Class 10 Science Chapter 5: Life Processes worksheet with answer key

Answer: (c) starch

Unused carbohydrate is stored as starch, the plant's energy reserve. Glycogen is the reserve in which animals store energy.

Answer: (b) starch into simple sugar

Saliva contains salivary amylase, which breaks starch, a complex molecule, into simple sugar.

Answer: (c) Fats

Bile salts break large fat globules into smaller ones so that lipase can act efficiently. Without bile the fat stays in large globules and is poorly digested.

Answer: (d) increase the surface area for absorption

Villi are finger-like projections that increase the surface area for absorption and are richly supplied with blood vessels.

Answer: (b) Three

Glucose is a six-carbon molecule and pyruvate, formed from it in the cytoplasm, is a three-carbon molecule.

Saprophytes break food down outside the body and then absorb it, e.g. bread mould, yeast, mushroom. Parasites derive nutrition from a living plant or animal without killing it, e.g. cuscuta, tick, louse, leech, tape-worm.

• saprophytic: breaks food down outside the body and absorbs it, with one example (bread mould, yeast or mushroom) (1)
• parasitic: feeds on a living host without killing it, with one example (cuscuta, tick, louse, leech or tape-worm) (1)

Water flows into the guard cells, they swell and the pore opens (it closes when they shrink). Large amounts of water can be lost through open stomata, so the plant closes them when carbon dioxide is not needed for photosynthesis.

• guard cells take in water and swell, opening the pore (1)
• closing prevents the loss of large amounts of water (1)

Temporary finger-like extensions of the cell surface fuse over the food particle to form a food-vacuole, where it is broken down and the simple substances diffuse into the cytoplasm. Undigested material is moved to the cell surface and thrown out.

• finger-like extensions surround the particle and form a food-vacuole (1)
• undigested matter is moved to the surface and thrown out (1)

(a) Plants do not move and much of the plant body is dead tissue, so their energy needs are low. (b) Root pressure by itself is unlikely to be enough to move water over the heights seen in plants. (c) By day, with the stomata open, evaporation of water from leaf cells creates a suction, the transpiration pull, which pulls water up the xylem from the roots.

• (a) no movement and much dead tissue, so low energy needs (1)
• (b) root pressure is too small for such heights (1)
• (c) transpiration pull: evaporation from leaves creates suction through the xylem (1)

(a) Crushing gives small particles of uniform texture, and saliva wets the food so its passage along the soft lining of the canal is smooth. (b) These peristaltic movements push the food forward from the mouth to the stomach. (c) The sphincter releases food into the small intestine in small amounts.

• (a) small uniform particles; smooth passage along the soft lining (1)
• (b) peristalsis pushes food along to the stomach (1)
• (c) food released into the small intestine in small amounts (1)

De-oxygenated blood from the body enters the right atrium through the vena cavae as the atrium relaxes. The atrium contracts and the right ventricle dilates to receive the blood. The right ventricle contracts and pumps it through the pulmonary artery to the lungs. Valves stop the blood from flowing backwards when the atrium or ventricle contracts.

• vena cavae to right atrium, then to right ventricle (1)
• right ventricle pumps through the pulmonary artery to the lungs (1)
• valves prevent backflow when the chambers contract (1)