2.2 Adaptations For Gas Exchange Flashcards
1
Q
What is gas exchange
A
The process where gases move passively by diffusion across a surface. Essential gases are transported into cells and waste products carried away
2
Q
What are the gases transported into cells essential for
A
Essential for process like respiration and photosynthesis
3
Q
What is the respiratory surface
A
The body surface where gaseous exchange by diffusion happens over
4
Q
What are the characteristics of respiratory surfaces needed to maintain the maximum rate of diffusion
A
- thin (so diffusion pathway is short)
- permeable to the gases
- moist (so gases can dissolve)
- large surface area to volume ratio (so rate of gas exchange is sufficient to satisfy the organism’s needs)
- mechanism with steep concentration gradient
5
Q
Why is it bad that larger organisms’ cells are a bigger distance away from the respiratory surface
A
Gases can’t reach or be carried away from these cells quickly enough by simple diffusion alone
6
Q
What kind of organisms have a large surface area to volume ratio
A
Tiny organisms like the single celled amoeba.
7
Q
Why is it good to have a large surface area to volume ratio
A
So gases can diffuse quickly enough throughout the organism
8
Q
What kind of organisms have a smaller surface area to volume ratio
A
Huge organisms like elephants and whales.
9
Q
Why and with what are large organisms adapted with to help gas exchanhe
A
Must be adapted with specialised respiratory surfaces, circulatory systems, and blood pigments to facilitate the transport of gases around their bodies
10
Q
Why have large multi cellular organisms evolved specialised respiratory surfaces for gas exchange
A
- metabolic needs are proportional to volume, so larger organisms need more oxygen.
- the external surface of larger organisms is insufficient for gas exchanges.
- diffusion of respiratory gases is proportional to surface area, so in larger organisms the surface area to volume ratio is too small to achieve gas exchange since diffusion distances are too large.
- not enough oxygen can diffuse to all the cells in time to supply their metabolic needs
11
Q
How do small unicellular organisms exchange gases
A
They exchange gases across the cell surface. Their surface are to volume ratio is large enough to supply their needs. Distances within the cel are small so diffusion is rapid enough.
12
Q
Gas exchange in amoeba
A
- unicellular
- large surface area to volume ratio.
- no specialised surfaces
- aquatic so water loss from surface isn’t a problem.
- uses its general body surface for gas exchange. Gets oxygen dissolved from surrounding water through its plasma membrane in simple diffusion
13
Q
Gas exchange in flatworm
A
- multicellular
- large surface area to volume ratio due to flattened shape
- no specialised surfaces for gas exchange
- aquatic so no water loss from surface
- gas exchange occurs by passive diffusion through body wall/surface
14
Q
Gas exchange in earthworm
A
- multicellular
- large surface area to volume ratio due to cylindrical shape
- a simple circulatory system. Blood pigments transport gases throughout body.
- terrestrial, so water loss from surface is a problem.
- gas exchange happens through moist skin and capillaries. As fresh air is taken in through the skin, oxygen drawn into worm’s circulatory system
15
Q
Why are bony fish’s oxygen needs greater than other organisms
A
larger and more active
16
Q
What are bony fish’s specialised gas exchanges surface
A
the gills
17
Q
Explain gills as a specialised gas exchange surface
A
Gills have large surface area due to gill filaments (a specialised respiratory area).
Water forced over gill filaments
18
Q
Why must water be forced over the gill filaments
A
Because water is a dense medium with relatively low oxygen content
19
Q
How is water forced over the gills
A
by a ventilating mechanism
20
Q
What prevents the gills from collapsing to maintain the large surface area
A
The density of water
21
Q
Flow of water is…
A
One way / unidirectional
22
Q
Direction of water in bony fish
A
Water in through mouth and out through gills
23
Q
What does the system of ventilation in a bony fish allow
A
allows water to be passed continuously across the gills even when the fish is resting
24
Q
How is ventilation achieved
A
By pressure changes in buccal (mouth) and opercular (gill) cavities
25
When buccal/mouth is open, what is the operculum/gill
Closed
26
Stage 1 of ventilation process
Mouth opens, floor if buccal cavity lowered.
