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AQA A level Biology > 3.2 Gas exchange > Flashcards

3.2 Gas exchange Flashcards

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1
Q

Do single-celled organisms have a small or large SA: Vol ratio

A

Large

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2
Q

In single-celled organisms how is oxygen absorbed

A

By diffusion across their body surface, which is covered only by a cell-surface membrane

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3
Q

How have insects evolved for gas exchange

A

Have evolved an internal network of tubes called tracheae

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4
Q

What is the tracheae supported by

A

Strengthened rings which prevent them from collapsing

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5
Q

What is the name of the smaller dead-end tubes that the tracheae divides into

A

Tracheoles

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6
Q

Why are tracheoles useful

A

As they extend throughout all the body tissues of the insect, meaning oxygen and other atmospheric gases are brought directly to the respiring tissues

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7
Q

What are the 3 ways in which respiratory gases move in and out of the tracheal system

A
  • Along a diffusion gradient
  • Mass transport
  • The ends of the tracheoles are filled with water
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8
Q

How does mass transport help respiratory gases to move in and out of the tracheal system in insects

A

The contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out which further speeds up the exchange of respiratory gases

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9
Q

What are the 3 parts of an insect that the body is divided into

A
  • Head
  • Thorax
  • Abdomen
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10
Q

What type of bodies do insects have

A

Segmented

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11
Q

How many spiracles does each segment of an insect have

A

2 spiracles (openings)

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12
Q

What do spiracles contain

A

Valves

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13
Q

Why are the valves in spiracles useful

A

As they reduce water loss as they can open and close

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14
Q

What are tracheal tubes lined with

A

Chitin

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15
Q

What does tracheal tubes being lined with chitin do to the tubes

A

Provides structural support

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16
Q

What does the tracheal tube branch into

A

Tracheoles

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17
Q

What do tracheoles provide

A

A large surface area

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18
Q

What is the site of gas exchange in insects

A

The tracheoles

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19
Q

What are tracheoles lined with and how it is beneficial

A

Lined with fluid in the tips so gases can dissolve so can diffuse easier

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20
Q

How is a short diffusion pathway created in insects

A

As the tracheole tubes contact every single tissue

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20
Q

What don’t insects synthesise since the tracheoles contact every single tissue

A

Haemoglobin since blood doesn’t transport oxygen

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21
Q

Why do insects have an internal respiratory system

A

It reduces water loss

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22
Q

What type of ventiliation (tidal or unidirectional) do insects have. And what spiracles does air go in and out of

A

Unidirectional as the air is sucked into the thorax spiracles and out of the abdomen spiracles

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23
Q

When an insects’ abdomen expands what happens to the internal pressure and volume and what happens to the air

A

Pressure decreases while the volume increases. Since air flows down a pressure gradient air is sucked in

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24
Q

When an insects’ abdomen contracts what happens to the internal pressure and what happens to the air

A

Pressure increases which pushes air outwards

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25
Q

What is the SA:Vol ratio like in fish

A

Relatively small

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26
Q

What does the small SA:Vol ratio in fish mean they can’t do

A

They can not simply diffusion gases

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27
Q

What is the specialised internal gas exchange surface in fish

A

The gills

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28
Q

Where are the gills located in fish

A

Behind the head

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29
Q

What are the gills made up of

A

Gill filaments

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30
Q

What are positioned at right angles to the gill filaments

A

Gill plates

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31
Q

How many layers of gills are on either side of the head

A

4 layers

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32
Q

How are the gill filaments placed together

A

They are stacked

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33
Q

What increases the surface area in the gills

A
  • Having stacks of gill filaments that are covered in gill plates
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34
Q

What is the gas exchange surface in the fish

A

The gill plates

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35
Q

What happens once the fish opens its mouth and water is taken in

A

The water is FORCED over the gills and out through an opening on each side of the body

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36
Q

What does counter-current flow mean

A

Water flows over the gills in the opposite direction to the flow of blood in the capillaries

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37
Q

Why is a counter-current flow useful

A

Since a diffusion gradient for oxygen is maintained across the entire width of the gill plate

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38
Q

In relation to fish gills, describe what is meant by counter-current flow

A

The movement of water and blood in opposite directions across the gill plate

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39
Q

Outline why counter-current flow is an efficient means of exchanging gases across the gills of fish

A

Because a steady diffusion gradient is maintained over the entire length of the gill plate. Therefore more oxygen diffuses from the water into the blood

