UNIT 4 - B 3.1 - Gas Exchange Flashcards
(115 cards)
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
2
Q
What do organisms need to remove in addition to their aerobic needs?
A
remove metabolic waste products such as carbon dioxide
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
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
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
6
Q
When does the surface area-to-volume ration decrease?
A
when the size of the cell increases
7
Q
What is the volume of an organism a reflection of?
A
its metabolic need to exchange respiratory gases
8
Q
What is an organism’s ability to take in and release substances limited by?
A
its outer layer surface area
9
Q
What do organisms with evolved adaptations for gas exchange must have?
A
specialized tissues designed for molecular exchange
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
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
12
Q
Why are gas exhange surfaces thin?
A
to keep diffusion distances short
13
Q
Why are gas exchange surfaces moist?
A
to encourage gas diffusion
14
Q
What does the large surface area of gas exchange surfaces allow?
A
for maximum diffusion
15
Q
What are the respiratory gases?
A
oxygen and carbon dioxide
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
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
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
19
Q
What are body cells continuously doing, utilizing oxygen and producing carbon dioxide?
A
respiring
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
21
Q
What do the numerous dense capillaries within lungs contain?
A
blood that has recently come from respiring body tissues
22
Q
What events must occur in order to maintain concentration gradients for gas exchange?
A
- water must be continuously passed over the gills/air must be continuously refreshed in the lungs
- 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
23
Q
How do lungs expose air to a large surface of gas exchange tissue?
A
by subdividing their volume into alveoli
24
Q
Where are each alveolus located?
A
at a terminal end of one of the branches of tubes that started as the trachea
25
What does it mean to inspire?
breathe in
26
What does it mean to expire?
breathe out
27
What happens within millions of alveoli when we inspire or expire?
most of the air is replaced inside
28
What lines each alveolus?
surfactant
29
What is the surfactant lining each alveolus?
a thin phospholipid and protein film
30
What does the surfactant inside alveoli do?
reduces the surface tension of the moist inner surface and helps prevent each alveolus from collapsing each time air is expired
31
What are bronchioles?
small tubes that connect alveoli and the trachea
32
Why are all of the bronchioles ultimately connected to the trachea?
for access to inspired and expired air
33
What does the spherical shape of alveoli provide?
a vast surface area for the duffusion of oxygen and carbon dioxide
34
What is the diffusion of respiratory gases also helped by?
the dense network of capillaries surrounding the alveoli
35
How do the concentrations of respiratory gases compare in air inspired into the alveoi to the blood in a nearby capillary?
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
36
What do oxygen and carbon dioxide diffuse according to?
their concentration gradient
37
Why to respiratory gases only need to diffuse through two cells to enter or exit the blood stream?
because capillaries are one cell thick and so are each alveolus
38
Why are lungs themselves not capable of purposeful movement?
because the tissues making up the lungs is passive and not muscular
39
What are some of the muscles surrounding our lungs?
the diaphram, muscles of the abdomen, and the external and internal intercostal muscles surrounding the ribs
40
What do all the muscles around the lungs work collectively to do?
either increase or decrease the volume of the thoracic cavity, leading to pressure changes in the lungs
41
What is the mechanism of breathing based on?
the inverse relationship between pressure and volume
42
What does Boyle's law state?
that an increase in volume will lead to a decrease in pressure and vice versa
43
What is the thoracic cavity also called?
the thorax
44
Where are lungs located?
in the thorax
45
What is the thoracic cavity closed to?
outside air
46
What is the only opening in the lungs?
through the trachea (via mouth and nasal passages)
47
What is the diaphram?
a large dome shaped muscle that forms the "floor" of the thoracic cavity
48
What happens when the diaphram contracts?
it flattens the dome shape and increases the volume of the thoracic cavity
49
What are the steps of inspiration?
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
What is a partial vacuum?
the decrease in pressure inside the lungs
51
What leads to deeper breathing and more air moving into the lungs during exercise?
the abdominal muscles and intercostal muscles acheive a greater initial thoracic volume
52
What is a spirometer?
a device that measures lung volume
53
What kind of air volumes can be measured using a spirometer?
tidal volume, inspiratory reserve volume, expiratory reserve volume, vital capacity
54
What is tidal volume?
volume of air breathed in/out during typical cycle when person is at rest
55
What is inspiratory reserve volume?
max volume of air that a person can breathe in
56
What is expiratory reserve volume?
mac volume of air that a person can breathe out
57
What is vital capacity?
the sum of the inspiratory reserve volume, tidal volume and expiratory reserve volume
58
What advantages are there to leaves being thin, only a few cells thick?
the diffusion of gases is quick and efficient, allows for a large surface area-to-volume ratio for efficient diffusion
59
What are the two primary energy-related processes within plants?
cell respiration and photosynthesis
60
What are plant cells producing through aerobic cell respiration?
