured into the left ventricle. When the left ventricle contracts the blood is pumped into the aorta, the largest artery which distributes it to all the parts of the body through arteries.