Volume of buccal cavity increases and pressure decreases.
The operculum remains closed.
Water is pulled into buccal cavity from outside due to change in pressure
27
Stage 2 of ventilation process
Mouth closes and buccal cavity contracts, raising the floor of the buccal cavity.
Water forced across the gills
28
Stage 3 of ventilation process
Pressure in gill cavity increases and forces operculum open.
Water leaves via the operculum
29
What does an extensive network of capillaries in gills allow?
Allow efficient diffusion of oxygen
30
What does the blood pigment haemoglobin and circulatory system do in fish
Carry oxygen throughout the fish
31
What do gill filaments have
Gill plates or lanellae
32
Where does water flow in gill capillaries
Water flows between gill plates (lamellae) in opposite direction to blood flow
33
What does counter current flow do (positive)
Increases efficiency of diffusion by maintaining a steep concentration gradient across the whole gill filament.
Blood always meets water with a relatively high oxygen content
34
Water flows in what direction with blood
Water flows in opposite direction than blood
35
How to identify oxygen vs blood on a graph of counter current flow
Water always contains more oxygen so always higher on graph
36
Why do cartilaginous fish like sharks have a more inefficient system
Parallel flow - Water and blood flow in same direction across gill plate.
37
What is a parallel flow
Water and blood flow in same direction across gill plate
38
Why is parallel flow less efficient than counter current flows
Steep concentration gradient isn’t maintained and rate of diffusion isn’t optimum across entire gill plate. Good in beginning but oxygen in both blood and water will eventually be at equilibrium so there’s no net movement.
39
Why can’t sharks stop swimming
To prevent suffocation. Because of inefficient nature of their ventilation system. Need movement for water to get in, to receive oxygen from it
40
Compare Counter current flow and parallel flow
- CCF water flows across filament in opposite direction to blood flow in gill capillaries. PF water flows across filament in same direction as blood flow in gill capillaries.
- CCF steep concentration gradient is maintained. PF oxygen concentration gradient isn’t maintained and equilibrium is reached
- CCF diffusion of oxygen from water to blood occurs across entire gill plate. Doesn’t in PF
- CCF rate of diffusion high. Lower in PF as equilibrium is reached
- CCF greater amount of oxygen absorbed into blood. Higher oxygen saturation percentage. PF less oxygen absorbed into blood. Lower percentage oxygen saturation of blood
41
Characteristics of respiratory surface in amphibians, reptiles and birds
- large surface area
- moist surface
- short diffusion pathway
- circulatory system with blood pigments
- internal lungs
- ventilation mechanism
42
Positives of large surface area in respiratory surface
For rapid diffusion of respiratory gases
43
Positives of moist surface in respiratory surface
To facilitate rapid diffusion of gases
44
Positives of short diffusion patheay in respiratory surface
Thin walls so easier to diffuse through
45
Positives of circulatory system with blood pigments in respiratory surface
To carry oxygen. E.g haemoglobin
46
Positives of internal lungs in respiratory surface
Minimise loss of water and heat
47
Positives of ventilation mechanism in respiratory surface
Forces respiratory medium (air) to and from respiratory surface. To ensure oxygen is brought to and carbon oxide is removed from the gas exchange surface
48
How do inactive amphibians do gas exchange
Use their moist skin
49
How do active amphibians do gas exchange
Use simple lungs.
Frog lungs pair of hollow sacs with highly folded surface to increase surface area.
50
How do tadpoles do gas exchange
Uses gills
51
Why can’t reptilian skin be used as a respiratory surface
Impermeable to gases
52
Why are reptile lungs more efficient than amphibians
Reptilian lungs sac-like and have more complex folding than amphibian lungs. Reptiles have ribs as well
53
How is ventilation aided in reptiles
Aided by movement of ribs by the intercostal muscles
54
What does ventilation mean
Actively moving the respiratory medium across the respiratory surface
55
What is the respiratory surface
Where gases are exhanged
56
Why is efficient gas exchange essential in birds
They’re warm blooded and have a high respiration rate
57
Structure of bird lungs
Small, compact, composed of numerous branching air tubes called bronchi
58
What do the smallest air tubes (parabronchi) have?
