PYQs (Ch 5: Life Processes)

These are some PYQs (previous year questions) from the CBSE board for Class 10 Science; Chapter 5: Life Processes.

By practicing these questions, you will get an idea of what type of questions may appear in the examination.

Question 1:
In human alimentary canal, the specific enzym/juice secreted in locations (i), (ii) and (iii) are

(a) (i) Amylase (ii) Pepsin (iii) Bile
(b) (i) Amylase (ii) Bile (iii) Trypsin
(c) (i) Lipase (ii) Amylase (iii) Pepsin
(d) (i) Trypsin (ii) Bile (iii) Amylase

1 mark; CBSE 2022

Answer:
(b)
Saliva is secreted in the mouth. Saliva contains an enzyme called salivary amylase for digestion of carbohydrates.
Liver secretes bile to emulsify fat.
Pancreas secretes pancreatic juice which contains enzyme trypsin for digestion of proteins.

Question 2:
Opening and closing of stomata is due to
(a) high pressure of gases inside the cells
(b) movement of water in and out of the guard cells
(c) stimulus of light in the guard cells
(d) diffusion of CO2, in and out of the guard cells.

1 mark, CBSE 2023

Answer:
(b)

Question 3:
Assertion (A): The inner walls of the small intestine have finger like projections called villi which are rich in blood.
Reason (R): These villi have a large surface area to help the small intestine in completing the digestion of food.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true and (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

1 mark, CBSE 2023

Answer:
(a)
Villi, finger-like projections in the intestine, increase the surface area for absorption. Blood vessels in the villi carry absorbed nutrients to cells throughout the body.

Question 4:
Water in the root enters due to
(a) the function of the root to absorb water
(b) difference in the concentration of ions between the root and the soil
(c) excess water present in the soil
(d) diffusion of water in the roots

1 mark, CBSE 2023

Answer:
(b)
Water needed by plants is absorbed by roots. The root hair absorb water from soil by osmosis. Difference in concentration of ions is created between roots and soil which enables water to enter into roots to compensate difference in concentration.

Question 5:
Assertion (A): The walls of atria are thicker than those of the ventricles.
Reason (R): Ventricles have to pump blood into various organs at high pressure.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the assertion (A)
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A)
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

1 mark, CBSE 2023

Answer:
(d)
The walls of ventricles are thicker than walls of atria.

Question 6:
The length of small intestine in a deer is more as compared to the length of small intestine of a tiger. The reason for this is
(a) mode of intake of food
(b) type of food consumed
(c) presence or absence of villi in intestines
(d) presence or absence of digestive enzymes

1 mark, CBSE 2022

Answer:
(b)
Herbivores such as deer 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.

Question 7:
In spring, sugar stored in root or stem tissue of plants is transported to the buds for
(a) the energy needs of the buds to grow
(b) temperature regulation
(c) balancing the storage in different organs
(d) diffusion process

1 mark, CBSE 2022

Answer:
(a)
In spring, new buds are formed. These buds need more energy to grow than other parts of the plant. This energy comes from the sugar stored in root or stem tissue and is transported to the buds by phloem.

Question 8:
The separation of the right side and the left side of heart is useful to
(a) keep oxygenated blood from mixing with deoxygenated blood
(b) allow a slow supply of oxygen in the body
(c) supply energy to animals with low energy needs
(d) often change their body temperature.

1 mark, CBSE 2022

Answer:
(a)
The right and left sides of the heart are separated by a muscular wall that prevents mixing of oxygenated with deoxygenated blood. Such separation allows a highly efficient supply of oxygen to the body.

Question 9:
Which part of the nephron in human kidney, serves the function of reabsorption of certain substances
(a) Glomerulus
(b) Bowman’s Capsule
(c) Tubules
(d) Collecting Duct

1 mark, CBSE 2022

Answer:
(c)
The function of tubules of nephron is to allow the selective reabsorption of useful substances like glucose, amino acids, salts and water into the blood capillaries.

Question 10:
The energy released during cellular respiration is used to synthesise
(a) ribosomes
(b) RBC
(c) ATP
(d) mitochondria

1 mark, CBSE 2022

Answer:
(c)
The energy released during cellular respiration is immediately used to synthesise a molecule called ATP which is energy currency of the cell and is used as fuel for cellular activities.

Question 11:
Two green plants are kept separately in oxygen-free containers, one in the dark and the other in sunlight. It was observed that plants kept in the dark could not survive longer. Give a reason for this observation.

2 marks, CBSE 2023

Answer:
The plant kept in the dark could not survive longer because it will not be able to produce the oxygen required for its respiration by the process of photosynthesis.
Oxygen is evolved as the byproduct of photosynthesis during the photolysis of water and helps plants to survive longer.

Question 12:
Differentiate between Artery and Vein.

2 marks, CBSE 2015

Answer:

ArteryVein
Arteries carry blood away from the heart.Veins transport blood toward the heart.
They have thick and flexible walls to endure higher pressure of blood. They have thinner wall but there are valves in them at regular distance to prevent back flow of blood especially when blood is returning back to heart from lower organs.

Question 13:
What are enzyme? Do they play some role in our digestive system too?

2 marks, CBSE 2013

Answer:
They are biocatalyst, which increase or decrease the rate of a biochemical reaction. The enzyme present in our digestive system help to breakdown of complex molecules of food into simpler ones.

Question 14:
(a) How is oxygen and carbon dioxide exchanged between blood and tissue? How are the gases transported in human being?
(b) What is haemoglobin?

3 marks, CBSE 2017

Answer:
(a) Exchange of gases in tissues occurs through diffusion. Oxygen is carried as oxyhaemoglobin from lungs to tissues. It dissociates and carbon dioxide diffuses out into blood from tissues. It is transported in dissolved form and reaches lungs where again it diffuses to alveoli.
(b) Haemoglobin is a respiratory pigment. It is a red coloured protein present in red blood cells. Haemoglobin has affinity for O2.

Question 15:
How is oxygen and carbon dioxide transported in human being?

5 marks, CBSE 2016

Answer:
Exchange of gases in tissues:
– 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.
– 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.
– The CO2 mostly dissolved in blood plasma reaches the lungs, from where it is expelled out during exhalation.

Mechanism of Inhalation: The lung cavity expands when diaphragm and rib muscles contract. This increasing the volume inside lung 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 lung cavity comes back to its original size as diaphragm muscles relax. Air containing CO2 is exhaled out through bronchi, trachea and nostrils.

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