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AS Biology - Module 3 > 3.1 Exchange Surfaces > Flashcards

3.1 Exchange Surfaces Flashcards

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1
Q

Generally, how do unicellular organisms get substances from their environment and get rid of waste?

A
  • Through cell membrane (or outer surfaces)

- Have a large SA:VOL ratio + lower demands for nutrients, oxygen etc as less volume

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2
Q

Generally, how to multicellular organisms get substances from their environment and get rid of waste?

A
  • Have specialised systems for exchange to occur
  • Larger so cannot get substances from their outer surfaces; greater distance to diffuse across + this would be too large + slow for an exchange to occur across
  • Larger organisms habve more demand for oxygen and nutrients as they are more active
  • So large organisms need specialised exchange surfaces as well as transport systems
  • Larger have a smaller SA:VOL ratio
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3
Q

What kind of animals have the largest surface area to volume ratio?

A

The smaller the organism, the greater the SA:VOL ratio

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4
Q

Define exchange surface

A

A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other

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5
Q

What is the equation to work out SA:VOL ratio?

A

surface area (cm2) / volume (cm3)

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6
Q

How does SA:VOL ratio affect the rate of diffusion?

A

The smaller the SA:VOL ratio the slower the rate of diffusion

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7
Q

Define gaseous exchange.

A

The movement of gases by diffusion between an organism and its environment across a barrier eg. alveoli

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8
Q

How are the lungs adapted for efficient gaseous exchange?

A
  • Large surface area (alveoli)
  • Thin barrier to minimise diffusion distance (1 cell thick alveoli)
  • Permeable to exchange molecules
  • Good capillary network to maintain concentration gradient
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9
Q

How thick is the barrier between the alveoli and the c apillaries in the lungs?

A

2 cells thick (one from alveoli and one from the capillary)

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10
Q

How is a concentration gradient maintained between the alveoli and the capillaries?

A
  • Constant supply of blood means oxygen removes as soon as it diffuses into the blood to keep the concentration in the blood low compared to the alveoli to keep a steep concentration gradient
  • Reverse for CO2, high in blood and low in alveoli as it is breathed out
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11
Q

What is a surfactant and what is its function in the alveoli?

A
  • Water film lining the alveoli
  • Breath out: evaporates and leaves the lungs
  • Cohesion between water molecules would cause alveoli to collapse
  • Compound (surfactant) produced in alveoli lines them
  • Reduces surface tension + cohesion + stops alveoli collapsing
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12
Q

How does inspiration occur?

A
  • Diaphragm contracts, flattens and moves downwards
  • External intercostal muscles contract + move the ribs up + out
  • Increases the volume inside the thorax + lungs
  • Reduces pressure inside thorax/lungs below atmospheric pressure
  • Air moves into the lungs down a pressure gradient
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13
Q

How does expiration occur?

A
  • Diaphragm relaxes + moves outwards
  • External intercostal muscles relax + move ribs in + down
  • The internal intercostal muscles can contract to help push air out more forcefully
  • Decreases volume inside thorax + lungs
  • Induces the pressure inside thorax/lungs above atmospheric pressure
  • Air moves out of the lungs down a pressure gradient
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14
Q

What features of the alveoli make it ideal for gas exchange?

A
  • Plasma membrane permeable to oxygen and carbon dioxide
  • Large surface area through the infoldings
  • Wall of the alveoli is one cell thick
  • Good blood supply
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15
Q

What are the features of the mammalian gas exchange system that improve efficiency of gaseous exchange?

A
  • Many alveoli
  • The epithelium of the alveoli is very thin
  • There are capillaries running over the surface of the alveoli
  • The lungs are surrounded by the diaphragm and intercostal muscles
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16
Q

How does the many alveoli in the mammalian gas exchange system improve the efficiency of gas exchange?

A

Increases the surface area across which oxygen and carbon dioxide can diffuse

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17
Q

How does the thinness of the epithelium of the alveoli in the mammalian gas exchange system improve the efficiency of gaseous exchange?