ATP molecules for energy-requiring reactions
61
Why do plants use photosynthesis when light is available?
to make sugars as fuel for cell respiration
62
What is the summary reaction for cell respiration within plants?
glucose + oxygen = carbon dioxide + water
63
What is the summary reaction for photosynthesis within plants?
carbon dioxide + water = glucose + oxygen
64
How do rates of cellular respiration and photosynthsis compare within plants?
cellular respiration is fairly constant while photosynthesis rate depends heavily on light availability
65
How does the rate of cell respiration compare to the rate of photosynthesis in plants when conditions are optimal for photosynthesis?
the rate of photosynthesis is far greater than the rate of cell respiration
66
What is a waxy cuticle in plants?
a wax lipid layer that covers the surface of leaves and prevents uncontrolled and excessive leaf water loss by evaporation
67
What are upper epidermis in plants?
small cells on the upper surface of leaves that secrete a waxy cuticle
68
What is the palisade mesophyll in plants?
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
What is the spongy mesophyll in plants?
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
What are veins in plants?
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
What do xylem allow water to do?
move up from the root system to the leaves
72
What do phloem allow water and dissolved sugars to be?
distributed to other parts of the plant
73
What is a lower epidermis in plants?
small cells on the lower surface of leaves that secrete waxy cuticle
74
Where are guard cells forming stomata embedded?
in the lower epidermis
75
What are stomata in plants?
numerous microscopic openings on the lower surface of leaves
76
What are each stoma composed of?
two guard cells which can create an opening or close it when needed
77
What happens when a stoma is open?
it permits carbon dioxide to enter the leaf and at the same time water vapour and oxygen to exit the leaf
78
Why does the location of stomata on the lower surface of leaves limits water loss as a result of transpiration?
because the lower surface of leaves experiences lower temperatures compared to the upper surface
79
What is the evaporation of water through open stomata called?
transpiration
80
What is transpiration a natural consequence of?
a leaf's function to accomplish photosynthesis
81
What happens when a leaf opens its stomata?
carbon dioxide enters as a reactant for photosynthesis while excess oxygen diffuses out
82
Why will water also evaporate through any open stomata?
becuase the mesophyll area is very humid
83
Where can water that evaporates through the stomata be traced back to?
water that entered the roots and has reached the upper sections of the plant
84
What can transpiration amount to when conditions are optimal?
a significant amount of water
85
Why does increased light increase the rate of transpiration in plants?
because light stimulates guard cells to open stomata
86
Why does increased temperature increase the rate of transpiration in plants?
becuase it increases molecular movement including increased evaporation of water
87
Why does increased wind speed increase the rate of transpiration in plants?
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
Why does increased humidity lead to a decreased rate of transpiration in plants?
because it lessens the water concentration gradient between the inside and outside of the leaf
89
When would a change in temperature, wind speed and humidity not affect transpiration?
if there is too little light because the stomata would then be closed and the rate of transpiration would be zero
90
What is haemoglobin?
the protein molecule found within red blood cells
91
What are erythrocytes?
red blood cells
92
What is haemoglobin responsible for?
carrying most of the oxygen within the bloodstream
93
What is the basic construct of erythrocytes?
a plasma membrane surrounded by cytoplasm filled with haemoglobin molecules
94
What is the construct of each haemoglobin molecule?
composed of four polypeptides, quaternary structure, each polypeptide has a haem group near its center, each haem group has an iron atom inside
95
What is really binding with oxygen when haemoglobin reversibly binds to an oxygen molecule?
the iron atom within the haem group
96
Why is haemoglobin able to transport 4 oxygen molecules at once?
because haemoglobin has a total of 4 iron atoms within the 4 haem groups
97
When is haemoglobin said to be saturated?
when it is carrying its max 4 oxygen molecules
98
What is cooperative binding?
the phonomenon where there is an increase in affinity/attraction for oxygen when haemoglobin is already bound to an oxygen molecule(s)
99
When does haemoglobin have the greatist affinity for oxygen?
when it alread has 3 oxygen molecules
100
How does oxygen increase haemoglobin's affinity for more oxygen?
it changes the haemoglobin's shape
101
When will haemoglobin not have any affinity for oxygen?
when it alread has all 4 oxygens that it can carry
102
what is allostery?
the binding of carbon dioxide to the polypeptide chain(s) of haemoglobin and the resulting change in haemoglobin's affinity for oxygen
103
Where does carbon dioxide bind to in haemoglobin instead of the iron atoms?
it binds to the polypeptide resgions of the molecule
104
What is the allosteric site of a polypeptide?
the area of each polypeptide where carbon dioxide binds
105
What do the structural differences in foetal haemoglobin allow for?
it to have a higher affinity for oxygen compared to the haemoglobin of the mother
106
Where do capillaries of the mother come very close to the capillaries of the foetus?
in the placenta of the mother
107
What does the mother's and foetus's capillaries being very close allow for?
molecular exchange between the mother and the foetus including oxygen and carbon dioxide
108
What encourages diffusion of the mother's oxygen to the foetus?
the concentration gradient between the blood of the mother and the foetus, aided by the foetal haemoglobin's greater affinity for oxygen
109
What happens when a haemoglobin molecule bonds to a carbon dioxide?
its affinity for oxygen decreases
110
When does haemoglobin have a greater tendancy to give up oxygen molecules?
in the presence of carbon dioxide
111
What is the Bohr shift?
the change in affinity of haemoglobin in the presence of carbon dioxide
112
What is the partial pressure of a gas?
the pressure exerted by a single gas within a mixture of gases
113
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)
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
What would a greater affinity for oxygen look like on a oxygen dissociation curve?
a shift to the left
115
What would increased carbon dioxide mean for oxygen dissociation curves?
it would shift to the right
