Class 10 Science · Chapter 5

Life Processes

431 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 17 of 22

1. Q321 CBSE 2023
   These ​consists of two statements – ​Assertion ​(A) ​and Reason ​(R). Answer this ​question selecting the appropriate option given below :

   Assertion (A): Amoeba takes in food using finger like extensions of the cell surface.

   Reason (R): In all unicellular organisms, the food is taken in by the entire cell surface.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of (A).
   2. (b)Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (c) Assertion (A) is true, but Reason (R) is false.

   Step-by-step solution →
2. Q322 CBSE 2023
   Two statements are given — one labelled as Assertion ​(A) and the ​other ​labelled as ​Reason (R). ​Select ​the correct answer to this question from the codes (a), (b), (c) and (d) ​as given below.

   Assertion (A): The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

   Reason (R): The amount of oxygen dissolved in water is fairly low as compared to the amount of oxygen in air.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

   Step-by-step solution →
3. Q323 CBSE 2023
   These consist of two statements – ​Assertion (A) and Reason ​(R). Answer ​this question selecting ​the ​appropriate ​option given below :

   Assertion (A): Left atrium receives oxygenated blood from pulmonary vein.

   Reason (R): Right atrium transfers deoxygenated blood to the right ventricle, which pumps it to the lungs for oxygenation.

   1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
   2. (b)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
   3. (c)(A) is true, but (R) is false.
   4. (d)(A) is false, but (R) is true.
   Show answer

   (b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).

   Step-by-step solution →
4. Q324 CBSE 2023
   1. (a)Why is it important ​to ​prevent oxygenated and deoxygenated blood from ​mixing in birds and mammals ​?
   2. (b)​Which animals can tolerate some mixing of the ​oxygenated and deoxygenated blood streams ? On what factor does ​the body temperature of these animals ​depend ?
   Show answer

   Mixing would lower the oxygen supply that warm-blooded animals need; amphibians and reptiles tolerate it, and their body temperature depends on their surroundings.

   (a) Birds and mammals are warm-blooded: they keep their body temperature constant and so lose heat to the surroundings all the time. That heat must be replaced continuously by respiration, which calls for a high and steady supply of oxygen. Keeping the two streams apart, with a complete septum in the four-chambered heart, means the blood sent out to the body is fully oxygenated and delivers the maximum oxygen, giving the efficient energy supply such a body needs. (b) Amphibians (such as frogs) and many reptiles (such as lizards), which have a three-chambered heart, can tolerate some mixing. Their body temperature depends on the temperature of their environment, that is, of the surroundings.

   Step-by-step solution →
5. Q325 CBSE 2023
   List ​four ​life-processes that are ​essential ​for maintaining ​life.
   Show answer

   Nutrition, respiration, transportation and excretion.

   The four life processes essential for maintaining life are: (i) Nutrition, (ii) Respiration, (iii) Transportation, and (iv) Excretion.

   Step-by-step solution →
6. Q326 CBSE 2023
   Name the site ​of complete digestion in the ​human body and write the name ​of the end ​products formed of

   1. (i)carbohydrates, ​
   2. (ii)fats, and
   3. (iii)​proteins.
   Show answer

   Complete digestion occurs in the small intestine, giving glucose from carbohydrates, fatty acids and glycerol from fats, and amino acids from proteins.

   Site of complete digestion: the small intestine (bile, pancreatic juice and intestinal juice act on the food there). (i) Carbohydrates $\to$ glucose (simple sugar). (ii) Fats $\to$ fatty acids and glycerol. (iii) Proteins $\to$ amino acids.

   Step-by-step solution →
7. Q327 CBSE 2023
   What ​will ​happen if :

   1. (a)Xylem ​tissue in ​a ​plant is removed ?
   2. (b)​We are injured ​and ​start bleeding ?
   Show answer

   Without xylem, water cannot reach the leaves and the plant wilts and dies; on bleeding, platelets help the blood clot and stop the loss.

   (a) If the xylem is removed, water and dissolved minerals can no longer be conducted from the roots to the stem and leaves. The leaves go on losing water by transpiration, so they wilt; photosynthesis cannot continue for want of water; and the plant, at least all of it above the removed part, dies. (b) When we are injured and start bleeding, the platelets in the blood gather at the injury and help the blood to clot there. The clot plugs the leak, which stops further loss of blood and the fall in pressure that would reduce the efficiency of the pumping system.

   Step-by-step solution →
8. Q328 CBSE 2023
   State the ​role ​of ​the following in ​the process of ​digestion :

   1. (a)Bile juice ​and bile ​salts
   2. (b)Pancreatic ​enzymes
   Show answer

   Bile makes the food alkaline and its salts emulsify fats; pancreatic enzymes (trypsin, lipase, amylase) digest proteins, emulsified fats and starch.