A

Decreases the diffusion distance so increases the rate of diffusion

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18
Q

How does the capillaries running over the surface of the alveoli in the mammalian gas exchange system improve the efficiency of gaseous exchange?

A

Gives a good blood supply to maintain the concentration gradient by taking away oxygen and delviering carbon dioxide

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19
Q

How does the lungs being surrounded by the diaphragm and intercostal muscles in the mammalian gas exchange system improve the efficiency of gaseous exchange?

A

Allows ventilation as the diaphragm by contracting and relaxing to adjust the volume in the thorax to adjust the pressure: low pressure and contracting during inspiration and vice versa so that air goes down a pressure gradient

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20
Q

Define tissue.

A

A group of similar cells working together to perform a particular function

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21
Q

What are the tissues in the alveoli?

A
  • Squamous epithelium

- Elastic fibres

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22
Q

What is the squamous epithelium?

A

It is the walls of the alveoli that are one cell thick to provide a short diffusion distance for gaseous exchange

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23
Q

What is the role of the cartilage in the respiratory system?

A
  • Keeps airways open and prevent collapse during inspiration when there’s a low pressure in the thorax
  • Allows some flexibility to move neck without constricting airways
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24
Q

What is the role of the smooth muscle in the respiratory system?

A
  • Contracts to constrict airways

- Reduces flow of air

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25
Q

Why might the smooth muscles reduce the flow of air?

A

To reduce harmful substances going into the lungs, relates to asthma

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26
Q

What is the role of the elastic fibres in the respiratory system?

A
  • They do not contract or relax
  • Stretch when the smooth muscle contracts
  • Recoil when the smooth muscle relaxes to help dilate the airway again
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27
Q

What is the role of the goblet cells in the respiratory system?

A

Secrete mucus to trap bacteria and other partciles to be removed from the lungs to reduce infection

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28
Q

What is the role of the ciliated epithelium in the respiratory system?

A

Waft to and fro to remove mucus from airways up to throat

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29
Q

What is the role of the blood vessels in the respiratory system?

A

Supply lung tissues like the smooth muscle with oxygen for aerobic respiration

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30
Q

What lung tissues are there in the trachea?

A

Cartilage (C-shaped), ciliated epithelium, goblet cells, smooth muscle and elastic fibres

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31
Q

What lung tissues are there in the bronchi?

A

Cartilage (not C-shaped), ciliated epithelium, goblet cells, smooth muscle and elastic fibres

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32
Q

What lung tissues are there in the bronchioles?

A

Ciliated epithelium, smooth muscle, elastic fibres and goblet cells (only in the larger ones)

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33
Q

What lung tissues are there in the alveoli?

A

Elastic fibres

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34
Q

How does a spirometer work?

A
  • During inspiration: take in oxygen from chamber so it goes down
  • During expiration: air pushes into the chamber so it goes up
  • Movements are recorded on the trace (graph) by a data logger
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35
Q

Why do we have a residual volume?

A
  • Lungs can’t be completely compressed
  • Trachea and bronchi held open by cartilage
  • Bronchioles and alveoli held open by elastic fibres
  • Residual volume stops respiratory system from collapsing as they can’t have a vacuum there
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36
Q

How do you work out the tidal volume from a spirometer trace?

A
  • Patient breathes normally

- Measure height of wave (tidal volume) of at least 3 waves and calculate a mean

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37
Q

When using a spirometer, why does the patient have to wear a nose plug?

A

To make sure they only take air from the chamber and not from the environment so you can accurately measure the volume inspired/expired

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38
Q

How do you work out the breaths per minute from a spirometer trace?

A
  • Count the number of breaths taken in a set period of time
  • Divide the number of breaths by this time (in seconds)
  • Multiply by 60 to find the number of breaths per minute
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39
Q

During spriometry, why will the total volume of gas in the spirometer decrease?

A
  • Soda lime absorbs the carbon dioxide breathed out
  • Tells you how much carbon dioxide is breathed out showing how much oxygen is taken in for aerobic respiration
  • The volume of carbon dioxide removed=volume of oxygen used by person. Measures the rate of oxygen intake
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40
Q

Using a spirometer trace, how do you measure the rate of oxygen intake?

