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IB Biology > UNIT 4 - B 3.1 - Gas Exchange > Flashcards

UNIT 4 - B 3.1 - Gas Exchange Flashcards

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1
Q

What does it mean for an organism to be aerobic?

A

They require oxygen to metabolize energy from organic substances such as glucose

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2
Q

What do organisms need to remove in addition to their aerobic needs?

A

remove metabolic waste products such as carbon dioxide

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3
Q

How do some organisms, such as single-celled life forms exchange oxygen and carbon dioxide directly with the atmosphere?

A

Through their plasma membranes

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4
Q

Why have larger multicellular organisms evolved complex adaptations involved in gas exchange between the atmosphere or water habitat and other tissues?

A

because of their metabolically active tissues which may lie deep within the organism and far away from their environment

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5
Q

What is the problem of getting gases directly to and from an organism’s interior cells compounded by?

A

the surface area-to-volume ratio

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6
Q

When does the surface area-to-volume ration decrease?

A

when the size of the cell increases

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7
Q

What is the volume of an organism a reflection of?

A

its metabolic need to exchange respiratory gases

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8
Q

What is an organism’s ability to take in and release substances limited by?

A

its outer layer surface area

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9
Q

What do organisms with evolved adaptations for gas exchange must have?

A

specialized tissues designed for molecular exchange

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10
Q

Where are the specialized tissues required for gas exchanged found?

A

in the skin of some small organisms, gills of aquatic organisms, and lungs of some larger terrestrial organisms

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11
Q

What are gas exchange surfaces characterized by?

A

being thin, being moist, having a large surface area, and being permeable to respiratory gases

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12
Q

Why are gas exhange surfaces thin?

A

to keep diffusion distances short

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13
Q

Why are gas exchange surfaces moist?

A

to encourage gas diffusion

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14
Q

What does the large surface area of gas exchange surfaces allow?

A

for maximum diffusion

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15
Q

What are the respiratory gases?

A

oxygen and carbon dioxide

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16
Q

What do the properties of gas exchange surfaces allow for?

A

the max volume of gases to be exchanged across the surface in the shortest amount of time

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17
Q

What must be maintained for oxygen to diffuse into the blood and carbon dioxide to diffuse out of the blood?

A

concentration gradients

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18
Q

What has blood recently been within when it is first circulated to the gills, for example?

A

capillaries of the muscles and other body tissues

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19
Q

What are body cells continuously doing, utilizing oxygen and producing carbon dioxide?

A

respiring

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20
Q

What does the blood that leaves body tissues contain a higher and lower concentration of compared to before the blood reached the active body tissues?

A

higher levels of carbon dioxide and lower levels of oxygen

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21
Q

What do the numerous dense capillaries within lungs contain?

A

blood that has recently come from respiring body tissues

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22
Q

What events must occur in order to maintain concentration gradients for gas exchange?

A
  1. water must be continuously passed over the gills/air must be continuously refreshed in the lungs
  2. there must be a continuous blood flow to thh dense network of blood vessels in both the body tissues and the tissues of the gills/lungs
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23
Q

How do lungs expose air to a large surface of gas exchange tissue?

A

by subdividing their volume into alveoli

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24
Q

Where are each alveolus located?

A

at a terminal end of one of the branches of tubes that started as the trachea

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25
Q

What does it mean to inspire?

A

breathe in

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26
Q

What does it mean to expire?

A

breathe out

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27
Q

What happens within millions of alveoli when we inspire or expire?

A

most of the air is replaced inside

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28
Q

What lines each alveolus?

A

surfactant

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29
Q

What is the surfactant lining each alveolus?

A

a thin phospholipid and protein film

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30
Q

What does the surfactant inside alveoli do?

A

reduces the surface tension of the moist inner surface and helps prevent each alveolus from collapsing each time air is expired

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31
Q

What are bronchioles?

A

small tubes that connect alveoli and the trachea

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32
Q

Why are all of the bronchioles ultimately connected to the trachea?

A

for access to inspired and expired air

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33
Q

What does the spherical shape of alveoli provide?

A

a vast surface area for the duffusion of oxygen and carbon dioxide

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34
Q

What is the diffusion of respiratory gases also helped by?

A

the dense network of capillaries surrounding the alveoli

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35
Q

How do the concentrations of respiratory gases compare in air inspired into the alveoi to the blood in a nearby capillary?

A

air inspired into teh alveoli has a higher concentration of oxygen and a lower concentration of carbon dioxide compared to the blood in a nearby capillary

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36
Q

What do oxygen and carbon dioxide diffuse according to?

A

their concentration gradient

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37
Q

Why to respiratory gases only need to diffuse through two cells to enter or exit the blood stream?

A

because capillaries are one cell thick and so are each alveolus

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38
Q

Why are lungs themselves not capable of purposeful movement?

A

because the tissues making up the lungs is passive and not muscular

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39
Q

What are some of the muscles surrounding our lungs?