   (a) Bile juice, secreted by the liver and stored in the gall bladder, makes the acidic food coming from the stomach alkaline, so that the pancreatic enzymes can act on it. Its bile salts emulsify fats: they break the large fat globules into smaller globules, which increases the efficiency of enzyme action on the fats. Bile itself contains no digestive enzyme. (b) The pancreas secretes pancreatic juice into the small intestine. Its enzymes include trypsin, which digests proteins (into smaller peptides), and lipase, which breaks down the emulsified fats; it also carries an amylase that continues the digestion of starch.

   Step-by-step solution →
9. Q329 CBSE 2023
   Write one ​specific ​function each ​of the following organs in relation ​with excretion ​in human ​beings ​:

   1. (i)Renal Artery
   2. (ii)​Urethra
   3. (iii)Glomerulus
   4. (iv)Tubular part of nephron
   Show answer

   Renal artery brings blood to the kidney, glomerulus filters it, the tubule reabsorbs useful substances, and the urethra carries urine out.

   (i) Renal artery: it brings blood carrying nitrogenous wastes such as urea from the body into the kidney, at a pressure high enough for filtration. (ii) Urethra: it carries urine from the urinary bladder to the outside of the body. (iii) Glomerulus: a cluster of capillaries in which the blood is filtered under pressure, so that water, glucose, amino acids, salts and urea pass into the Bowman's capsule. (iv) Tubular part of nephron: it selectively reabsorbs glucose, amino acids, most salts and most of the water from the filtrate back into the blood, leaving urine behind.

   Step-by-step solution →
10. Q330 CBSE 2023
    Give ​the name of the enzyme ​present in the ​fluid in our mouth cavity. ​State the gland which produces it. What would happen to ​the ​digestion process if this gland ​stops secreting this enzyme?
    Show answer

    Salivary amylase from the salivary glands; without it starch digestion would not begin in the mouth and would be delayed.

    The enzyme is salivary amylase (ptyalin), present in the saliva. It is secreted by the salivary glands of the mouth. If these glands stopped secreting it, the digestion of starch would not begin in the mouth at all: the starch would pass on unchanged and would be broken down only later in the small intestine, by the amylase of the pancreatic juice. Starch digestion would therefore be delayed and less complete, and chewed food would no longer begin to taste sweet.

    Step-by-step solution →
11. Q331 CBSE 2023
    Name the ​type ​of blood (oxygenated / deoxygenated) transported by each of the following mentioning the ​path ​(i.e. from one ​organ (which ​place) to another (which ​place)).

    1. (i)​Vena cava
    2. (ii)Pulmonary artery
    Show answer

    Both carry deoxygenated blood: vena cava from the body organs to the right atrium, pulmonary artery from the right ventricle to the lungs.

    (i) Vena cava: it carries deoxygenated blood, from the body organs (superior vena cava from the head, neck and arms; inferior vena cava from the trunk and legs) to the right atrium of the heart. (ii) Pulmonary artery: it carries deoxygenated blood, from the right ventricle of the heart to the lungs.

    Step-by-step solution →
12. Q332 CBSE 2023
    List ​the events ​in ​proper sequence ​that take place ​during ​the process of ​photosynthesis.
    Show answer

    Chlorophyll absorbs light, the energy splits water and releases oxygen, then hydrogen reduces carbon dioxide to carbohydrate.

    The events, in order, are: (1) Absorption of light energy by the chlorophyll of the leaf. (2) Conversion of that light energy into chemical energy, and splitting of water molecules into hydrogen and oxygen, the oxygen being released. (3) Reduction of carbon dioxide to carbohydrate by the hydrogen so obtained. Overall: $6{\text{CO}}_2+6{\text{H}}_2\text{O}\underset{\text{chlorophyll}}{\overset{\text{sunlight}}{\to }}{\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2$.

    Step-by-step solution →
13. Q333 CBSE 2023
    How ​is ​oxygen ​transported in ​human beings?
    Show answer

    Oxygen combines with haemoglobin in red blood cells at the lungs and is carried to the tissues, where it is released.

    Oxygen diffuses from the air in the alveoli of the lungs into the blood in the surrounding capillaries. There it combines with the pigment haemoglobin inside the red blood cells to form oxyhaemoglobin, since oxygen is only slightly soluble in plasma. The oxygenated blood is carried by the pulmonary veins to the heart and pumped through the arteries to all the tissues. In the tissues, where the oxygen concentration is low, oxyhaemoglobin breaks up and the oxygen diffuses out into the cells. A small amount of oxygen is also carried dissolved in the plasma.

    Step-by-step solution →
14. Q334 CBSE 2023
    With ​the help of a schematic flow ​chart, show the breakdown ​of glucose in ​a cell ​to provide energy —

    1. (i)in the presence ​of ​oxygen
    2. (ii)in ​lack of oxygen
    Show answer

    Glucose first becomes pyruvate in the cytoplasm; with oxygen this gives carbon dioxide and water, without oxygen ethanol (yeast) or lactic acid (muscle).

