F3 BIO OPENER TERM 3 2026 MS (1)

231BIOLOGYFORM 3 TERM 3 OPENER EXAM 2026MARKING SCHEME

SECTION A (40 MARKS)

1. (a) (i) Condenser; (1 mk) (ii) Fine adjustment knob; (1 mk)

(b) Total magnification = Eyepiece magnification x Objective magnification; = 10 x 40; (1 mk) = X400; (1 mk) (Note: must have X or times)

2. (a) Any two: (2 mks) - They are protein in nature; - They are specific in action; - They are biological catalysts / alter the rate of chemical reactions; - They are affected by temperature; - They are affected by pH; - They remain unchanged at the end of a reaction;

(b) Increase in temperature increases the kinetic energy of enzyme and substrate molecules; leading to more frequent successful collisions between enzyme active sites and substrates; (2 mks)

3. (a) Plasmolysis; (1 mk)

(b) Hypertonic solution; A solution whose concentration is higher than that of the cell sap; causing the cell to lose water by osmosis; (max 2 mks)

(c) Osmosis; (1 mk)

4. (a) Pulmonary vein; (1 mk)(b) Renal vein; (1 mk)(c) Hepatic portal vein; (1 mk)

5. (a) RQ = Volume of CO2 produced / Volume of O2 consumed; = 18 / 26; (1 mk) = 0.69; (1 mk)

(b) Lipids / Fats / Oils; (1 mk) (Because RQ is approx 0.7)

6. (a) Glomerulus / Bowman's capsule; (1 mk)

(b) Any two: (2 mks) - Highly coiled to slow down the filtrate / provide large surface area for reabsorption; - Has microvilli to increase surface area for selective reabsorption; - Highly vascularised / surrounded by blood capillaries to transport reabsorbed substances; - Cells have numerous mitochondria to provide energy (ATP) for active transport; - Thin epithelium for a short diffusion distance;

(c) Urea / Water / Salts / Lactic acid; (1 mk)

7. (a) Any two: (2 mks) - Body divided into three regions (head, thorax, abdomen); - Three pairs of walking legs; - Most have wings; - One pair of antennae; - Have spiracles for gaseous exchange;