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40
Q

Mackerel are active, fast-swimming fish while plaice spend most of their lives moving slowly on the sea bed. There are differences in the gills of these 2 types of fish. Suggest what these differences might be

A

Mackerel have more gill plates/ gill filaments/ larger SA compared to plaice

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41
Q

Water flow over fish gills is one-way whereas the flow of air in and out of the lungs is 2-way. Suggest why one-way flow is an advantage to fish

A

Less energy is required because the flow does not have to reversed (important as water is dense and difficult to move)

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42
Q

Name the process by which carbon dioxide is removed from single-celled organism

A

Diffusion over the body surface

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43
Q

Explain why there is a conflict in terrestrial insects between gas exchange and conserving water

A

Gas exchange requires a thin permeable surface with a large area. Conserving water requires thick, waterproof surfaces with a small area

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44
Q

Explain how the tracheal system limits the size of insects

A

Because it relies on diffusion to bring in oxygen to the respiring tissues. If insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply their needs

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45
Q

In mammals, what is their evolved gas exchange organ

A

Lungs

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46
Q

In humans/ mammals what is the gas exchange surface

A

Alveoli

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47
Q

In humans what area is classed as the thorax

A

From the diaphragm to the clavicle

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48
Q

What 3 things protect the lungs

A
  • Ribcage
  • Diaphragm
  • Sternum
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49
Q

What type of ventilation do mammals have

A

Tidal

50
Q

What happens to the air in the nasal cavity

A

It is warmed and moistened

51
Q

Why is it beneficial for the air to be warmed and moistened in the nasal cavity before it goes to the lungs

A

So the gases can dissolve so there’s more efficient gas exchange

52
Q

Where does the air go after it has entered the nasal cavity

A

Down the trachea and into the lungs

53
Q

What is the trachea supported by

A

C-Shaped cartilage

54
Q

Why is the cartilage that supports the trachea c-shaped

A

As it makes the trachea flexible so when we swallow food the food can go down

55
Q

Why does the trachea need to be supported

A

So it does not collapse during breathing in

56
Q

What is the name of the 2 branches at the end of the trachea

A

Bronchi (left and right bronchus)

57
Q

What is the trachea lined with

A

Ciliated epithelial cells

58
Q

What type of cell lines the trachea and what does it do

A

Goblet cells and these secrete mucus (mucus is made there and is released there)

59
Q

What happens to the amount of cartilage as the bronchi get smaller

A

The amount decreases

60
Q

What is the name of the branching subdivisions of the bronchi called

A

Bronchioles

61
Q

What are the wall of the bronchioles made of

A

Muscle lined epithelial cells

62
Q

What does the muscle in the bronchioles do

A

It allows the bronchioles to constrict so they can control the flow of air in and out of the alveoli

63
Q

What is the name of the air sacs at the end of the bronchioles

A

Alveoli

64
Q

What are the 5 traits of the alveoli

A
  • Moist
  • Thin
  • Good blood supply- maintains concentration gradient
  • Permeable to gas
  • Has a large surface area
65
Q

What is the name of the membrane that lines the chest cavity and surrounds each lung

A

Pleural membrane

66
Q

What does the pleural fluid do

A

It reduces friction when the lungs expand and relax since it acts as a lubricant

67
Q

What is the difference between adhesive and cohesive

A

Adhesive- means it sticks to something else
Cohesive- means it sticks to itself

68
Q

Is the pleural fluid adhesive or cohesive

A

Both so when the thorax expands and relaxes it pulls the lungs with it

69
Q

State 2 reasons why humans need to absorb large volumes of oxygen from the lungs

A
  • Humans are very large
  • Have a large volume of cells
  • Humans have a high metabolic rate
  • High body temperature
70
Q

List in the correct sequence all the structures that air passes through on its journey from the gas-exchange surface of the lungs to the nose

A

-Alveoli
- Bronchioles
- Bronchus
- Trachea
- Nose

71
Q

Explain how the cells lining the trachea and bronchus protect the alveoli from damage

A

The cells produce mucus that traps particles of dirt and bacteria in the air breathed in. The cilia on these cells move this debris up the trachea and into the stomach. The dirt/ bacteria could damage/ cause infection in the alveoli

72
Q

How does the alveoli provide a short diffusion pathway (3 ways)

A
  • The walls of the capillaries are 1 endothelial, squamous (flattened) cell thick
  • The alveoli wall is 1 epithelial, squamous (flattened) cell thick
  • Therefore the distance between the alveoli and the capillary is really short about 3 micrometers
73
Q