Have an extensive blood capillary network where gas exchange takes place
59
How does structure of parabronchi help gas exchange
Parabronchi end in large, thin walled air sacs which help in ventilation.
No diaphragm but do have ribs and flight muscles for efficient ventilation
60
What can cause dehydration in terrestrial organisms
Water evaporates from the body surface
61
What does efficient gas exchange require
A thin, permeable surface with a large surface area
62
What have insects evolved to reduce water loss
Evolved a rigid waterproof exoskeleton, which is covered by a cuticle
63
Why can't insects use their body surface to exchange gases by diffusion?
Have a relatively small surface area to volume ratio
64
What system of gas exchange have insects evolved, different to other land animals
The tracheal system
65
In the tracheal system of insects, where does gas exchange occur
Through spiracles (paired hole running along side of body)
66
Structure of tracheal system
Paired holes called spiracles run along side of the insect's body. Spiracles lead into a system of branched, chitin lined air-tubes called tracheae
67
What is tracheae
A system of branched, chitin lined air tubes
68
What do spiracles do?
Can open and close like valves to allow gas exchange to take place and reduces water loss
69
What do resting insects rely on
Rely on diffusion to take in oxygen and remove carbon dioxide
70
What happens to insects during periods of activity (e.g flight)
Movements of the abdomen ventilate the tracheae
71
What are the ends of the tracheae called?
Tracheoles
72
What are tracheoles
A gas exchange surface
73
What is NOT needed to transport the oxygen in tracheal system
A respiratory pigment like haemoglobin, and a circulatory system isn't needed to transport oxygen
74
Why aren't respiratory pigments like haemoglobin and a circulatory system needed to transport oxygen in a tracheal system?
Tracheoles are in direct contact with the cells and tissues so oxygen is passed DIRECTLY to the cells. It's very rapid
75
How structure of muscle fibres connected to tracheoles help gas exchange
Never exceed 20um in diameter which provides short diffusion path for gas exchange. So, diffusion is rapid enough to supply sufficient oxygen to the cells and tissues
76
What happens to tracheoles during insect flight and how does this help gas exchange
Fluid levels in the tracheoles decrease during flight to provide more surface area for gas exchange and also further shortens diffusion pathway
77
What ventilates the tracheal system in insects
Compression and expansion of the abdomen
78
What does ventilation do
Ventilation carries the respiratory medium (air) to the respiratory surface at the end of the tracheoles
79
What do spiracles do
Open and close to allow air in and out of tracheal system
80
Order of spiracles opening
Thorax spiracles open first, just before the abdominal spiracles. Both open for the same length.
81
Spiracles closed for a long period of time to...
Prevent water loss
82
Abdomen shape relationship to spiracles
Thorax spiracles open as the abdomen expands, abdomen is compressed before abdomen spiracles open.
83
What does the compression and expansion of the abdomen do?
Act as a pump to draw air in via the thorax spiracles, through the system and forces it out via the abdominal spiracles
84
What is the thorax
An airtight compartment where the lungs are enclosed within
85
Function of epiglottis
Valve which prevents food getting into trachea
86
Function of trachea
Carries air to bronchi
87
Function of cartilage rings
Helps support trachea while still allowing it to move and flex during breathing
88
Function of bronchi
Carries air to bronchioles
89
Function of bronchioles
Carries air to alveoli
90
Function of alveoli
Respiratory surface where gas exchange occurs
91
Function of diaphragm
Separates thorax and abdomen and helps ventilate lungs
92
Function of ribs
Protect lungs and ventilation
93
Function of intercostal muscles
Move the ribs
94
Function of pleural membranes
Secrete fluid into the space between them which prevents damage to lungs due to friction
95
Ventilation in humans meaning
Ventilation is a mechanism which moves the respiratory medium (air) to and from the respiratory surface (the alveoli)
96
How do mammals ventilate their lungs
By negative pressure breathing, forcing air down into the lungs
97
How do intercostal muscles carry out inspiration and expiration
- inspiration : contract
- expiration : relax
98
How do ribs carry out inspiration and expiration
Inspiration : move up and out
Expiration : moves back down and in
99
How does diaphragm carry out inspiration and expiration
Inspiration : contracts and flattens
Expiration : relaxes and domes
100
How does volume of thorax carry out inspiration and expiration
Inspiration : increases
Expiration : decreases
101
How doors pressure of thorax carry out inspiration and expiration
Inspiration : decreases
Expiration : increases
102
How does outside air pressure carry out inspiration and expiration
Inspiration: greater than the pressure in the thorax; air is forced into lungs.
