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Biology > 3.3.2 gas exchange > Flashcards

3.3.2 gas exchange Flashcards

1
Q

what is a gas exchange surface

A

boundary between outside and inside environment that gas exchange occurs over

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2
Q

what do organisms need to diffuse across gas exchange surfaces as quickly as possible?

A

oxygen and carbon dioxide

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3
Q

what do most gas exchange surfaces have to increase the rate of diffusion?

A

large surface area
thin - often 1 layer of epithelial cells (short diffusion pathway)

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4
Q

what do most organisms often do to help with rate of diffusion in gas exchange?

A

organism maintains steep concentration gradient of gases across the exchange surface, increases rate of diffusion

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5
Q

gas exchange in single celled organism

A

single celled organisms absorb/release gases by diffusion through their cell surface membranes

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6
Q

do single celled organisms have a specialised gas exchange system?

A

large surface area, thin surface, short diffusion pathway so no need for specialised gas exchange system

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7
Q

what is the gas exchange surface in fishes?

A

the gills

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8
Q

do fish have special adaptions to get enough oxygen?

A

there’s a lower concentration of oxygen in water than in air so fish have special adaptations to get enough of it

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9
Q

structure of the gills: how does water enter and leave the fish

A

water, containing oxygen, enters the fish through its mouth and passes out through the gills

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10
Q

structure of the gills: what is each gill made of

A

each gill is made of lots of thin plates (gill filaments)

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11
Q

structure of the gills: what do gill filaments give?

A

gill filaments give a large surface area for exchange of gases so increase rate of diffusion

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12
Q

structure of the gills: what are gill filaments covered in?

A

gill filaments are covered in lots of lamellae which increase surface area even more

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13
Q

structure of the gills: what features do lamellae have?

A

lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion between the water and the blood

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14
Q

the counter current system in fish: what is it?

A

in fishes’ gills blood flows through the lamellae in 1 direction and water flows over them in the opposite direction (counter current system)

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15
Q

the counter current system in fish: what does it do?

A

the cc system means the water with a relatively high oxygen concentration always flows next to blood with a lower concentration of oxygen

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16
Q

the counter current system in fish: what does this do to the concentration gradient?

A

means that steep concentration gradient is maintained between the water rand the blood over the whole length of the gill so as much oxygen as possible diffuses from the water into the blood

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17
Q

gas exchange in dicotyledonous plants:
what do plants need carbon dioxide for?

A

plants need carbon dioxide for photosynthesis which produces O2 as a waste gas

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18
Q

gas exchange in dicotyledonous plants:
what do plants need O2 for?

A

plants need O2 for respiration , which produces CO2 as a waste gas

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19
Q

gas exchange in dicotyledonous plants: what is the main gas exchange surface in the leaves?

A

the main gas exchange surface is the surface of the mesophyll cells in the leaf

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20
Q

gas exchange in dicotyledonous plants:
how are mesophyll cells well adapated to their function?

A

mesophyll cells are well adapted to their function by having a large surface area

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21
Q

gas exchange in dicotyledonous plants:
where would you find the mesophyll cells?

A

the mesophyll cells are inside the leaf

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22
Q

gas exchange in dicotyledonous plants:
how do gases move in and out

A

gases move in and out through pores in the epidermis (mostly the lower epidermis) called stomata

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23
Q

gas exchange in dicotyledonous plants:
what do stomato do

A

the stomata can open to allow exchange of gases, and close if the plant is losing too much water

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24
Q

gas exchange in dicotyledonous plants:
what do guard cells do

A

guard cells control the opening and closing of the stomata

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25
Q

gas exchange in insects:
what do terrestrial insects use for gas exchange

A

terrestrial insects have microscopic air filled pipes (tracheae) which the use for gas exchange

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26
Q

gas exchange in insects (1):
how does air move into the tracheae?

A

air moves into the tracheae through pores on the surface (spiracles).

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27
Q

gas exchange in insects (2):
where does oxygen travel?

A

oxygen travels down the concentration gradient towards the cells.

