S2 Science: Respiration, Circulation And Excretion (Paper 1 (basics))

S2 Science: Respiration, Circulation and Excretion (Paper 1 (basics))

2026-11-14

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Tutor Prep Guide · Respiration and gas exchange, features of alveoli, blood components and the three vessel types, the four heart chambers and double circulation, kidney filtration and reabsorption, dialysis and sweat

S2 Science: Respiration, Circulation and Excretion (Paper 1 (basics))

This paper starts from the basic definitions and covers the purpose and equation of respiration, the order of the airway, what happens in the chest when breathing in, the three features of alveoli, the four blood components and the three vessel types, the structure of red blood cells, and finishes with the three routes of excretion and a common error about the direction of circulation.

Direct answers　Respiration releases energy and its equation must include glucose, oxygen, carbon dioxide, water and energy; breathing in needs the diaphragm to flatten and ribs to rise; alveoli are many, thin walled and well supplied with capillaries; only veins have valves; the three routes of excretion are kidneys, lungs and skin; blood leaves the heart through arteries.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S2 Science: Respiration, Circulation and Excretion
Level	S2

02　Questions (10 items)

FoundationWhat is the main purpose of respiration?
FoundationWrite the word equation for aerobic respiration.
FoundationIn which order does air pass from the nose to the blood?
IntermediateWhat happens to the diaphragm and ribs when you breathe in?
IntermediateWhich three features of alveoli help gas exchange?
IntermediateWhat are the four components of blood?
ChallengeWhich features make a red blood cell good at carrying oxygen?
ChallengeHow do the walls of arteries, veins and capillaries differ?
ChallengeWhat are the three main routes by which the body excretes waste?
Error redoA student writes the circulation as heart -> vein -> capillary -> artery -> heart. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	To release the energy stored in food so that cells can use it	Respiration breaks down glucose and releases the chemical energy stored in it into a form cells can use.
2	Glucose + oxygen -> carbon dioxide + water + energy	The reactants are glucose and oxygen, and the products are carbon dioxide, water and energy, most of which is lost as heat.
3	Nasal cavity -> trachea -> bronchus -> bronchiole -> alveolus	The airway is only a passage; gas exchange actually happens in the alveoli at the end of it.
4	The diaphragm contracts and flattens downwards, the ribs move up and out, so the chest volume increases	The larger chest volume lowers the pressure inside the lungs below atmospheric pressure, so air is drawn in.
5	A very large number giving a huge surface area, a wall only one cell thick, and a dense network of capillaries outside	A large area and a short diffusion distance both speed up diffusion, and the capillaries carry oxygen away at once.
6	Red blood cells, white blood cells, platelets and plasma	Plasma carries dissolved substances, red cells carry oxygen, white cells defend the body and platelets clot the blood.
7	It contains haemoglobin, has no nucleus when mature, and is biconcave so its surface area is larger	Haemoglobin binds oxygen where oxygen is plentiful and releases it where it is scarce, so oxygen travels from lungs to tissues.
8	Arteries have thick elastic walls, veins have thin walls with valves, and capillary walls are one cell thick	Arteries take the high pressure from the heart, while veins are at low pressure and rely on valves to stop backflow.
9	The kidneys (urea in urine), the lungs (carbon dioxide and water vapour) and the skin (sweat)	Excretion means removing waste made by metabolism, which is different from passing out undigested food.
10	The directions are reversed: it should be heart -> artery -> capillary -> vein -> heart	An artery carries blood away from the heart and a vein brings it back, so the route must start at the heart.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For respiration and circulation questions ask three things: whether the question is about structure, process or numbers, which way the air or blood is moving, and whether the units have been converted correctly.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.