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IGCSE Biology - Extended > 11 Gas Exchange in Humans > Flashcards

11 Gas Exchange in Humans Flashcards

1
Q

Are gas exchange systems in all animals the same?

A

NO
The surfaces where gas exchange occurs in an organism are very different and different organisms have evolved different mechanisms for getting the gases to the gas exchange surface depending on size, where they live etc.

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2
Q

What do gas exchange features allow?

A

These features allow the maximum amount of gases to be exchanged across the surface in the smallest amount of time

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3
Q

What are the 4 main features of gas exchange surfaces?

A

Large surface area
Thin walls
Good ventilation with air
Good blood supply

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4
Q

How is a large surface area useful?

Gas Exchange Surfaces

A

to allow faster diffusion of gases across the surface

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5
Q

How are thin walls useful?

Gas Exchange Surfaces

A

to ensure diffusion distances remain short

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6
Q

How is a good ventilation with air useful?

Gas Exchange Surfaces

A

so that diffusion gradients can be maintained

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7
Q

How is a good blood supply useful?

Gas Exchange Surfaces

A

to maintain a high concentration gradient so diffusion occurs faster

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8
Q

Name the 8 structures of the respiratory system

A 
ribs
intercostal muscle
diaphragm
trachea
larynx
bronchi
bronchioles
alveoli
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9
Q

Ribs definition

A

bone structure that protects internal organs such as the lungs

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10
Q

intercostal muscle definition

A

Muscles between the ribs which control their movement causing inhalation and exhalation

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11
Q

Diaphragm definition

A

Sheet of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation

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12
Q

Trachea definition

A

Windpipe that connects the mouth and nose to the lungs

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13
Q

Larynx definition

A

Also known as the voice box, when air passes across here we are able to make sounds

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14
Q

Bronchi definition

A

Large tubes branching off the trachea with one bronchus for each lung

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15
Q

Bronchioles definition

A

Bronchi split to form smaller tubes called bronchioles in the lungs connected to alveoli

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16
Q

Alveoli definition

A

Tiny air sacs where gas exchange takes place

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17
Q

Why must there be two sets of intercostal muscles?

A

Muscles are only able to pull on bones, not push on them

This means that there must be two sets of intercostal muscles; one to pull the rib cage up and another set to pull it down

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18
Q

Where are the external intercostal muscles found?

A

One set of intercostal muscles is found on the outside of the ribcage (the external intercostal muscles)

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19
Q

Where are the internal intercostal muscles found?

A

The other set is found on the inside of the rib cage (the internal intercostal muscles)

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20
Q

What structure surrounds the trachea and bronchi?

A

Rings of cartilage surround the trachea (and bronchi)

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21
Q

Why are there rings of cartilage surrounding the trachea and bronchi?

A

The function of the cartilage is to support the airways and keep them open during breathing

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22
Q

What would happen if the rings of cartilage were not present around the trachea and bronchi?

A

If they were not present then the sides could collapse inwards when the air pressure inside the tubes drops

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23
Q

What are the passages down to the lungs lined with?

A

The passages down to the lungs are lined with ciliated epithelial cells

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24
Q

What do cilia do?

A

these cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed

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25
Q

Where is mucus made?

A

The mucus is made by special mucus-producing cells called goblet cells

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26
Q

What is the role of the mucus?

A

The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents them getting into the lungs and damaging the cells there

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27
Q

Describe the role of cilia and mucus

A
  1. The mucus is produced by goblet cells and traps bacteria, dust, particles
  2. The cilia beat
  3. And push the mucus away from the lungs towards the throat
    3 marks
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28
Q

WHat is the diaphragm responsible for?

A

it is ultimately responsible for controlling ventilation in the lungs

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29
Q

What happens during inhalation?

A
  • external intercostal muscles contract (pulls ribs)
  • ribcage moves up and out
  • diaphragm contracts and flattens
  • volume of thorax increases
  • air pressure inside thorax decreases relative to outside the body
  • air is drawn in
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30
Q

What happens during exhalation?

A
  • external intercostal muscles relax
  • ribcage moves down and in
  • diaphragm relaxes and becomes dome-shaped
  • volume of thorax decreases
  • air pressure inside thorax increases relative to outside the body
  • air is forced out
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31
Q

In what way do the the intercostal muscles work together?