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28
Q

gas exchange in insects (3):
what do the tracheae branch off into

A

tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells so oxygen diffuses directly into the respiring cells - insect’s circulatory system doesn’t transport O2

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29
Q

gas exchange in insects (4):
what does carbon dioxide do

A

CO2 from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere

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30
Q

gas exchange in insects (5):
what do insects do to move air in/out of the spiracles

A

insects use rhythmic abdominal movements to move air in and out of the spiracles

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31
Q

control of water loss:
what does exchanging gases often result in

A

exchanging gases tends to make you lose water

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32
Q

control of water loss in insects:
spiracles

A

if insects are losing too much water they close their spiracles using muscles

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33
Q

control of water loss in insects:
cuticles/hairs

A

insects have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracles = reduce evaporation

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34
Q

control of water loss in plants:
how are plant’s stomata usually in the day

A

plant’s stomata usually kept open during day to allow gaseous exchange

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35
Q

control of water loss in plants:
guard cells

A

water enters the guard cells so they become turgid = opens stomatal pore. if plant starts to get dehydrated , guard cells lose water and become flaccid which closes the pore

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36
Q

what are xerophytes

A

plants specially adapted for warm/dry/windy environments where water loss is a problem

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37
Q

examples of xerophytic adaptations
sunken stomata

A

stomata sunk in pits to trap water vapour, reducing concentration gradient of water between the leaf and the air, reduces evaporation of water from the leaf

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38
Q

examples of xerophytic adaptations
epidermal hairs

A

layer of ‘hairs’ on the epidermis to trap water vapour around the stomata

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39
Q

examples of xerophytic adaptations
curled leaves

A

curled leaves within the stomata inside, protecting them from the wind - windy conditions increase rate of diffusion/evaporation

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40
Q

examples of xerophytic adaptations
number of stomata

A

a reduced number of stomata = fewer places for water to escape

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41
Q

examples of xerophytic adaptations
cuticles

A

thick waxy, waterproof cuticles on leaves and stems to reduce evaporation

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42
Q

what is the role of the gas exchange system in humans?

A

role of the gas exchange system is to supply your blood with oxygen, and remove CO2 from your body

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43
Q

structure of the human gas exchange system:
step one

A

as you breathe in, air enters the trachea (windpipe).

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44
Q

structure of the human gas exchange system:
step two

A

the trachea splits into 2 bronchi, one bronchus leading to each lung

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45
Q

structure of the human gas exchange system:
step three

A

each bronchus then branches off into smaller tubes called bronchioles

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46
Q

structure of the human gas exchange system:
step four

A

the bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged

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47
Q

structure of the human gas exchange system:
step five

A

the ribcage, intercostal muscles and diaphragm all work together to move air in and out

48
Q

intercostal muscles
where are they found

A

the intercostal muscles are found between the ribs, there are 3 layers of intercostal muscles

49
Q

intercostal muscles
what layers of intercostal muscles do you need to be aware of

A

the internal and external intercostal muscles

50
Q

intercostal muscles
where are the internal intercostal muscles found

A

on the inside of the external intercostal muscles

51
Q

ventilation
what does ventilation consist of

A

ventilation consists of inspiration (breathing in) and expiration (breathing out)

52
Q

ventilation
what is it controlled by

A

it’s controlled by the movements of the diaphragm, internal/external intercostal muscles and ribcage

53
Q

inspiration
step one

A

during inspiration the external intercostal and diaphragm muscles contract

54
Q

inspiration
step two

A

this causes the ribcage to move upwards/outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity (space where lungs are)

55
Q

inspiration
step three

A

as the volume of the thoracic cavity increases, lung pressure decreases to below atmospheric pressure

56
Q

inspiration
step six

A

air will always flow from an area of higher pressure to an area of lower pressure (down a pressure gradient) so air flows down the trachea and into the lungs

57
Q

inspiration
what type of process is it?

A

inspiration is an active process as it requires energy

58
Q

expiration
step one

A

during expiration the external intercostal and diaphragm muscles relax

59
Q

expiration
step two

A

the ribcage moves downwards and inwards , and the diaphragm curves upwards again so it becomes dome shaped

60
Q

expiration
step three

A

volume of the thoracic cavity decreases, causing the air pressure to increase to above atmospheric presssure

61
Q

expiration
step four

A

air is forced down the pressure gradient and out of the lungs

62
Q

expiration
what type of process is it?