How does the alveoli maintain a concentration gradient

A
  • Blood flows away from the site of gas exchange- taking oxygen with it
  • Deoxygenated blood flows towards the alveolus
  • Inhalation of the air that is rich in oxygen keeps oxygen levels in the alveolus higher than in the capillaries (blood)
74
Q

How does the alveoli provide a large surface area

A
  • There are many alveolus
  • Dense network of capillaries over each alveolus- since there are more places for the oxygen to diffuse into the blood
75
Q

Why is diffusion of gases between the alveoli and the blood very rapid

A
  • RBC are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
  • The distance between the alveolar air and RBC is reduced as the RBC are flattened against the capillary wall
  • The walls of both capillaries and alveoli are both very thin
  • There is a large SA
  • The lungs are constantly being ventilate and the heart is constantly circulating blood around the alveoli
76
Q

What is the walls of the capillaries called and what are they like

A

Endothelial and they are squamous (flattened)

77
Q

What is the walls of the alveoli called and what are they like

A

Epithelial and they are squamous (flattened)

78
Q

Explain how the walls of each alveolus not being more the 0.3 micrometers thick contributes to efficient gas exchange

A

The rate of diffusion is more rapid the shorter the distance across which the gases diffuse

79
Q

Explain how there being 300 million alveoli in each lung contributes to efficient gas exchange

A

There is a very large SA in 600 million alveoli (2 lungs) and this makes diffusion more rapid

80
Q

Explain how each alveolus being covered in a dense network of pulmonary blood capillaries contributes to efficient gas exchange

A

Diffusion is more rapid the greater the concentration gradient. Pumping of blood through capillaries removes oxygen as it diffuses from the alveoli into the blood. The supply of new carbon dioxide as it diffuses out of the blood into the alveoli helps to maintain a concentration gradient that would otherwise disappear as the concentration equalised

81
Q

Explain how each pulmonary capillary being very narrow contributes to efficient gas exchange in the alveoli

A

RBC are flattened against the walls of the capillaries to enable them to pass through. This slows them down, increasing the time for gas exchange and reducing the diffusion pathway, thereby increasing the rate of diffusion

82
Q

If the number of alveoli in each lung was increases to 600 million and the pulmonary ventilation was doubled, calculate how many times greater the rate of diffusion would be

A

4 times greater

83
Q

What is the surfactant

A

A fluid that prevents the alveoli from collapsing or sticking together so they remain open

84
Q

Why do alveoli need to be kept open

A

To increase their surface area

85
Q

What group of people might need artificial surfactant

A

Premature babies since their lungs haven’t fully developed

86
Q

Why do we ventilate (2 reasons)

A
  • To maintain a concentration gradient (by bringing in oxygen rich air)
  • To bring the respiratory medium (air in mammals/ insects and water in fish) in contact with the gas exchange surface
87
Q

In what direction does the respiratory medium always flow

A

Down a pressure gradient

88
Q

What happens when the pressure of the atmosphere is greater than the air pressure inside the lungs

A

Air is forced into the lungs (inhalation)

89
Q

What happens when the air pressure in the lungs is greater than the atmospheric pressure

A

Air is forced out of the lungs (exhalation)

90
Q

When we increase the volume, what happens to the pressure

A

It decrease

91
Q

What 2 types of muscles that can change the pressure within the lungs

A
  • Diaphragm
  • Intercostal muscles (internal and external)
92
Q

What does the contraction of the internal intercostal muscles lead to

A

Exhalation

93
Q

What does the contraction of the external intercostal muscles lead to

A

Inhalation

94
Q

What happens to the intercostal muscles when we inhale

A
  • The internal intercostal muscles relax while the external intercostal muscles contract
95
Q

What happens to the ribs during inhalation

A

They are pulled upwards and outwards, increasing the thoracic volume

96
Q

What happens to the diaphragm during inhalation

A

It contracts, causing it to flatten, which also increases the thoracic volume

97
Q

What does the increases volume in the thorax result in

A

A reduction of the pressure in the lungs, so air is pulled into the lungs

98
Q

Is breathing in (inhalation) active or passive

A

Active

99
Q

Is breathing out (exhalation) active or passive

A

Passive

100
Q

What happens to the intercostal muscles during exhalation

A

The internal intercostal muscles contracts and the external intercostal muscles relax

101
Q

What happens to the ribs during exhalation

A

They move downwards and inwards, decreasing the thoracic volume

102
Q

What happens to the diaphragm during exhalation

A

It relaxes so it pushed up back to a dome shape, so the thoracic volume is further decreased