A

The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)

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32
Q

What happens when we need to increase the rate of gas exchange? What is this called

A

When we need to increase the rate of gas exchange (for example during strenuous activity) the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly – this is called forced exhalation

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33
Q

Why is forced exhalation needed?

A

There is a greater need to rid the body of increased levels of carbon dioxide produced during strenuous activity and to inhale more oxygen

This allows a greater volume of gases to be exchanged

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34
Q

Does inspired and expired air have a different amount of gases? Why?

A

YES
Air that is breathed in and air that is breathed out has different amounts of gases in it due to exchanges that take place in the alveoli

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35
Q

How much oxygen does atmospheric air have?

A

Atmospheric air contains around 20 – 21% oxygen

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36
Q

How much oxygen from atmospheric air do we absorb? How much do we exhale?

A

we only absorb around 4 – 5%, breathing out air containing around 16% oxygen

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37
Q

How much CO2 does atmospheric air have?

A

Normal carbon dioxide content of air is around 0.04%

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38
Q

How much CO2 is in expired air?

A

As carbon dioxide diffuses into the alveoli from the blood, we breathe out air containing around 4% carbon dioxide

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39
Q

What other substance, apart from O2 and CO2, do we expire?

A

The air we breathe out contains more water vapour than when we breathe it in

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40
Q

What is also different about expired air, apart from its gas content?

A

the temperature of exhaled air is higher than inhaled air

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41
Q

Why is the oxygen content in expired and inspired air different?

A

oxygen is removed from blood by respiring cells so blood returning to lungs has a lower oxygen concentration than the air in the alveoli which means oxygen diffuses into the blood in the lungs

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42
Q

Why is the carbon dioxide content in expired and inspired air different?

A

carbon dioxide is produced by respiration and diffuses into blood from respiring cells: the blood transports the carbon dioxide to the lungs where it diffuses into the alveoli as it in a higher concentration in the blood than in the air in the alveoli

43
Q

Why is the water vapour content in expired and inspired air different?

A

water evaporates from the moist lining of the alveoli into the expired air as a result of the warmth of the body

44
Q

Why is the nitrogen content in expired and inspired air different?

A

THERE IS NO DIFFERENCE -78%

nitrogen gas is very stable and so cannot be used by the body, for this reason its concentration does not change in inspired or expired air

45
Q
  1. What substance can be used to test for CO2?
A

Limewater

46
Q
  1. Using a setup of two test tubes, containing limewater and connected by rubber tubing, how could you test the content of CO2 in expired air?
A

When we breathe in, the air is drawn through boiling tube A

When we breathe out, the air is blown into boiling tube B

47
Q
  1. What change in the limewater would you see during this experiment?
    (Using Limewater to Test for CO2 in Exhaled Air)
A

Lime water is clear but becomes cloudy (or milky) when carbon dioxide is bubbled through it
The lime water in boiling tube A will remain clear, but the limewater in boiling tube B will become cloudy

48
Q
  1. What does this experiment show us?

Using Limewater to Test for CO2 in Exhaled Air

A

This shows us that the percentage of carbon dioxide in exhaled air is higher than in inhaled air

49
Q

What is the effect of exercise on breathing?

A

Exercise increases the frequency and depth of breathing

50
Q
  1. How can you Investigate the Effect of Exercise on Breathing?
A
  • This can be investigated by counting the breaths taken during one minute at rest and measuring average chest expansion over 5 breaths using a tape measure held around the chest
  • Exercise for a set time (at least 3 minutes)
  • Immediately after exercising, count the breaths taken in one minute and measure the average chest expansion over 5 breaths
51
Q
  1. What will be the results of this experiment? (Investigating the Effect of Exercise on Breathing)
A

Following exercise, the number of breaths per minute will have increased and the chest expansion will also have increased

52
Q
  1. Why does frequency and depth of breathing increase when exercising?
A

This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them (and carbon dioxide removed) to keep up with the energy demand

53
Q
  1. What happens if, during exercise, the muscles cannot receive enough nutrients?
A

If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid

54
Q
  1. Why does lactic acid need to be removed?
A

After exercise has finished, the lactic acid that has built up in muscles needs to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions

55
Q
  1. How can lactic acid be removed?
A

It can only be removed by combining it with oxygen – this is known as ‘repaying the oxygen debt’