A
  • Calculate the difference in volume between 2 peaks/troughs on the trace (in dm3)
  • This gives you the volume of oxygen used
  • Measure the time taken to use this volume of oxygen
  • Divide the volume by the time to give the rate
  • If time is in seconds, to give rate in dm3min-1 you need to divide by the number of seconds then multiply by 60
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41
Q

What are the three main factors that affect the need for an exchange system?

A
  • Size
  • Surface area to volume ratio
  • Level of activity
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42
Q

How does gaseous exchange occur in small organisms?

A
  • Happens over the surface of the body

- Don’t need a specialised exchange system

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43
Q

What exchanges happen in organisms and why?

A
  • Supply of oxygen and nutrients

- Remove waste products so they don’t build up and become toxic

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44
Q

How do larger organisms more than 2 layers of cells) exchange substances?

A

Through specialise exchange systems

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45
Q

Why do larger organisms need specialised exchange surfaces but smaller organisms do not?

A
  • Small: cytoplasm close to the environment. Diffusion gives them enough oxygen to keep cells alive/active
  • Multicellular: several layers of cells Any oxygen/nutrients diffusing from outside have a longer diffusion pathway. Too slow to give innermost cells sufficient supply
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46
Q

What is the surface area to volume ratio like in smaller organisms?

A
  • Small surface area
  • Small volume
  • Large surface area to volume ratio (surface relatively large compared with volume)
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47
Q

What is the surface area to volume ratio like in larger organisms?

A
  • Large surface area
  • Large volume
  • Small surface area to volume ratio (surface relatively small compared with volume)
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48
Q

What size organisms have the largest surface area to volume ratio?

A

Smaller organisms

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49
Q

How do some organisms increase their surface area?

A

Adoptiong different shapes e.g. flatworm (thin, flat body)

50
Q

Why do larger organisms have a smaller surface area to volume ratio?

A

As they get thicker, the volume increases as does the surface area, just not by as much

51
Q

How does level of activity affect the demand for oxygen and nutrients?

A
  • Increases the metabolic activity of the cells
  • Metabolic activity uses energy from food + requires oxygen to release energy from aerobic respiration
  • Cells of active organisms need good supply of nutirents/oxygen to supply energy from movement
  • Need for energy is increased to keep themselves warm ie in mammals
52
Q

What are the features of a good exchange surface?

A
  • Large surface area
  • Thin, permeable barrier
  • Good blood supply
53
Q

How does a large surface area help to make a good exchange surface?

A
  • More space for molecules to pass through them

- Often through folding walls + membranes involved e.g. root hair cell

54
Q

How does a thin, permeable barrier help to make a good exchange surface?

A
  • Reduces diffusion distance

- Shown in alveoli in lungs

55
Q

How does a good blood supply help to make a good exchange surface?

A
  • Brings fresh supply of molecules to one side to keep concentration high
  • Or removes molecules from demand side to keep concentration low
  • Maintains a steep concentration gradient so diffusion can occur rapidly
  • e.g. gills in fish
56
Q

What is the gaseous exchange system in mammals?

A

Lungs and associated airways that carry air into and out of lungs

57
Q

What are the lungs?

A

A pair of inflatable sacs lying in the chest cavity

58
Q

How does air get from the nose to the lungs?

A

Along the trachea (windpipe), then bronchi, then bronchioles, then the alveoli (these are the surfaces where exchange of gases takes place)

59
Q

What are the alveoli?

A

Tiny air filled sacs in the lungs

60
Q

What are the lungs protected by?

A

The ribcage

61
Q

What are the ribs held together by?

A

The intercostal muscles

62
Q

How do gases get exchanged between the alveoli and the blood capillaries?

A
  • By diffusion through thin walls of alveoli
  • Oxygen passes from air in alveoli to blood capillaries
  • Carbon dioxide passes from blood to air in alveoli
  • Lungs maintain steep concentration gradient so diffusion continues
63
Q

How does the large surface area help with gas exchange in the lungs?

