Class 10 Science, Chapter 5 (NCERT). 15 questions by concept. Open “Show answer” for the answer and why.
How to teach this chapter · Common misconceptions & worked visual for this chapter
What is a function of stomata in leaves?
(a) Exchange of gases with the air
Stomata are tiny pores that allow gas exchange between leaves and the air. Carbon dioxide enters through them for photosynthesis. Roots absorb water and minerals from the soil, while phloem transports food.
Which gas is released during photosynthesis?
(d) Oxygen
Photosynthesis uses carbon dioxide and water to make carbohydrates in light. Oxygen is released as a product.
What are the main materials carried by xylem and phloem, in that order?
(c) Water and minerals; food
Xylem mainly carries water and minerals absorbed by roots. Phloem carries food from leaves to other plant parts. The pair is water and minerals; food.
What supplies the energy for loading sugar into the phloem?
(d) ATP from cellular respiration
Loading sugar into the phloem uses energy supplied by ATP from cellular respiration. Sunlight and root pressure do not directly supply energy for this loading.
Which substance in the small intestine digests fats into fatty acids?
(d) Lipase
Pancreatic juice contains lipase, which digests emulsified fats into fatty acids and glycerol. Bile breaks large fat globules into smaller droplets and helps make the intestinal medium alkaline. It contains no digestive enzyme.
What do the villi of the small intestine increase?
(b) Surface area for absorption
Villi are numerous thin-walled fingerlike folds of the small intestine, each with a rich blood supply. They increase the surface area for absorbing digested food. Acid is made by gastric glands in the stomach, and bile comes from the liver.
For each glucose molecule, how much usable energy does anaerobic respiration release compared with aerobic respiration?
(c) Less energy
Anaerobic respiration breaks down glucose only partly, releasing less usable energy per glucose molecule than aerobic respiration. Aerobic respiration uses oxygen to break down glucose completely.
Where in the body does the breakdown of glucose release energy?
(a) In the cells
Glucose is broken down inside cells to release energy during cellular respiration. Breathing moves air into and out of the lungs; it does not itself release energy from glucose.
Compared with inhaled air, how much oxygen does exhaled air contain?
(c) Less oxygen, but still some
The body takes in only part of the oxygen present in inhaled air. So exhaled air has less oxygen and more carbon dioxide than inhaled air, but it still contains oxygen.
What process moves oxygen and carbon dioxide between alveolar air and blood?
(c) Diffusion
Oxygen diffuses from alveolar air into the blood, while carbon dioxide diffuses from the blood into the alveoli. Each gas moves from a region of higher concentration to a region of lower concentration, without active pumping.
What is the main job of platelets in the blood?
(c) Helping the blood to clot
Platelets circulate in the blood and help it clot at points of injury. This helps stop blood from leaking out. Red cells carry oxygen, white cells fight germs, and plasma carries dissolved substances.
What decides whether a blood vessel is called an artery or a vein?
(a) The direction in which it carries blood relative to the heart
Arteries carry blood away from the heart and veins carry it towards the heart, whatever the oxygen content. This is why the pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood.
What does xylem carry, and in which direction does it move through the plant?
(b) Water and minerals, upward
Xylem carries water and dissolved minerals from the roots upward to the stem and leaves. Phloem carries prepared food.
Which substance is present in the initial kidney filtrate but normally absent from urine?
(b) Glucose
Glucose enters the initial kidney filtrate and is normally reabsorbed into the blood. Urea and some water pass out in urine, so filtrate and urine differ in composition.
What function does dialysis perform when the kidneys cannot filter blood adequately?
(d) Removal of urea from the blood
During dialysis, urea diffuses from the blood through a semi-permeable membrane into dialysis fluid. This removes waste but does not permanently repair failed kidneys.
Wrong
The oxygen gas comes from carbon dioxide because CO₂ contains oxygen.
Why it feels right. The oxygen atoms look available in the formula.
Right
The oxygen gas released in photosynthesis comes from water.
Worked example