Expiration : pressure inside lungs greater than outside; air is forced out of lungs
103
If diaphragm is flat and ribcage has moved up and out, is it inspiration or expiration
Inspiration. We can tell thorax is contracting
104
What surrounds each lung and lines the thorax
Pleural membranes
105
What does the cavity between membranes contain
Pleural fluid
106
What does pleural fluid do
When breathing, this fluid acts as a lubricant, allowing friction free movement against wall of thorax
107
What is the gas exchange surface in mammals
The alveoli
108
Characteristics of alveoli to help with gas exchange
- large surface area to volume ratio.
- moist surface for gases to dissolve.
- thin walls for short diffusion pathway
109
Structure of surface of alveoli
One cell thick and composed of squamous epithelium tissue.
110
Each alveolus is covered by an…
Extensive capillary network
111
What maintains a steep concentration gradient for diffusion in the alveoli
Oxygenated blood is carried away from the alveolus and blood rich in carbon dioxide returns
112
What is a surfactant
Anti sticking chemical
113
What do surfactants do
Cover surface of each alveolus, which prevents alveoli collapsing when breathing out (by reducing surface tension)
114
Who are surfactants often given to
Premature babies to prevent the alveoli in their immature lungs sticking together
115
Composition of air in lungs - OXYGEN
% of oxygen in alveolus lower than in inspired air.
% of oxygen in expired air lower than in inspired air
Inspired air : 20
Alveolar air : 14
Expired air : 16
116
Composition of air in the lungs - CARBON DIOXIDE
% of carbon dioxide in the alveolus is higher than in inspired air.
% of carbon dioxide is in expired air is higher than in inspired air.
Inspired air : 0.4
Alveolar air : 6
Expired air : 4
117
Composition of air in lungs - NITROGEN
% of nitrogen in the alveolus is similar than in inspired air.
% of nitrogen is in expired air is similar than in inspired air (Not much taken in)
Inspired air : 79
Alveolar air : 80
Expired air : 79
118
Composition of air in lungs - WATER VAPOUR
Inspired air: variable
Alveolar air : saturated
Expired air : saturated
119
Why is the percentage oxygen in the alveolus lower than in inspired air
Because it mixes with air already in the lungs, which had lower percentage oxygen content
120
Why does inspired air have more % of oxygen than expired air
Oxygen is absorbed into the red blood cells at the alveoli and used in aerobic respiration.
121
Why does expired air have more % of carbon dioxide than inspired air
Carbon dioxide produced by respiration diffuses from the blood plasma into the alveoli
122
Why does inspired air have the same % of nitrogen than expired air
Nitrogen isn’t absorbed or used so all that is inhaled gets exhaled
123
Why does inspired air have more variable water vapour, whereas expired air has more saturated water vapour
The water content of the atmosphere varies. Alveoli are permanently lined with moisture; water evaporates from them and is exhaled
124
How to calculate % of oxygen extracted
% oxygen absorbed / % air that is oxygen
X 100
125
Why do plants need to exchange gases
For respiration and photosynthesis
126
What is the main gas exchange surface in plants
The leaf
127
What happens to plants during the day
They respire and photosynthesise
128
What happens to plants during the night
Photosynthesis stops but respiration continues
129
During the day, most if the carbon dioxide plants need for photosynthesis…
Diffuses into the leaf from the air. And some is provided by respiration
130
In plants, most of the oxygen produced by photosynthesis…
Diffuses out of the leaves
131
At night, the oxygen needed for respiration… (in plants)
Diffuses into the leaf from the atmosphere
132
How does the structure of a leaf relate to its function
The leaf blade (lamina) is thin and flat, with a large surface area.