A
  • Individual alveoli are very small but there are lots so have a large surface area
  • Total surface area in lungs is about 70m2
  • Alveoli lined with thin layer of moisture, evaporating + is lost as we breathe out
  • Lungs produce surfactant to coat the internal surface of alveoli to reduce cohesive forces between water molevules as these tend to make the alveoli collapse
64
Q

How does the barrier being permeable to oxygen and carbon dioxide help with gas exchange in the lungs?

A
  • Barrier is just wall of alveolus and wall of capillary (2 cells thick)
  • Cells and their plasma (cell surface) membranes readily allow diffusion of oxygen and carbon dioxide as molecules are small and non-polar
65
Q

How does the thin barrier to decrease diffusion distance help with gas exchange in the lungs?

A
  • Alveolus wall one cell thick
  • Capillary wall one cell thick
  • Both walls consist of squamous cells (flattened or very thin)
  • Capillaries are in close contact with alveolus walls
  • Capillaries are so narrow that RBCs are squeezed against capillary wall, closer to air in alveoli to reduce their rate of flow
  • Toyal barried to diffusion is 2 flattened cells, less than 1μm
66
Q

What does squamous mean?

A

Flattened or very thin

67
Q

How does a good supply of blood help with gas exchange in the lungs?

A
  • Maintains a steep concentration gradient so gases continue diffusing
  • Blood system tranpsorts carbon dioxide from tissues to lungs so conc is higher than air of alveoli so it can diffuse into the alveoli
  • Blood system transports oxygen away from lungs so conc is lower than air of alveoli so oxygen diffuses into blood
68
Q

What features of the lungs make it good for gas exchange?

A
  • Large surface area so more space for molecules to pass through
  • Barrier permeable to oxygen and carbon dioxide
  • Thin barrier to decrease diffusion distance
  • Good blood supply to maintain concentration gradient
69
Q

How are the lungs ventilated?

A

By breathing movements, replacing used air in lungs to bring in more oxygen and remove carbon dioxide

70
Q

How does ventilation affect the concentration of oxygen and carbon dioxide in the blood and alveoli?

A
  • Ensures concentration of oxygen in air of alveolus is higher than that in the blood
  • Ensures concentration of carbon dioxide in alveoli is lower than in the blood
71
Q

How does inspiration occur?

A
  • Diaphragm contracts to move down + become flatter (displacing digestive organs downwards)
  • External intercostal muscles contract to raise ribs
  • Volume of chest cavity is increased
  • Pressure in chest cavity drops below the atmospheric pressure
  • Air is moved into the lungs down a pressure gradient
72
Q

How does expiration occur?

A
  • Diaphragm relaxes + pushed up by displaced organs underneath
  • External intercostal muscles relax + ribs fall. Internal intercostal muscles can contract to help push air out more forcefully (usually only during exercise, coughing or sneezing)
  • Volume of the chest cavity decreases
  • Pressure in lungs increases above pressure in surrounding atmosphere
  • Air is moved out of the lungs down a pressure gradient
73
Q

What do the elastic fibres in the walls of the alveolus do?

A

Stretch during inspiration and recoil to dilate airways to push air out during expiration

74
Q

What features must there be of the trachea, bronchi and bronchioles in order for them to be effective?

A
  • Large enough to allow sufficient air to flow without obstruction
  • Supported to prevent collapse when air pressure inside is low during inspiration
  • Flexible to allow movement
75
Q

What are the aiways lined with?

A

Ciliated epithelium

76
Q

Which, the trachea or the bronchus, are narrower?

A

The bronchi are narrower

77
Q

What is the benefit of the cartilage being C-shaped in the trachea?

A

Allows flexibility and space for the food to pass down the oesophagus

78
Q

What airways does cartilage support?

A

Trachea and the bronchi

79
Q

What is the wall of the bronchioles mostly comprised of?

