Chapter 6 Practice Paper: Human Digestive System — mark scheme (print)

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QQ/S2SCI/CH6

Secondary 2 · Lower Secondary Science (G2 / G3)

Mark scheme

Human Digestive System

Chapter 6 Practice Paper · Maximum mark: 30

Notes for markers

Award one mark for each point marked [1], up to the marks shown for the part.
Accept answers worded differently that show the same understanding.
Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

Question	Answer
1	ALarge molecules are broken down so the smaller products can enter the blood.	1
2	CThe order starts mouth, gullet, stomach, then small intestine.	1
3	BThe small intestine is the main site of absorption. The large intestine absorbs water.	1
4	DProteases digest proteins. Lipases digest fats. Carbohydrases digest carbohydrates.	1
5	ALipases act on fats.	1
6	CThe large intestine absorbs water from what the small intestine did not absorb. Most glucose is absorbed earlier, in the small intestine.	1
7	DEgestion removes food that was never absorbed. Excretion removes waste the body has made, such as carbon dioxide.	1
8	BA larger surface area gives the enzymes more food to act on.	1
9	AStarch is a carbohydrate, so carbohydrases digest it.	1
10	CFood meets the mouth first, then the gullet, the stomach and the small intestine.	1

Section B: Structured questions[20 marks]

Question	Answer and marking points	Marks
1(a)	Carbohydrases [1]	1
1(b)	In the mouth. [1]	1
1(c)	In the small intestine. [1]	1
1(d)	They are absorbed in the small intestine and carried in the blood. Absorbed in the small intestine [1] Carried in the blood [1]	2
	Total for Question 1	5
2(a)	Carbohydrases for the rice, proteases for the chicken, and lipases for the oil. Carbohydrases for rice / carbohydrate [1] Proteases for chicken / protein [1] Lipases for oil / fat [1]	3
2(b)	It churns the food and adds acid. Churns / mixes the food [1] Adds acid [1]	2
	Total for Question 2	5
3(a)	Digestion breaks large molecules into smaller ones. Absorption is the movement of those small molecules into the blood. Digestion breaks molecules down [1] Absorption moves the products into the blood [1]	2
3(b)	Egestion removes undigested food, for example through the anus. Excretion removes waste made by the body, for example carbon dioxide from the lungs. Egestion is undigested food, with an example [1] Excretion is waste the body produced, with an example [1]	2
3(c)	It absorbs water. [1]	1
	Total for Question 3	5
4(a)	The lining of the intestine lets small molecules through. Large molecules such as starch cannot pass into the blood. Large molecules cannot pass into the blood [1] Digestion makes them small enough [1]	2
4(b)	Less water is left in the remains, or the remains stay dry, so they are harder to egest. Less water in the remains / remains are dry [1] Egestion is more difficult [1]	2
4(c)	Any one: regular physical activity; a diet that is not high in sugar. Regular activity or a diet that is not high in sugar [1]	1
	Total for Question 4	5

— End of mark scheme —