    Glucose (6 carbon) breaks down in the cytoplasm into pyruvate (3 carbon) with release of energy. Pyruvate then follows one of three routes: (i) In the presence of oxygen (in the mitochondria): pyruvate $\to$ carbon dioxide + water + energy (a large amount). (ii) In lack of oxygen: in yeast, pyruvate $\to$ ethanol + carbon dioxide + energy; in our muscle cells, pyruvate $\to$ lactic acid + energy.

    Step-by-step solution →
15. Q335 CBSE 2023
    Explain ​in ​brief ​two ways ​by which ​leaves of a plant help in excretion.
    Show answer

    Leaves excrete gaseous wastes and excess water vapour through stomata, and stored wastes like tannins and calcium oxalate crystals when old leaves fall.

    (1) Through the stomata. The many stomata on a leaf let gaseous wastes diffuse straight out: the excess oxygen made in photosynthesis, the carbon dioxide made in respiration, and excess water as vapour by transpiration. (2) By being shed. Wastes such as tannins and crystals of calcium oxalate are stored in the cells of old leaves, and when those leaves fall, the stored waste is carried out of the plant with them.

    Step-by-step solution →
16. Q336 CBSE 2023
    What ​is saliva? ​State ​its ​role in ​the digestion of ​food.
    Show answer

    Saliva is the fluid from the salivary glands; it moistens food for swallowing and its salivary amylase breaks starch into maltose.

    Saliva is the watery, nearly neutral (about pH 6.8) fluid secreted by the salivary glands into the buccal cavity; it contains water, mucus and the enzyme salivary amylase (ptyalin). Its role in digestion is twofold: it moistens and lubricates the food so that it can be chewed and rolled into a bolus that is easily swallowed, and its salivary amylase breaks down the starch in the food into the simple sugar maltose, which is the first chemical digestion the food undergoes.

    Step-by-step solution →
17. Q337 CBSE 2023
    Name ​the part of the human excretory ​system ​where ​nephrons ​are found. Write the structure and ​function ​of nephrons.
    Show answer

    Nephrons are in the kidneys; each has a glomerulus, Bowman's capsule and tubule, and forms urine by filtration and selective reabsorption.

    Nephrons are found in the kidneys (about one million in each kidney). Structure: each nephron begins with a cluster of thin-walled blood capillaries, the glomerulus, enclosed in a cup-shaped bag called Bowman's capsule; from the capsule a long coiled tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule) runs on, surrounded by blood capillaries, and opens into a collecting duct. Function: the glomerulus filters the blood under pressure so that water, glucose, amino acids, salts and urea pass into Bowman's capsule; as this filtrate travels along the tubule, glucose, amino acids, salts and most of the water are selectively reabsorbed into the blood, and the liquid that remains is urine, which is carried away by the collecting duct to the ureter.

    Step-by-step solution →
18. Q338 CBSE 2023
    Two green plants are kept separately ​in oxygen free containers, one ​in the dark and other in sunlight. It was observed that plant ​kept ​in dark ​could ​not survive longer. Give ​reason for ​this observation.
    Show answer

    The dark plant cannot photosynthesise, so no oxygen is produced for its respiration, whereas the plant in sunlight makes its own oxygen.

    Respiration goes on in every cell of a plant all the time, and it needs oxygen. Both containers are free of oxygen, so neither plant can take any from outside. The plant in sunlight carries out photosynthesis, $6{\text{CO}}_2+6{\text{H}}_2\text{O}\to {\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2$, and the oxygen released as a by-product, together with the glucose made, keeps its own respiration going, so it survives. In the dark there is no light to drive photosynthesis, so no oxygen and no food are produced and no oxygen exists in the container. Aerobic respiration therefore stops, the plant cannot release the energy it needs, and it does not survive long.

    Step-by-step solution →
19. Q339 CBSE 2023
    In the process of digestion of food ​in ​human beings, ​two ​protein-digesting enzymes are secreted. ​Name ​the enzymes along with the glands that ​secrete them.
    Show answer

    Pepsin, secreted by the gastric glands of the stomach, and trypsin, secreted by the pancreas.

    (1) Pepsin, secreted by the gastric glands in the wall of the stomach as part of the gastric juice; it works in the acidic medium made by the hydrochloric acid and breaks protein into peptides. (2) Trypsin, secreted by the pancreas in the pancreatic juice; it works in the alkaline medium of the small intestine and continues the digestion of proteins into smaller peptides, which the enzymes of the intestinal juice finally convert to amino acids.

    Step-by-step solution →
20. Q340 CBSE 2023
    Name the ​process by which the ​amount of urine produced in human ​beings ​is regulated. ​Where and how is ​this process ​carried ​out?
    Show answer

    Selective reabsorption in the tubular part of the nephron regulates urine volume according to the body's excess water and dissolved waste.

    The process is selective reabsorption. It is carried out in the tubular part of the nephron, the functional unit of the kidney, where the tubule is surrounded by a network of blood capillaries. As the glomerular filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and most of the water are reabsorbed into the blood. The amount of water reabsorbed depends on how much excess water there is in the body and on how much dissolved nitrogenous waste has to be excreted, so the volume of urine finally produced is regulated there.

    Step-by-step solution →