Question 1 · MCQ · Analyse · 1 mark
Testing a partly covered leaf
Nutrition in plants
A destarched plant is exposed to sunlight with part of a leaf covered by opaque paper. After the starch test, only the uncovered part turns blue-black. What is supported?
(A) Light is needed for starch formation in the leaf.
(B) Covered tissue contains no living cells.
(C) Sunlight is the source of carbon atoms in starch.
(D) Roots manufacture all the starch.
Show answer and solution
Answer: (A) Light is needed for starch formation in the leaf.
Worked solution: Both parts belong to the same leaf, but only one receives light. With the stated controls, starch in the lit part supports the need for light in photosynthesis. Carbon comes from carbon dioxide, not light.
Question 2 · MCQ · Analyse · 1 mark
A one-way blood-flow problem
Transportation in humans
A heart valve fails to close properly. Which immediate effect is most directly expected?
(A) Blood becomes unable to carry oxygen molecules.
(B) Some blood can flow backward.
(C) All blood cells are destroyed.
(D) The lungs stop exchanging gases instantly.
Show answer and solution
Answer: (B) Some blood can flow backward.
Worked solution: Valves help maintain one-way flow. A valve that does not close can allow regurgitation, reducing efficient forward flow.
Question 3 · MCQ · Analyse · 1 mark
Yeast and a balloon
Respiration
Yeast is mixed with sugar solution in a warm flask under oxygen-limited conditions. A balloon over the mouth slowly inflates. Which gas is mainly responsible?
(A) Nitrogen
(B) Hydrogen
(C) Carbon dioxide
(D) Chlorine
Show answer and solution
Answer: (C) Carbon dioxide
Worked solution: Yeast ferments sugar to ethanol and carbon dioxide. The gas accumulates and inflates the balloon.
Question 4 · MCQ · Analyse · 1 mark
Glucose after filtration
Excretion
Glucose enters the filtrate in a healthy kidney, but normally little or none appears in the urine. What explains this?
(A) All glucose is destroyed in the bladder.
(B) Glucose cannot pass through any filter.
(C) The kidney changes glucose into oxygen.
(D) Glucose is selectively reabsorbed into the blood.
Show answer and solution
Answer: (D) Glucose is selectively reabsorbed into the blood.
Worked solution: Useful substances such as glucose are normally reabsorbed from the nephron filtrate into the blood. Filtration and selective reabsorption are different processes.
Question 5 · A-R · Analyse · 1 mark
Bile and fat digestion
Nutrition and digestion
Assertion (A): Bile helps the digestion of fats even though it contains no digestive enzyme.
Reason (R): Bile emulsifies large fat globules into small droplets, increasing the surface area available to lipase.
(a) Both A and R are true, and R correctly explains A.
(b) Both A and R are true, but R does not correctly explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show answer and solution
Answer: (A) Both A and R are true, and R correctly explains A.
Worked solution: Emulsification increases access for fat-digesting enzymes. Bile also helps provide alkaline conditions in the small intestine.
Question 6 · A-R · Analyse · 1 mark
Identifying the transport tissue
Transport of water
Assertion (A): Phloem is the main tissue carrying water and dissolved minerals upward from roots.
Reason (R): Xylem transports water and minerals from roots towards aerial parts.
(a) Both A and R are true, and R correctly explains A.
(b) Both A and R are true, but R does not correctly explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show answer and solution
Answer: (D) A is false, but R is true.
Worked solution: The assertion names the wrong tissue. Xylem transports water and minerals; phloem mainly translocates food such as sugars.
Question 7 · VSA · Apply · 2 marks
Breathing after a run
Respiration
A student breathes faster after a sprint. Link this response to the energy needs of muscles.
Show answer and solution
Answer: Active muscles need faster energy release, so oxygen supply and carbon dioxide removal must increase.
Worked solution: Higher muscular activity increases the rate of cellular respiration. Faster ventilation helps deliver oxygen and remove the additional carbon dioxide produced.
Question 8 · VSA · Apply · 2 marks
A plant in moving air
Transport of water
Two similar well-watered plants receive the same light and temperature. One is exposed to gentle moving air. Predict which generally loses water faster and explain.
Show answer and solution
Answer: The plant in moving air generally loses water faster.
Worked solution: Moving air carries away water vapour near leaf surfaces, helping maintain a vapour gradient and increasing transpiration when other conditions remain comparable.
Question 9 · SA · Analyse · 3 marks
Matching digestive functions
Nutrition and digestion
A meal contains starch, proteins and fats. Explain one role each of salivary amylase, pepsin and lipase, and identify a suitable site of action for each.
Show answer and solution
Answer: Amylase starts starch digestion in the mouth; pepsin digests proteins in the stomach; lipase digests fats in the small intestine.
Worked solution: Salivary amylase breaks starch into simpler sugars in the mouth. Pepsin acts on proteins in the acidic stomach. Lipase acts on emulsified fat in the small intestine, producing fatty acids and glycerol.
Question 10 · SA · Analyse · 3 marks
Why separate the two circuits
Transportation in humans
Explain why keeping oxygen-rich and oxygen-poor blood largely separate is useful in humans. Name the two circuits through which blood travels.
Show answer and solution
Answer: Separation supports efficient oxygen delivery for a high energy demand; the circuits are pulmonary and systemic circulation.
Worked solution: Pulmonary circulation sends oxygen-poor blood from the heart to the lungs and returns oxygen-rich blood. Systemic circulation distributes that oxygen-rich blood to the body. The four-chambered heart limits mixing and helps maintain efficient oxygen supply.
Question 11 · LA · Analyse · 5 marks
Following water through a nephron
Excretion
Describe how a nephron forms urine: (i) the source of the filtrate; (ii) initial filtration; (iii) selective reabsorption; (iv) adjustment of water reabsorption; and (v) the route by which urine leaves the kidney and is stored.
Show answer and solution
Answer: Blood is filtered in the glomerulus; useful solutes and water are reabsorbed; urine passes to the ureter and bladder.
Worked solution: Blood entering glomerular capillaries is filtered into Bowman’s capsule. Small solutes and water enter the filtrate, while blood cells and most large proteins remain in the blood. Tubules reabsorb useful substances and much water. Water reabsorption varies with the body’s needs and waste load. The remaining urine reaches collecting ducts, the renal pelvis and ureter, and is stored in the urinary bladder.
Question 12 · Case Study · Analyse · 4 marks
Testing the role of carbon dioxide
Nutrition in plants
Two similar destarched potted plants are placed under separate airtight transparent bell jars and kept in the same sunlight. Jar P contains a dish of potassium hydroxide to absorb carbon dioxide; jar Q has a dish of water. After sufficient exposure, their leaves are tested for starch.
Answer the following:
(i) What is the role of potassium hydroxide? [1 mark]
(ii) Which plant is expected to show more starch? [1 mark]
(iii) Explain why the plants are destarched first and why the light conditions must match. [2 marks]
Show answer and solution
Answer: (i) It removes CO₂ from jar P. (ii) Plant Q. (iii) Destarching removes stored starch; equal light isolates CO₂ availability as the tested factor.
Worked solution: Photosynthesis uses carbon dioxide to make carbohydrates. Plant P has less available CO₂, so it produces less starch under the stated conditions. Destarching avoids confusing old stored starch with newly formed starch, and equal light provides a fair comparison.