A

normal expiration is a passive process as it doesn’t require any energy

63
Q

what other type of expiration is there?

A

forced expiration, e.g. blowing out candles

64
Q

what happens in forced expiration

A

the external intercostal muscles relax and internal intercostal muscles contract, pulling the ribcage further down and in. the movement of the 2 sets of intercostal muscles is antagonistic (opposing)

65
Q

alveoli and gas exchange
where does gas exchange
happen

A

in microscopic air sacs called alveoli found in the lungs in large numbers

66
Q

alveoli and gas exchange
what are the alveoli surrounded by?

A

the alveoli are surrounded by a network of capillaries

67
Q

alveoli structure
walls of alveolus

A

the walls of each alveolus is made from a single layer of thin, flat cells called alveolar epithelium

68
Q

alveoli structure
walls of capillaries

A

walls of the capillaries are made from capillary endothelium

69
Q

alveoli structure
what do the walls of alveoli contain

A

the walls of the alveoli contain the protein elastin which is elastic so helps the alveoli to return to their normal shape after inhaling/exhaling air

70
Q

movement of carbon dioxide and oxygen through the gas exchange system:
where does oxygen move first?

A

air (containing oxygen) moves down the trachea, bronchi and bronchioles into the alveoli (down a pressure gradient)

71
Q

movement of carbon dioxide and oxygen through the gas exchange system:
where does oxygen move second

A

oxygen then moves into the blood where it can be transported round the body (happens down a diffusion gradient)

72
Q

movement of carbon dioxide and oxygen through the gas exchange system:

A

carbon dioxide moves down its own diffusion and pressure gradients, but in the opposite direction to oxygen so it can be breathed out

73
Q

gas exchange in the alveoli:
oxygen

A

oxygen diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium, and into haemoglobin in the blood

74
Q

gas exchange in the alveoli:
carbon dioxide

A

carbon dioxide diffuses into the alveoli from the blood

75
Q

factors affecting the rate of diffusion
how are alveoli adapted?

A

alveoli have features that speed up the rate of diffusion so gases can be exchanged quickly

76
Q

factors affecting the rate of diffusion
how are alveoli’s exchange surface adapted

A

thin exchange surface - alveolar epithelium is one cell thick so there is a shorter diffusion pathway which speeds up diffusion

77
Q

factors affecting the rate of diffusion
how are alveoli’s surface area adapted

A

a large surface area - are millions of alveoli so there is a large surface area for gas exchange

78
Q

factors affecting the rate of diffusion
concentration gradient

A

steep concentration gradient of oxygen and carbon dioxide between the alveoli and the capillaries = increases rate of diffusion

79
Q

factors affecting the rate of diffusion

A

the concentration gradient is constantly maintained by the flow of blood and ventilation

80
Q

what does lung disease affect?

A

ventilation and gas exchange in the lungs

81
Q

what is tidal volume

A

volume of air in each breath

82
Q

what is the tidal volume usually for adults

A

between 0.4 and 0.5 dm^3

83
Q

what is ventilation rate

A

the number of breaths per minute

84
Q

what is the ventilation rate for a healthy person

A

15 breaths

85
Q

what is forced expiratory volume

A

maximum volume of air that can be breathed out in 1 second

86
Q

what is forced vital capacity (FVC)

A

maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in

87
Q

give some examples of lung diseases

A

tuberculosis, fibrosis, asthma, emphysema

88
Q

lung disease example: tuberculosis
what is tuberculosis caused by?

A

pulmonary tuberculosis (TB)
is a lung disease caused by bacteria

89
Q

lung disease example: tuberculosis
what happens when some becomes infected with tuberculosis bacteria?