A

the diaphram, muscles of the abdomen, and the external and internal intercostal muscles surrounding the ribs

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40
Q

What do all the muscles around the lungs work collectively to do?

A

either increase or decrease the volume of the thoracic cavity, leading to pressure changes in the lungs

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41
Q

What is the mechanism of breathing based on?

A

the inverse relationship between pressure and volume

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42
Q

What does Boyle’s law state?

A

that an increase in volume will lead to a decrease in pressure and vice versa

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43
Q

What is the thoracic cavity also called?

A

the thorax

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44
Q

Where are lungs located?

A

in the thorax

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45
Q

What is the thoracic cavity closed to?

A

outside air

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46
Q

What is the only opening in the lungs?

A

through the trachea (via mouth and nasal passages)

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47
Q

What is the diaphram?

A

a large dome shaped muscle that forms the “floor” of the thoracic cavity

48
Q

What happens when the diaphram contracts?

A

it flattens the dome shape and increases the volume of the thoracic cavity

49
Q

What are the steps of inspiration?

A
  1. the diaphram contracts, increasing the volume of the thoracic cavity
  2. at the same time, the external intercostal muscles and one set of abdominal muscles contracts to help raise the rib cage, also increasing the volume of the thoracic cavity
  3. due to the increase in volume of the thoracic cavity, the pressure inside decreases
  4. The lung tissue responds to the lower pressure by increasing its volume
  5. this leads to a partial vacuum - air comes in through the open mouth/nasal passages to counter the partial vacuum within the lungs and fills the alveoli
50
Q

What is a partial vacuum?

A

the decrease in pressure inside the lungs

51
Q

What leads to deeper breathing and more air moving into the lungs during exercise?

A

the abdominal muscles and intercostal muscles acheive a greater initial thoracic volume

52
Q

What is a spirometer?

A

a device that measures lung volume

53
Q

What kind of air volumes can be measured using a spirometer?

A

tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity

54
Q

What is tidal volume?

A

volume of air breathed in/out during typical cycle when person is at rest

55
Q

What is inspiratory reserve volume?

A

max volume of air that a person can breathe in

56
Q

What is expiratory reserve volume?

A

mac volume of air that a person can breathe out

57
Q

What is vital capacity?

A

the sum of the inspiratory reserve volume, tidal volume and expiratory reserve volume

58
Q

What advantages are there to leaves being thin, only a few cells thick?

A

the diffusion of gases is quick and efficient, allows for a large surface area-to-volume ratio for efficient diffusion

59
Q

What are the two primary energy-related processes within plants?

A

cell respiration and photosynthesis

60
Q

What are plant cells producing through aerobic cell respiration?

A

ATP molecules for energy-requiring reactions

61
Q

Why do plants use photosynthesis when light is available?

A

to make sugars as fuel for cell respiration

62
Q

What is the summary reaction for cell respiration within plants?

A

glucose + oxygen = carbon dioxide + water

63
Q

What is the summary reaction for photosynthesis within plants?

A

carbon dioxide + water = glucose + oxygen

64
Q

How do rates of cellular respiration and photosynthsis compare within plants?

A

cellular respiration is fairly constant while photosynthesis rate depends heavily on light availability

65
Q

How does the rate of cell respiration compare to the rate of photosynthesis in plants when conditions are optimal for photosynthesis?

A

the rate of photosynthesis is far greater than the rate of cell respiration

66
Q

What is a waxy cuticle in plants?

A

a wax lipid layer that covers the surface of leaves and prevents uncontrolled and excessive leaf water loss by evaporation

67
Q

What are upper epidermis in plants?

A

small cells on the upper surface of leaves that secrete a waxy cuticle

68
Q

What is the palisade mesophyll in plants?

A

a densely packed region of cylindrical cells in the upper portion of the leaf which contains numerous chloroplasts and are located to recieve max sunight for photosynthesis

69
Q

What is the spongy mesophyll in plants?

A

loosely packed cells located below the palisade layer and above the stroma which have few chloroplasts and many air spaces, providing a large surface area for gas exchange

70
Q

What are veins in plants?

A

structures that enclose the fluid transport tubes called xylem and phloem, veins are located centrally within a leaf to provide access to all cell layers

71
Q

What do xylem allow water to do?

A

move up from the root system to the leaves

72
Q

What do phloem allow water and dissolved sugars to be?

A

distributed to other parts of the plant

73
Q

What is a lower epidermis in plants?

A

small cells on the lower surface of leaves that secrete waxy cuticle

74
Q

Where are guard cells forming stomata embedded?

A

in the lower epidermis

75
Q

What are stomata in plants?

A

numerous microscopic openings on the lower surface of leaves

76
Q

What are each stoma composed of?

A

two guard cells which can create an opening or close it when needed

77
Q

What happens when a stoma is open?

A

it permits carbon dioxide to enter the leaf and at the same time water vapour and oxygen to exit the leaf

78
Q

Why does the location of stomata on the lower surface of leaves limits water loss as a result of transpiration?