56
Q
  1. How can the time taken for a person to repay their oxygen debt be investigated?
A

This can be tested by seeing how long it takes after exercise for the breathing rate and depth to return to normal – the longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid

57
Q
  1. What increases in amount during exercise?
A

As respiration rates increase, more carbon dioxide is produced and enters the blood

58
Q
  1. Why is carbon dioxide harmful?
A

Carbon dioxide is an acidic gas in solution and so it can affect the working of enzymes in the cells and needs to be removed as quickly as possible

59
Q
  1. How are high carbon dioxide levels detected?
A

As blood flows through the brain, the increase in carbon dioxide concentration stimulates receptor cells

60
Q
  1. What happens once the receptor cells have detected the high levels of CO2?
A

These send impulses to the muscles of the lungs, causing them to contract faster and more strongly

61
Q
  1. What does the lungs contracting faster and stronger do to CO2 levels?
A

This causes the frequency and depth of breathing to increase until the carbon dioxide concentration of the blood has lowered sufficiently

62
Q

Respiration definition

A

Respiration is a chemical process that involves the breakdown of nutrient molecules (specifically glucose) in order to release the energy stored within the bonds of these molecules

63
Q

In what two ways can respiration take place and what does this mean?

A

Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically

64
Q

Why is aerobic respiration more effective than anaerobic respiration?

A

Much less energy is released for each glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically

65
Q

Where does respiration take place?

A

Respiration occurs in all living cells. Most of the chemical reactions in aerobic respiration take place in the mitochondria

66
Q

List 7 reasons why energy from respiration is needed

A
  • Contract muscle
  • Synthesise proteins
  • Cell division (to make new cells)
  • Grow
  • Enable active transport to take place
  • Allow nerve impulses to be generated
  • Maintain a constant internal body temperature
67
Q

How is respiration controlled?

A

Respiration is a series of reactions that are controlled by enzymes

68
Q

Aerobic respiration definition

A

Aerobic respiration requires oxygen and is defined as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy

69
Q

Does aerobic respiration break down glucose molecules completley?

A

YES

It is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes

70
Q

What does aerobic respiration produce?

A

It produces carbon dioxide and water as well as releasing useful cellular energy

71
Q

Write the chemical equation for respiration

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O

72
Q
  1. How can we investigate oxygen uptake by respiring organisms?
A

We can investigate aerobic respiration in living organisms by measuring the amount of oxygen that they take from the air
This is done by measuring the change in volume in an enclosed tube containing the organisms

73
Q
  1. What is one problem with this experiment? How can it be solved?

Investigating Uptake of Oxygen by Respiring Organisms

A

However, as they respire the organisms release carbon dioxide, which increases the gas volume
The carbon dioxide must therefore be removed from the tube using a chemical

74
Q
  1. What chemicals can be used to remove carbon dioxide?

Investigating Uptake of Oxygen by Respiring Organisms

A

soda lime or sodium hydroxide

75
Q
  1. What organisms can be used in this experiment?

Investigating Uptake of Oxygen by Respiring Organisms

A

Any small organisms can be used in the apparatus, including seeds or arthropods

76
Q
  1. What is the apparatus used in this experiment known as?

Investigating Uptake of Oxygen by Respiring Organisms

A

The apparatus is known as a respirometer

77
Q
  1. What does a respirometer consist of?

Investigating Uptake of Oxygen by Respiring Organisms

A

The apparatus consists of two tubes, one containing the living organisms and the other with glass beads to act as a control

78
Q
  1. What is monitored during the experiment?

Investigating Uptake of Oxygen by Respiring Organisms

A

Once the apparatus has been set up, the movement of the coloured liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration

79
Q
  1. What causes the liquid in the tube to move?

Investigating Uptake of Oxygen by Respiring Organisms

A

The reduction of volume in the tube increases pressure causing the coloured liquid to move

80
Q
  1. What will the distance moved by the liquid provide?

Investigating Uptake of Oxygen by Respiring Organisms

A

The distance moved by the liquid in a given time is measured will provide the volume of oxygen taken in by the insect per minute

81
Q
  1. What is a control?

Investigating Uptake of Oxygen by Respiring Organisms

A

A control is a duplicate experiment set up with the condition being investigated having been removed or neutralised in some way.