A

immune system cells build a wall around the bacteria in the lungs which forms small, hard lumps called tubercles

90
Q

lung disease example: tuberculosis
what happens to infected tissue within the tubercles

A

infected tissue within the tubercles dies and the gaseous exchange surface is damaged, so tidal volume is decreased

91
Q

lung disease example: tuberculosis
what additional lung disease can TB also cause

A

TB also causes fibrosis, which reduces the tidal volume further

92
Q

lung disease example: tuberculosis
how does TB affect tidal volume/ventilation rate

A

reduced tidal volume means less air is inhaled with each breath so take in enough oxygen patients have to breathe faster (increased ventilation rate)

93
Q

lung disease example: tuberculosis
symptoms of TB

A

persistent cough, coughing up blood/mucus, chest pains, shortness of breath, fatigue

94
Q

lung disease example: fibrosis
what is fibrosis?

A

fibrosis is the formation of scar tissue in the lungs

95
Q

lung disease example: fibrosis
what can cause fibrosis?

A

can be the result of an infection or exposure to substances e.g. asbestos or dust

96
Q

lung disease example: fibrosis
how and why does fibrosis affect tidal volume and FVC?

A

scar tissue is thicker/less elastic than normal lung tissue = lungs less able to expand/hold less air = tidal volume/FVC reduced

97
Q

lung disease example: fibrosis
how does fibrosis affect rate of gas exchange

A

there is a reduction in the rate of gas exchange, diffusion is slower across a thicker scarred membrane

98
Q

lung disease example: fibrosis
how does fibrosis affect someone’s ventilation rate

A

those with fibrosis have a faster ventilation rate than normal to get enough air into their lungs to oxygenate their blood

99
Q

lung disease example: fibrosis
symptoms of fibrosis

A

shortness of breath, a dry cough, chest pain, fatigue and weakness

100
Q

lung disease example: asthma
what is asthma

A

asthma is a respiratory condition where the airways become inflamed and irritated

101
Q

lung disease example: asthma
what is the cause of asthma?

A

usually because of an allergic reaction to substances e.g. pollen or dust

102
Q

lung disease example: asthma
what happens in an asthma attack, stage 1

A

during an asthma attack, the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced

103
Q

lung disease example: asthma
what happens in an asthma attack, stage 2

A

this causes constriction of the airways, making it difficult to breathe properly

104
Q

lung disease example: asthma
what happens in an asthma attack, stage 3

A

air flow in and out of the lungs is severely reduced, so less oxygen enters the alveoli and moves into the blood

105
Q

lung disease example: asthma
how does an asthma attack affect forced expiratory volume

A

reduced air flow means forced expiratory volume is severely reduced

106
Q

lung disease example: asthma
symptoms

A

wheezing, tight chest, shortness of breath

107
Q

lung disease example: asthma
how do the symptoms come on during an attack

A

during an attack, symptoms come on very suddenly

108
Q

lung disease example: asthma
how are the symptoms treated?

A

they can be relieved by drugs, often inhalers, which cause the muscle in the bronchioles to relax, opening up the airways

109
Q

lung disease example: emphysema
what is emphysema

A

emphysema is a lung disease caused by smoking/long term exposure to air pollution

110
Q

lung disease example: emphysema
how is emphysema caused

A

foreign particles in the smoke/air become trapped in the alveoli, causing inflammation which attracts phagocytes to the area

111
Q

lung disease example: emphysema
what do the phagocytes produce?

A

the phagocytes produce an enzyme that breaks down elastin (protein found in the walls of alveoli)

112
Q

lung disease example: emphysema
what does elastin do

A

elastin is elastic so helps the alveoli return to their normal shape after inhaling/exhaling air

113
Q

lung disease example: emphysema
how does loss of elastin affect the alveoli

A

loss of elastin means the alveoli can’t recoil to expel air as well (it remains trapped in the alveoli)

114
Q

lung disease example: emphysema
how does loss of elastin affect the alveoli walls/rate of gas exchange

A

loss of elastin also leads to destruction of the alveoli walls, reducing the alveoli’s surface area, reducing the rate of gaseous exchange

115
Q

lung disease example: emphysema
symptoms

A

shortness of breath, wheezing

116
Q

lung disease example: emphysema
how does emphysema affect ventilation rate

A

people with emphysema have increased ventilation rate as they try to increase the amount of air (containing oxygen) reaching their lungs

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