Class 10 Science Chapter 5: Important & Previous Year Questions – Bihar Board

Correct answer: (C) Enamel

The hard outermost layer of a tooth is enamel; dentine lies under it. The book's «More to know» box on dental caries: bacterial acid softens enamel and dentine (lesson 4).

Correct answer: (C) Stomach

Gastric glands in the wall of the stomach release HCl, pepsin and mucus (lesson 4).

Correct answer: (A) Lipase

Lipase of pancreatic juice breaks emulsified fat into fatty acids and glycerol. Ptyalin = salivary amylase (acts on starch).

Correct answer: (D) all of these

Every living cell of every part of a plant respires; roots, stems and leaves exchange gases by diffusion (lesson 5).

Correct answer: (A) CO₂

At night there is no photosynthesis, only respiration — so CO₂ is released. By day the CO₂ is used up in photosynthesis and O₂ is released (lesson 5).

Correct answer: (A) 02

Fermentation (anaerobic respiration) gives only 2 ATP per glucose; aerobic respiration gives far more (about 36–38 ATP) — lesson 5.

Correct answer: (A) 80 mm Hg

Normal blood pressure is 120/80 mm Hg — 120 systolic, 80 diastolic. It is measured with a sphygmomanometer (lesson 7).

Correct answer: (B) In the leaf

Transpiration is mainly the loss of water vapour through the stomata of the leaf (lesson 8, Activity 5.8).

Correct answer: (D) All of these

Book: wastes are stored in cellular vacuoles, in leaves that fall off, and as resins and gums in old xylem; bark is shed too — so all of these (lesson 8).

Correct answer: (C) Nephron

The nephron is the basic filtration unit of the kidney; the glomerulus and Bowman's capsule are its parts (lesson 8).

Correct answer: (D) All of these

Tannin, resin and gum are all plant wastes; gums and resins collect in old xylem (lesson 8).

Gastric glands of the stomach release three things:

• Hydrochloric acid (HCl): makes the medium acidic so pepsin can act; kills germs that come with food.
• Pepsin: the enzyme that digests proteins.
• Mucus: protects the inner lining from the acid.

👉 A sphincter muscle lets the food into the small intestine a little at a time.

In one complete cycle the blood passes through the heart twice — this is double circulation.

• Pulmonary: right ventricle → lungs (takes O₂) → left atrium.
• Systemic: left ventricle → body organs → right atrium.

Benefit: oxygenated and deoxygenated blood never mix, so the body gets an efficient O₂ supply — needed by birds and mammals (high energy, constant body temperature).

Dialysis works on diffusion across a semi-permeable membrane.

• The patient's blood passes through long tubes with semi-permeable walls, kept in a tank of dialysing fluid.
• The fluid has the same osmotic pressure as blood but no nitrogenous wastes — so urea etc. diffuse out of the blood into the fluid.
• The cleaned blood goes back into the body. (Unlike the kidney, there is no reabsorption.)

A fish uses oxygen dissolved in water — water has far less O₂ than air, so the breathing rate is fast.

Process:

• The fish takes water in through the mouth.
• It forces the water over the gills and out through the gill slits / operculum.
• Gills have many thin-walled blood capillaries; dissolved O₂ diffuses into the blood and CO₂ from the blood into the water.
• Opening of the mouth and of the gill slits go in the same rhythm (Activity 5.6).

Diagram: mouth → gill filaments (capillaries in red) → water out by the operculum (see the lesson 6 figure).

Correct answer: (A) Saprotrophic

Fungi (bread mould, yeast, mushrooms) break food down outside the body and absorb it — saprotrophic nutrition (lesson 3).

Correct answer: (A) buccal cavity

In the mouth, salivary amylase starts breaking starch into sugar (lesson 3, Activity 5.3).

Correct answer: (D) all of these

Nutrition, respiration, transport, excretion — and reproduction too — are processes of living things; the board answer is all of these (lesson 1).

Correct answer: (C) Yeast

Yeast turns pyruvate into ethanol + CO₂ without oxygen — fermentation (lesson 5, Activity 5.5).

Correct answer: (D) O₂

Aerobic = in the presence of oxygen; in mitochondria pyruvate → CO₂ + H₂O + energy (lesson 5).

Correct answer: (C) Glucose

In respiration glucose is oxidised to make ATP — so glucose is called the cellular fuel (lesson 5).

Correct answer: (C) leaves

Mainly through the stomata of the leaves (lesson 8).

Correct answer: (D) circulatory system

The heart pumps blood — the circulatory (transport) system (lesson 7).

Correct answer: (B) Fibrinogen

Fibrinogen (a plasma protein) takes part in clotting. The book says platelets clot the blood at a cut; platelets are not an option, so fibrinogen (lesson 7).

Correct answer: (D) all of these

Vacuoles, leaves that fall, old xylem — all of these (lesson 8).

Correct answer: (C) NH₃

Breaking down proteins/amino acids gives nitrogenous wastes — ammonia (NH₃), then urea or uric acid. Unicellular organisms remove them by diffusion (lesson 8).

Correct answer: (B) excretion

Kidneys filter nitrogenous wastes such as urea out of the blood — excretion (lesson 8).

Villi: countless finger-like projections on the inner wall of the small intestine.

• They greatly increase the surface area for absorption.
• They are richly supplied with blood vessels that take the digested food (glucose, amino acids etc.) to every cell of the body.

Stomata: tiny pores on the surface of leaves (mostly the lower epidermis), each surrounded by two guard cells.

• Job: exchange of gases for photosynthesis and respiration, and transpiration.
• When water flows into the guard cells they swell and the pore opens; when they lose water they shrink and the pore closes — this cuts water loss.

Unicellular organisms have no special excretory organ. Their wastes (such as ammonia, CO₂) pass out by simple diffusion from the cell surface into the surrounding water. Amoeba also throws out undigested food at its surface.

Cleaning the blood with an artificial kidney when the kidneys stop working is dialysis.

• Blood passes through long tubes with semi-permeable walls kept in dialysing fluid.
• Nitrogenous wastes move into the fluid by diffusion; the clean blood returns to the body.
• There is no reabsorption in it.

Nutrition: taking a source of energy (food) from outside into the body and making it usable.

1. Autotrophic nutrition — organisms make their own food from inorganic sources (CO₂, water) using sunlight and chlorophyll — photosynthesis. Green plants, some bacteria.

2. Heterotrophic nutrition — organisms take complex substances from others:

• Saprotrophic: digest food outside the body, then absorb it — fungi (bread mould, yeast, mushrooms).
• Parasitic: feed on a host without killing it — cuscuta (amar-bel), ticks, lice, leeches, tapeworms.
• Holozoic: take in whole food and digest it inside — Amoeba, humans, cows.

👉 Heterotrophs depend fully on autotrophs.