A

because the lower surface of leaves experiences lower temperatures compared to the upper surface

79
Q

What is the evaporation of water through open stomata called?

A

transpiration

80
Q

What is transpiration a natural consequence of?

A

a leaf’s function to accomplish photosynthesis

81
Q

What happens when a leaf opens its stomata?

A

carbon dioxide enters as a reactant for photosynthesis while excess oxygen diffuses out

82
Q

Why will water also evaporate through any open stomata?

A

becuase the mesophyll area is very humid

83
Q

Where can water that evaporates through the stomata be traced back to?

A

water that entered the roots and has reached the upper sections of the plant

84
Q

What can transpiration amount to when conditions are optimal?

A

a significant amount of water

85
Q

Why does increased light increase the rate of transpiration in plants?

A

because light stimulates guard cells to open stomata

86
Q

Why does increased temperature increase the rate of transpiration in plants?

A

becuase it increases molecular movement including increased evaporation of water

87
Q

Why does increased wind speed increase the rate of transpiration in plants?

A

because wind removes water vapour at the entrance of stomata which leads to an increase in the water concentration gradient between the inside and outside of the leaf

88
Q

Why does increased humidity lead to a decreased rate of transpiration in plants?

A

because it lessens the water concentration gradient between the inside and outside of the leaf

89
Q

When would a change in temperature, wind speed and humidity not affect transpiration?

A

if there is too little light because the stomata would then be closed and the rate of transpiration would be zero

90
Q

What is haemoglobin?

A

the protein molecule found within red blood cells

91
Q

What are erythrocytes?

A

red blood cells

92
Q

What is haemoglobin responsible for?

A

carrying most of the oxygen within the bloodstream

93
Q

What is the basic construct of erythrocytes?

A

a plasma membrane surrounded by cytoplasm filled with haemoglobin molecules

94
Q

What is the construct of each haemoglobin molecule?

A

composed of four polypeptides, quaternary structure, each polypeptide has a haem group near its center, each haem group has an iron atom inside

95
Q

What is really binding with oxygen when haemoglobin reversibly binds to an oxygen molecule?

A

the iron atom within the haem group

96
Q

Why is haemoglobin able to transport 4 oxygen molecules at once?

A

because haemoglobin has a total of 4 iron atoms within the 4 haem groups

97
Q

When is haemoglobin said to be saturated?

A

when it is carrying its max 4 oxygen molecules

98
Q

What is cooperative binding?

A

the phonomenon where there is an increase in affinity/attraction for oxygen when haemoglobin is already bound to an oxygen molecule(s)

99
Q

When does haemoglobin have the greatist affinity for oxygen?

A

when it alread has 3 oxygen molecules

100
Q

How does oxygen increase haemoglobin’s affinity for more oxygen?

A

it changes the haemoglobin’s shape

101
Q

When will haemoglobin not have any affinity for oxygen?

A

when it alread has all 4 oxygens that it can carry

102
Q

what is allostery?

A

the binding of carbon dioxide to the polypeptide chain(s) of haemoglobin and the resulting change in haemoglobin’s affinity for oxygen

103
Q

Where does carbon dioxide bind to in haemoglobin instead of the iron atoms?

A

it binds to the polypeptide resgions of the molecule

104
Q

What is the allosteric site of a polypeptide?

A

the area of each polypeptide where carbon dioxide binds

105
Q

What do the structural differences in foetal haemoglobin allow for?

A

it to have a higher affinity for oxygen compared to the haemoglobin of the mother

106
Q

Where do capillaries of the mother come very close to the capillaries of the foetus?

A

in the placenta of the mother

107
Q

What does the mother’s and foetus’s capillaries being very close allow for?

A

molecular exchange between the mother and the foetus including oxygen and carbon dioxide

108
Q

What encourages diffusion of the mother’s oxygen to the foetus?

A

the concentration gradient between the blood of the mother and the foetus, aided by the foetal haemoglobin’s greater affinity for oxygen

109
Q

What happens when a haemoglobin molecule bonds to a carbon dioxide?

A

its affinity for oxygen decreases

110
Q

When does haemoglobin have a greater tendancy to give up oxygen molecules?

A

in the presence of carbon dioxide

111
Q

What is the Bohr shift?

A

the change in affinity of haemoglobin in the presence of carbon dioxide

112
Q

What is the partial pressure of a gas?

A

the pressure exerted by a single gas within a mixture of gases

113
Q

How could you calculate the percentage of oxygen released to tissue using an oxygen dissociation curve? (when y-axis = percentage of haemoglobin saturation and x-axis = partial pressure)

A

by subtracting the left y-axis intersect point (the lower percentage of haemoglobin saturation) from the right y-axis intersect point (the higher percentage of haemoglobin saturation)

114
Q

What would a greater affinity for oxygen look like on a oxygen dissociation curve?

A

a shift to the left

115
Q

What would increased carbon dioxide mean for oxygen dissociation curves?

A

it would shift to the right

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