O LevelBiologyCambridgeTopic Questions9. Human Gas Exchange9.1 Human Gas Exchange

Human Gas Exchange (Cambridge O Level Biology)

Topic Questions

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1
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What makes the alveoli suitable as a gas exchange surface in mammals?

 

a dense capillary network

large total surface area
A X X
B ✓ X
C X ✓
D ✓ ✓

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2
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Which of the following sequences show the correct path of oxygen as it enters the lungs?

  • trachea → bronchiole → bronchus → alveolus

  • trachea → bronchus → bronchiole → alveolus

  • alveolus → bronchus → bronchiole → trachea

  • alveolus → bronchiole → bronchus → trachea

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3
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What is the approximate percentage of carbon dioxide in expired air?

  • 16 %

  • 0.04 %

  • 4 %

  • 21 %

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4
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The image below shows some cells found in the trachea.

11--image-8-ciliated-cells

What is the function of the part labelled K?

  • Increasing surface area

  • Gas exchange

  • Moving mucus

  • Trapping bacteria

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5
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Name the structures shown in the diagram.

lungs

  W X Y Z
A larynx trachea bronchi bronchioles
B trachea  larynx bronchioles bronchi
C bronchi trachea bronchioles larynx
D larynx bronchi larynx bronchioles

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61 mark

What is the approximate percentage of carbon dioxide in expired air released by a human?

  • 0.04%

  • 0.4%

  • 4.0%

  • 14%

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1
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Which of the following correctly describes the actions of the intercostal muscles and the diaphragm when we breathe in?

  external intercostal muscles internal intercostal muscles diaphragm

A

 contract relax domed

B

 contract relax flat

C

 relax contract domed

D

 relax contract flat

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2
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The diagram shows part of the structure of a human lung.

Where would the concentration of carbon dioxide be highest?

11--image-3-alveolus11--image-3-alveolus

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3
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The diagram below illustrates the changes in air pressure taking place inside the lungs during a complete cycle of breathing. Atmospheric pressure is 101 kPa.

11--image-1-pressure-in-the-lungs

At which point on the diagram does the process of inhalation start?

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4
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A person exhales, and the air from their lungs is collected and placed in a gas jar. A second gas jar contains normal atmospheric air. A candle is set alight and is placed inside each gas jar as shown. The time taken for each flame to go out is measured with a stopwatch.

-11--image-7-gas-jars

The table shows the results of this experiment.

gas jar

time for candle flame to go out /s
1 7
2 12

Which of the following is a correct explanation for the difference between the results in jars 1 and 2?

  • Jar 1 contains atmospheric air which has less oxygen than exhaled air.

  • Jar 1 contains exhaled air which has less oxygen compared to atmospheric air.

  • Jar 2 contains atmospheric air which has more carbon dioxide than exhaled air.

  • Jar 2 contains exhaled air which has more carbon dioxide than oxygen in it.

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5
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Which of the following helps carbon dioxide to be excreted rapidly into the alveoli from the blood in the lungs?

  1. Inhaled air has a lower concentration of carbon dioxide than the blood constantly pumping through the lungs.
  2. Alveoli have thick walls and a large surface area.
  3. Alveoli have thin walls and a large surface area.
  4. The concentration of carbon dioxide in the blood is lower than in the alveoli.

  • 1, 2 & 4 only

  • 3 only

  • 1 & 3 only

  • 3 & 4 only

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6
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The graph shows changes in the volume of air in the lungs of a person at rest, over a period of 30 seconds.

-11--image-4-air-in-lungs

Which graph below shows the changes in the volume of air in the lungs for the same person immediately after they have done a few minutes of vigorous exercise?

11--image-5-breathing-rate

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1
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The diagram below shows a cross-section through an alveolus and a capillary.

11--image-6-alveolus-and-capillary

Why does oxygen move from P to Q?

  • The concentration of carbon dioxide is lower in the alveolus than in the blood.

  • The concentration of oxygen in the blood is lower than in the air in the capillary.

  • Oxygen must replace carbon dioxide.

  • The concentration of oxygen in the blood is lower than the air in the alveolus.

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2
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Some amphibians, such as frogs, can use their skin as a gas exchange surface.

What are the most likely characteristics of the surface of the skin in these amphibians?

  surface area type of skin
A small thick
B large thick
C small thin
D large thin

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3
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When the diaphragm relaxes and internal intercostal muscles contract, how does the volume and pressure inside the thorax change?

  pressure volume
A decreases decreases
B decreases increases
C increases decreases
D increases increases

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4
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Compared to the composition of atmospheric air, the air exhaled by a man contains:

  • more water vapour, more carbon dioxide.

  • more water vapour, less carbon dioxide.

  • less water vapour, more carbon dioxide.

  • less water vapour, less carbon dioxide.

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5
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The diagram shows the composition of four samples of air (O2 = oxygen, CO2 = carbon dioxide, N2 = nitrogen).

11--image-2-composition-of-air

Which sample is inspired air and which sample is expired air?

  inspired air expired air
A R S
B P R
C Q P
D S R

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61 mark

Why does oxygen enter the blood in the lungs?

  • Aerobic respiration takes place in the lungs.

  • Carbon dioxide diffuses out of the blood into the alveoli.

  • The air in alveoli contains a higher concentration of oxygen than the blood in the lung capillaries.

  • The air in alveoli contains a lower concentration of oxygen than the blood in the lung capillaries.

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