A

Smooth muscle and elastic fibres

80
Q

What do the smallest bronchioles end in?

A

Clusters of alveoli

81
Q

What does the smooth muscle do?

A
  • Contracts
  • Contricts the airways
  • Constriction of lumen restricts flow of air to and from the alveoli
  • Helps when there’s harmful substances in the air
  • Contraction of smooth mucle is involuntary and may be because of an allergic reaction
  • Cannot reverse the effect of contracting on its own
82
Q

What do the elastic fibres do?

A
  • Smooth muscle elongated by elastic fibres
  • When smooth muscle relaxes, deforms elastic fibres
  • As muscle relaxes, elastic fibres recoil to original shape+ size to dilate airway
83
Q

What does a spirometer measure?

A
  • Lung volume

- Measures movement in and out of lungs as person breathes

84
Q

How does a spirometer work?

A
  • Consists of a chamber of air/medical grade oxygen floating on a tank of water
  • Inspiration: air drawn from chamber so lid moves down
  • Expiration: air returns to chamber, raising the lid
  • Movements may be recorded on a data logger
  • Carbon dioxide rich air exhaled is passed through a chamber of soda lime, absorbing the carbon dioxide so oxygen consumption can be measured
85
Q

Why does the air exhaled in spirometry go passed and therefore get absorbed by the soda lime?

A

So that the change of volume measured in the chamber is from the oxygen only, and not from the carbon dioxide exhaled

86
Q

Why can’t spirometry be done for too long at a time?

A

Oxygen concentration in the chamber will become too low that it does not go into the body

87
Q

What precautions must be taken when using a spirometer?

A
  • Subject should be healthy and free from asthma
  • Soda lime should be fresh and functioning
  • Should be no air leaks in the apparatus as this would give invalid/inaccurate results
  • Mouthpiece should be sterilised
  • Water chamber must not be overfilled (or water may enter the air tubes)
88
Q

What 2 things does lung capacity consist of?

A

Vital capacity (which can be measured) and residual volume (which can’t be measured)

89
Q

What is the vital capacity?

A

The maximum volume of air that can be moved by the lungs in one breath

90
Q

How is the vital capacity measured using a spirometer?

A

Taking a deep breath and expiring all the air possible from the lungs

91
Q

What factors affect the vital capacity of a person?

A
  • Size of person
  • Age and gender
  • Level of regular exercise
92
Q

What is the vital capacity of a person generally in the region of?

A

2.5-5.0dm3

93
Q

What might cause the vital capacity of a person to increase?

A

Being a trained athlete

94
Q

What is the residual volume?

A

Volume of air that remains in the lungs even after forced expiration. Air remains in the airways and alveoli

95
Q

What is the general residual volume?

A

1.5dm3

96
Q

What is the tidal volume?

A

The volume of air moved in and out with each breath, normally measured at rest

97
Q

What is the typical tidal volume of a person?

A

0.5dm3 - usually sufficient to supply all the oxygen required by the body at rest

98
Q

What does breathing do?

A

Supplies oxygen for aerobic respiration and removes carbon dioxide produced in respiration

99
Q

How is the oxygen uptake measured using a spirometer?

A
  • As person breathes through spirometer, oxygen is absorbed by blood and replaced by carbon dioxide
  • Carbon dioxide is absorbed by the soda lime in spirometer so volume of air in chamber decreases
  • Decrease can be observed and measured in spirometer trace
  • Can assume volume of carbon dioxide released/absorbed by soda lime equals volume of oxygen absorbed by blood
  • Measuring gradient of decrease in volume enables us to calculate rate of oxygen uptake
100
Q

How do you measure oxygen uptake from a spirometer trace?

A
  • Draw line down to horizontal from two points (both peaks/troughs). Measure the length of time between these points.
  • Measure difference in volume between 2 points
  • Divide by time take for this decrease (unit in dm3s-1 - multiply by 60 for dm3min-1)
101
Q

How can breathing rate be measured from a spirometer?

A

Count the number of peaks in each minute

102
Q

What is the usual breathing rate of a person?

