Question 1.3 [10 marks]

Question

Indicate whether each of the descriptions in Column I applies to A ONLY, B
ONLY, BOTH A and B or NONE of the items in Column II. Write A only, B only,
both A and B or none next to the question number.
Column I Column II
1.3.1 Organisms that are able to make their own
food.
A: Heterotrophs
B: Autotrophs
1.3.2 Elimination of undigested food, usually via
defecation.
A: Egestion
B: Ingestion
1.3.3 Teeth for biting off pieces of food and for
cutting.
A: Canines
B: molars
1.3.4 Feelings of worry or tension that are caused
by a difficult situation.
A: Depression
B: Anxiety
1.3.5 Molecule that consists of two phosphate
groups.
A: ATP
B: ADP
TOTAL: [2 x 5 = 10]
Question 1.4 [10 marks]
The air in the atmosphere is made up mainly of nitrogen, oxygen, carbon dioxide
water vapour and traces of inert gases. Inhaled air has the same composition as
atmospheric air but is different to exhaled air. Figure 3 below shows the
9
difference in composition of the three main gases after exercise and while
sleeping.
Gas Inhaled air
(%)
Exhaled air (%)
from a sleeping
person
Exhaled air (%)
from a person
exercising
Nitrogen(N₂) 78 78 78
Oxygen(O₂) 21 15 11
Carbon dioxide(CO₂) 0.04 3 10
Figure 3: The composition of inhaled and exhaled air
Nitrogen is not used in the human breathing system. Oxygen is used by the cells
in cellular respiration and carbon dioxide is a product of cellular respiration and
needs to be removed from the cells.
Question 1.4.1 [2 marks]
What is the difference between the percentage of oxygen inhaled and that
exhaled by a sleeping person?
Question 1.4.2 [2 marks]
What is the percentage of oxygen used by the body in each inhalation of a
person who is exercising?
Question 1.4.3 [4 marks]
State whether there is a DECREASE or INCREASE or NO CHANGE in exhaled air
from a sleeping person and an exercising person in the following gases:
a. Oxygen (1)
b. Carbon dioxide (2)
c. Nitrogen (1)
Question 1.4.4 [2 marks]
Which other component of air is not included in the table above?
1

Answer 1

Question 1.3

1.3.1 Organisms that are able to make their own food.
Answer: B only (Autotrophs)

1.3.2 Elimination of undigested food, usually via defecation.
Answer: A only (Egestion)

1.3.3 Teeth for biting off pieces of food and for cutting.
Answer: A only (Canines)

1.3.4 Feelings of worry or tension that are caused by a difficult situation.
Answer: B only (Anxiety)

1.3.5 Molecule that consists of two phosphate groups.
Answer: B only (ADP)

TOTAL: [2 x 5 = 10]

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Question 1.4

Question 1.4.1 [2 marks]

What is the difference between the percentage of oxygen inhaled and that exhaled by a sleeping person?
Answer: The difference is 6% (21% inhaled - 15% exhaled = 6%).

Question 1.4.2 [2 marks]

What is the percentage of oxygen used by the body in each inhalation of a person who is exercising?
Answer: The percentage of oxygen used is 10% (21% inhaled - 11% exhaled = 10%).

Question 1.4.3 [4 marks]

State whether there is a DECREASE or INCREASE or NO CHANGE in exhaled air from a sleeping person and an exercising person in the following gases: a. Oxygen
Answer: DECREASE

b. Carbon dioxide
Answer: INCREASE

c. Nitrogen
Answer: NO CHANGE

Question 1.4.4 [2 marks]

Which other component of air is not included in the table above?
Answer: Water vapour (H₂O)