103
Q

What does decreasing the thoracic volume do to the pressure inside the lungs

A

It increases the pressure, so air is forced out of the lungs

104
Q

What 2 muscles contract during inhalation

A

The diaphragm and the external intercostal muscles

105
Q

During inhalation what 2 things create an increased thoracic volume

A
  • The diaphragm flattens
  • The ribcage moves up and out
106
Q

During inhalation what happens to the pleural membrane to decrease the pleural cavity pressure

A

The outer pleural membrane gets pulled outwards

107
Q

What does the inner pleural membrane pulling outwards do to the surface of the lungs

A

It pulls on the surface of the lungs, causing the alveoli to expand

108
Q

When the surface of the lungs is pulled outwards, the alveoli expands. What happens to the volume and the pressure of the alveoli. So what process is happening (inhalation or exhalation)

A

The volume increases and the pressure decrease the below atmospheric pressure. So we inhale

109
Q

What muscles relax during exhalation

A

The diaphragm and the external intercostal muscles

110
Q

During exhalation, what 2 things decreases the thoracic volume

A
  • The diaphragm returning to its dome shape
  • The ribcage moves downwards and inwards
111
Q

During exhalation, what causes the pressure in the pleural cavity to increase

A

Since there is no pull applied to the outer pleural membrane

112
Q

During exhalation, why is there no pull on the surface of the lungs

A

Since there is no pull on the inner pleural membrane as there is also no pull on the outer pleural membrane

113
Q

What happens to the alveoli when there is no pull on the surface of the lungs

A

They compress

114
Q

What happens to the pressure in the alveoli when it compresses, so what happens to the air

A

It increases to above atmospheric pressure so air is forced out of the lungs

115
Q

During inhalation what happens to the: intercostal muscles, diaphragm, air pressure in the lungs, lung volume, direction in which the air flows

A

The external intercostal muscles contract while the inner intercostal muscles relax. The diaphragm contracts which flattens the dome shape so the volume increases. This increase causes a decrease the in pressure in the lungs. Since the respiratory medium (air) always flows down a pressure gradient, the air flows into the lungs

116
Q

During exhalation, what happens to the: intercostal muscles, diaphragm, air pressure in the lungs, lung volume, and direction in which air moves

A

The external intercostal muscles relax while the inner intercostal muscles contract so the ribs move downwards and inwards. The diaphragm relaxes back into a dome shape which decreases the volume. This decrease in volume increases the pressure within the lungs so it’s above atmospheric pressure. So, air is forced out of the lungs

117
Q

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveol, tidal volume is the volume of air inhaled and exhaled during a single breath when a person is resting

A
  • Less carbon dioxide is exhaled
  • A reduced concentration gradient
  • So more carbon dioxide stays in blood
118
Q

Describe and explain the mechanism that causes lungs to fill with air (3 marks )

A
  • Diaphragm contracts and the external intercostal muscles contract
  • Causes volume increase and pressure decrease
  • Air moves down pressure gradient
119
Q

If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened cells. Explain why death of alveolar epithelium cells reduces gas exchange in human lungs (3 marks)

A
  • Reduced surface area
  • Increased distance for diffusion
  • Reduced RATE of gas exchange
120
Q

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill (3 marks)

A
  • Water and blood flow in opposite directions
  • Maintains concentration gradient of oxygen / blood always passing water with higher oxygen concentration
  • Diffusion along the entire length of the gill plate
121
Q

Describe the gross structure of the human gas exchange system and how we breathe in and out (6 marks)

A
  • Named structure : trachea, bronchi, bronchioles, alveoli
  • Above stucture named in correct order
  • Breathing in : diaphragm and external intercostal muscles contract
  • Causes volume increase and pressure decrease in thoracic cavity
  • Breathing out: Diaphragm relaxes and internal intercostal muscles contract
  • Causes volume decrease and pressure increase in thoracic cavity
122
Q

Explain 3 ways in which an insect’s tracheal system is adapted for efficient gas exchange (3 marks)

A
  • Tracheoles have thin walls so short diffusion distance to cells
  • Large number of tracheoles / highly branched so short diffusion distance to cells
  • Large number of tracheoles/ highly branched so large surface area
  • Fluid in end of tracheoles that moves out during exercise so larger surface area
123
Q

Explain 2 ways in which the structure of fish gills is adapted for efficient gas exchange (2 marks)

A
  • Many filaments and gill plates so large surface area
  • Thin surface so short diffusion pathway

AQA A level Biology (32 decks)

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