A

12-14 breaths per minute

103
Q

Why might someone have a higher oxygen uptake?

A

Increased demand, e.g. during exercise when muscles are respiring (aerobically) more

104
Q

What will result in an increased oxygen uptake?

A
  • Increased beathing rate

- Deeper breaths

105
Q

How do bony fish get oxygen?

A

From the water they live in, using gills to absorb oxygen dissolved in the water + release carbon dioxide into the water

106
Q

Is the concentration of oxygen higher in the air or in water?

A

The air

107
Q

How many pairs of gills to mnost bony fish have?

A

5

108
Q

What is the bony plate that covers the gills in bony fish called?

A

Operculum

109
Q

What does each gill consist of?

A

2 rows of gill filaments (primary lamellae)

110
Q

What is the structure of the gill filaments?

A
  • Very thin
  • Surface folded into many secondary lamellae (gill plates)
  • Provides a large surface blood
  • Lamellae covered in capillaries
111
Q

What do the capillaries around the gill lamellae do?

A

Carry deoxygenated blood close to the surface of secondary lamellae where exchange takes place

112
Q

How and why do bony fish use a countercurrent flow?

A
  • Blood flows along gill arch + out along filaments to secondary lamellae
  • Blood flows through capillaries in opposite direction to flow of water over lamellae
  • Arrangement causes a countercurrent flow to absorb the maximum amount of water
113
Q

What is the journey of the water from entering the fish to leaving it?

A
  • Mouth opens (operculum is closed)
  • The buccal cavity floor is lowered
  • This increased volume + decreases pressure in buccal cavity compared to outside
  • Water moves into mouth down a pressure gradient
  • Opercular cavity expands (lowering pressure)
  • Buccal cavity floor is raised (increasing pressure)
  • Pressure in buccal cavity is higher than opercular cavity
  • Water moves from buccal cavity over gills to opercular cavity
  • Mouth is now closed + operculum opens
  • Sides of opercular cavity move inwards, increasing pressure
  • Water rushes out of fish through operculum
114
Q

What is the name of the system that bony fish use to keep water flowing over the gills?

A

Buccal-opercular pump

115
Q

Why do insects have an open circulatory system?

A

Circulation is slow and can be affected by body movements

116
Q

What is the journey of the air through an insect?

A
  • Enters through a pore in each segment: spiracle
  • Air transported into body through a series of tubes called tracheae
  • Tracheae divide into smaller tubes calle tracheoles
  • Ends of tracheoles are open + filled with tracheal fluid
  • Gas exchange occurs between tracheole and tracheal fluid
  • Some exchange also occurs across thing walls of tracheoles
117
Q

What kind of circulatory system do insects have?

A

An open circulatory system

118
Q

What is the system of getting air around in an insect called?

A

Tracheal system (air filled, supplies air directly to all respiring tissues)

119
Q

What happens when an insect is active and has a higher demand for oxygen?

A
  • Tracheal fluid can be withdrawn into body fluid
  • Increases surface area of the tracheole wall exposed to air
  • Means more oxygen can be absorbed when insect is active
120
Q

How do many insects ventilate their circulatory system using flexible walls?

A
  • Many have sections of tracheal system expanded with flexible walls
  • These act as air sacs which can be squeezed by action of flight muscles
  • Repetitive expansion + contraction of these sacs ventilate the tracheal system
121
Q

How do some insects use their wings to ventilate their circulatory system?

A
  • Some use movements of wings to alter volume of thorax
  • As thorax volume decreases, air in tracheal system put under pressure + pushed out of tracheal system
  • When thorax increases in volume, pressure inside drops + air is pushed into tracheal system from outside
122
Q

How do locusts ventilate their tracheal system?

A
  • Can alter volume of abdomen by specialised breathing movements
  • Coordinated with opening + closing valves in spiracles
  • As abdomen expands, spiracles at front end of body open + air enters tracheal system
  • As abdomen reduces in volume, spiracles at rear of body open + air can leave the tracheal system

AS Biology - Module 3 (4 decks)

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