Diffusion pathways for gases are short
133
Function of waxy cuticle
Prevents water loss. Transparent to let light in
134
Function of upper epidermis
Transparent and thin to allow light to penetrate through leaf
135
Function of palisade mesophyll
Packed with chloroplasts for photosynthesis
136
Function of spongy mesophyll
The gaps allows for the circulation of gases. Contains chloroplasts for photosynthesis
137
Function of air spaces
Allows carbon dioxide to diffuse into the cells and oxygen out (during the day for photosynthesis)
138
Function of guard cells
Open and close the stomata
139
Function of stomatal pores
For gas exchange
140
Function of lower epidermis
Thin and contains waxy cuticle
141
Function of vascular bundles (xylem and phloem)
Provides the leaf with water and minerals
142
Adaptations of the leaf for gas exchange
- spongy mesophyll tissue : many air spaces for circulation of gases.
- stomatal pores : allow gases to exchange between outside air and leaf
143
Steps of CO2 gas exchange in leaf
- carbon dioxide diffuses through stomata down a concentration gradient.
- carbon dioxide then circulated the intercellular spaces between mesophyll cells, by diffusion
- carbon dioxide dissolves in the moist layer, which covers each cell, and diffuses into the mesophyll cells, across the cell membrane
144
Adaptations of leaf for photosynthesis
- large surface area
- can orientate themselves
- thin
- cuticle and epidermis are transparent
- palisade mesophyll cells
- chloroplasts can rotate and move within the mesophyll cells
145
How does large surface area in leaf help photosynthesis
captures as much light as possible
146
How does leaves' ability to orientate help photosynthesis
So they're held at perpendicular angle to the sun, to expose the surface to as much light as possible.
147
How does thinness of leaves help photosynthesis
To allow light to penetrate to lower cell layers.
148
How does a transparent cuticle and epidermis help with photosynthesis in leaves
to allow light to penetrate to the mesophyll.
149
How do palisade mesophyll layers help with photosynthesis
are elongated and densely arranged in layers to allow more chloroplasts
150
How do chloroplasts being able to rotate and move help with photosynthesis in leaves
Allows them to arrange themselves in the best possible position for light absorption.
151
How do intercellular spaces and spongy mesophyll help with photosynthesis in leaves
Allow gases to circulate. CO2 diffuses into the cells and oxygen diffuses out the cells
152
What are stomata
Pores which allow the exchange of gases. Water is lost through stomata
153
Each stomata is bounded by...
2 guard cells
154
Structure of guards cells
- Have thick inner wall and thin outer wall.. Thick inner wall causes cell to become a curves sausage shape when it swells: opens stomatal pore
- Have chloroplasts.
155
What do guard cells do
Can change shape to open and close the stomata: this controls gas exchange and water loss
156
What happens to plants if they lose too much water
They wilt/cells become flaccid
157
Why do most stomata close at night
To prevent the plant needlessly losing water when the light intensity is too low for photosynthesis
158
If light strikes the upper leaf surface, why are stomata found on lower leaf surface
To reduce water loss
159
Why do guard cells change shape
Due to a change in turgor:
160
What happens when water ENTERS the guard cells
When water ENTERS the guard cells by osmosis, the guard cells swell/become turgid. This opens the stomatal pore since the thicker inner wall causes the guard cell to curve.
161
What happens when water LEAVES the guard cells
When water LEAVES the guard cells by osmosis they become flaccid which closes the stomatal pore
162
Stomata opening mechanism
- during the day (if light intensity is sufficient) potassium ions (K+) are pumped by active transport into the guard cells.
- as a result, stored starch is converted to malate.
- this lowers the water potential (becomes more negative)
- water enters cell by osmosis.
- guard cells become turgid and curve apart because their outer walls are thinner than their inner walls.
- this opens the stomatal pore, allowing gas exchange
163
Stomata closing mechanism
- when light intensity is too low for photosynthesis, potassium ions diffuse down a concentration gradient out the guard cells.
- Malate is converted back into starch by condensation reaction.
- The water potential of the guard cells increases (becomes less negative).
- water leaves the guard cells by osmosis.
- guard cells become flaccid which closes the stomatal pore.
- this prevents gas exchange and reduces water loss
164
Magnification calculation
Size of image / actual size