82
Q
  1. How is a control used in this experiment?

Investigating Uptake of Oxygen by Respiring Organisms

A

As they are not alive, they will definitely not be respiring. If the volume of oxygen decreases in the tube with the glass beads during the course of the experiment, then we know that the condition being investigated (respiration in living organisms) is not the cause of it.

83
Q
  1. What is the overall use of a control?

Investigating Uptake of Oxygen by Respiring Organisms

A

A control helps to make your experiment valid.

84
Q
  1. How can this experiment be modified to investigate the effect of temperature on the rate of respiration?

Investigating the Effect of Temperature on the Rate of Respiration

A

To investigate the effect of temperature on the rate of respiration of germinating seeds the respirometer can be set up and the tubes submerged in a series of water baths set at different temperatures, eg 10℃, 15℃, 20℃, 25℃, 30°C

85
Q
  1. What must be done to the seeds before the experiment starts?

Investigating the Effect of Temperature on the Rate of Respiration

A

The seeds should be kept in the water bath for 15 minutes before the start of the experiment to ensure they have acclimated to the temperature

86
Q
  1. Why is a temperature not higher than 40 degrees used?

Investigating the Effect of Temperature on the Rate of Respiration

A

As respiration is an enzyme controlled reaction, it is unlikely to work faster beyond around 40℃ as the enzymes will denature

87
Q

Anaerobic respiration definition

A

Anaerobic respiration does not require oxygen and is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen

88
Q

Does anaerobic respiration break down glucose completely?

A

NO

It is the incomplete breakdown of glucose and releases a relatively small amount of energy for use in cell processes

89
Q

What type of products does anaerobic produce?

A

It produces different breakdown products depending on the type of organism it is taking place in

90
Q

When does anaerobic respiration mainly take place?

A

Anaerobic respiration mainly takes place in muscle cells during vigorous exercise

91
Q

Why does anaerobic respiration mainly take place when we exercise?

A

When we exercise vigorously, our muscles have a higher demand for energy than when we are resting or exercising normally. Our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration

92
Q

What is a product of anaerobic respiration in animals and why?

A

as much glucose as possible is broken down with oxygen, and some glucose is broken down without it, producing lactic acid instead

93
Q

Why is less energy released during anaerobic respiration?

A

There is still energy stored within the bonds of lactic acid molecules that the cell could use; for this reason, less energy is released when glucose is broken down anaerobically

94
Q

What is the word equation for anaerobic respiration in animals?

A

glucose —> lactic acid

95
Q

What does lactic acid do in muscle cells?

A

Lactic acid builds up in muscle cells and lowers the pH of the cells (making them more acidic)

96
Q

Why is lactic acid harmful when it builds up?

A

This could denature the enzymes in cells so it needs to be removed

97
Q

Where do cells excrete lactic acid into?

A

Cells excrete lactic acid into the blood

98
Q

Once in the blood, where does lactic acid go and what happens to it?

A

When blood passes through the liver, lactic acid is taken up into liver cells where it is oxidised, producing carbon dioxide and water

99
Q

What process is occuring when lactic acid is being oxidised in the liver?

A

Lactic acid reacts with oxygen – this is actually aerobic respiration with lactic acid as the nutrient molecule instead of glucose

100
Q

What are the waste products of lactic acid oxidation?

A

So the waste products of lactic acid oxidation are carbon dioxide and water

101
Q

Why do we keep breathing heavily after exercise?

A

This is the reason we continue to breath heavily and our heart rate remains high even after finishing exercise – we need to transport the lactic acid from our muscles to the liver, and continue getting larger amounts of oxygen into the blood to oxidise the lactic acid
This is known as ‘repaying the oxygen debt’

102
Q

Why is anaerobic respiration in yeast useful and how do we take advantage of it?

A

We take advantage of the products of anaerobic respiration in yeast by using it in bread making (where the carbon dioxide produced helps dough to rise) and in brewing (where the ethanol produced makes beer)

103
Q

What is the word equation for anaerobic respiration in yeast?

A

glucose —> alcohol + carbon dioxide

104
Q

What is the chemical equation for anaerobic respiration in yeast?

A

C6H12O6 —> 2C2H5OH + 2CO2

IGCSE Biology - Extended (22 decks)

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