This document contains answers to objective and structured questions about digestion, nutrition, and respiration. It provides the answers to 20 multiple choice questions about digestion. The structured questions cover topics like the components of food, the role of roughage in digestion, and comparing the daily protein requirements of children and teenage boys. The essay questions discuss the meanings of digestion and absorption, the enzymes involved in pancreatic juice, and the differences between aerobic and anaerobic respiration. Pathways of gas exchange in humans and plants are also outlined.

1. Answers
Objective Questions
1C
2D
3D
4C
5D
/r
7B
8B
9A
10D
11 C
12C
13D
t4A
lsB
168
178
18C
19B
20A
2tA
22B
23D
24D
251'
Structured Questions
1 (a) (i) Protein
(ii) Carboh-1-drate
(iii) 100% - (62.4 t 7 *'t i.q%- 100% - 80.4% = 19.60/o
(b) Roughage
The roughage stimulates peristalsis and prevents the stool from becoming hard.
(c) 1 Alkaline characteristics - prepares a medium that is suitable for enzl-matic
action
2 Acts as the fat emulsif ing agent
(d) The action of the lipase produces fatfy- acid- ivtich has acidic characteristics to
neutralise the alkaline condition of the mixlure in the test tube
(e) Packaged milk because its digested producis take a longer time to neutralise the
contents ofthe test tube
2 (:a) (i) Teenage boys are nearl-v at the end of ..'heir bone and teeth gror,vth compared
with children who need more vitamin D to help in calcium absorption for
the formation of strong bone and teeth.
(ii) Teenage boys are more active compared with children; as such teenage
boys need more iron nutrients to build haemoglobin for oxygen transport
to the muscle for energy release.
(iii) Teenage girls experience menstruation every month. As such, they require
more iron nutrients than teenage boys, to replace the loss of blood.
(bxi) Dailv protein requirement per kg of bodv mass
+,
i- ).1 Jlrs
(ii) Daily protern requrement per ks of bodv mass
q '' isilr4'
T6
-J

2. (c) (i) Children require twjce the amount of protein compared with teenage boys
because children are in the a stage of active growth, where protein is
required to build new cells, while teenage boys only require protein to repair
damaged tissues onl1,.
(i1) Meat/soya bean contains all the required amino acids. Eating one type of
vegetable will not provide all the required amino acids.
(d) 1 Roughage
2 Water
Essay Question
(a) The meaning offood digestion - Break up / hydrolyse big and complex food
molecules into small and simple molecules through the action of enzymes.
The meaning of food absorption - Small and digestecl food molecules diffuse
from inside the intestine into the blood vessels
(b) Pancreas secretes pancreaticjuice that has alkaline properties in order to prepare a
suitable medium for enzymatic action. Pancreatic juice contains (i)
-
amylase
elzvme that acts on the starch to produce maltose, (ii) lipase enzyme that acts on
the fat to produce fattl'- acids and glycerol. (iii) trypsin enzyme that hydrolyses
peptone and polvpeptide into peptides.
(c) Hypothesis: Young mice is grven vitamins in their rnilk grow faster than young
mice that are not given this nutrition.
Plan of experiment:
Number of mice: 25 - 30 mice per group
Create tu'o groups.
Group 1: Gven milk contairung vitamins
Group 2: Gven milk rvithout vitamins
Variable that: is manipulated - vitamin content in the milk; responds - increase in
the growth rate (measured in mass). are kept constant - species, age, sex,
sun'oundings, and milk qualit-v
l0

3. Answers
I
2
3
4
5
6
7
8
Objective Questions
A
B
C
D
C
B
D
C
2 (i)
branched
9A
10c
11 A
12D
13D
14D
15B
t6B
body cell
Structured Questions
1 (a) To control the alr temperature in test tubes p and e so that it is at 25"c
(b) Woodlice breathes by absorbing oxygen and releasing carbon dicxide. Carbon
dioride is absorbed b1- the potassium hvdroxide solution causing the air pressure in
test tube P to decrease and become lower than the air pressure in test tube Q. As
such, the level of the manometer liquid rises in the arm that is connected to test tube
(c) The level of the manometer liquid rises higher because the rate of oxvgen intake in
the cockroach is faster than in the woodlice.
(d)
Facheole
(b) (i) Atmospheric carbon dioxide content is lower compared with the air that is
breathed out
(ii) The breathing rate increases after carr5,ing out physical activities an,J the rate of
carbon dioxide release increases
Breathine out Breathrins irr
FlaskA None Air bubbles
Flask B Air bubbles None

4. Essay Question
(a) (i) Anaerobic respiration is the breakdown of glucose in the absence of orygen - This
process occurs in yeast and certain bacteria
(it) The differences between anaerobic respiration and aerobic respiration:
1 In anaerobic respiration, glucose is not fully broken down, and part of the energy
is still stored in the ethanol molecule - As such. the energi, released from
anaerobic respiration differs little from aerobic respiration.
2 Anaerobic respiration does not require oxi'gen compared i,l'ith aerobic respiration
that requires o,V-gen.
3 The product of glucose decomposition from anaerobic respiration is ethanol/lactic
acid. This is different from the products in aerobic respiration, whrch ale carbon
dioxide and ,vater.
(b)
Pathwav Method of transportation
Nose, Phary.nx. Larynx. Trache4
Bronchus. Bronchiole
Breathins in
Alveolus to the blood capillan Diffusion
Venule- pulmonarv vein- heart Unidirectional blood circulation guided by
the crescent valve in the vein
Carbon dioxi<ie gas molecules breathed out b1'humans ) atmosphere ) diffusion )
enters the leaf through the stoma opening ) diffusion in the arr spaces betu.een the
sponge mesophy'll cells ) enters the mesoph-vll cell ) photosynthetrc process in the
mesoph-vll ceil ) dark stage ) carbon ciioxide is reduced by hydrogento form glucose
(c)