adaptations for gas exchange Flashcards
(85 cards)
1
Q
define gas exchange
A
process by which oxygen reaches cells and carbon dioxide is removed from them
2
Q
define gas ventilation
A
the process of moving the respiratory medium (air or water) over the respiratory surface to maintain a concentration gradient, replacing stale area high in CO2 with fresh oxygenated air
3
Q
define respiration
A
series of chemical reactions that result in the release of energy in the form of ATP
4
Q
define respiratory pigment
A
a molecule which increases the oxygen-carrying capacity of the blood
5
Q
define trachea
A
a system of branched chitin lined air tubes in insects
6
Q
define “ends of tracheoles”
A
site of gas exchange in insects
7
Q
define spiracles
A
holes in an insect’s exoskeleton which can open and close like valves to allow exchange of gases and reduce water loss
8
Q
define gill lamellae
A
site of gas exchange in fish
9
Q
define alveoli
A
site of gas exchange in mammals
10
Q
define parallel flow
A
gas exchange system where blood in the gill capillaries circulates in the same direction as water flowing over the gills
11
Q
define “counter-currenter flow”
A
gas exchange system where blood in the gill capillaries circulates in the opposite direction to water flowing over the gills
12
Q
define operculum
A
bony structure in bony fish that provides a protective covering the gill
13
Q
what are the two functions of diffusion?
A
- to supply nutrients
- to remove waste
14
Q
what is the relationship between SA:V and size
A
as size increases, SA:V ratio decreases
15
Q
describe amoeba in terms of gas exchange
A
- extremely large SA:V ratio
- gas exchange occurs across whole surface
- permeable membrane allows diffusion of gases
- specialised gas exchange organs are not required
- diffusion is sufficient to meet the oxygen requirements of the organism
16
Q
describe flatworm in terms of gas exchange
A
- these organisms have evolved a flattened shape to overcome the problem of an increase in size
- this increases the SA:V, therefore no cell in the body is far from the surface (short diffusion distance) - so there is no need for specialised gas exchange organs.
- they exchange gases directly with the environment via diffusion ; diffusion across the permeable membrane is sufficient to meet the oxygen requirements of the organism
17
Q
what shape do earthworms develop during gas exchange?
A
a tubular shape
restricted to damp environments
18
Q
what do earthworms secrete and why?
A
they secrete mucus to keep the cells of the body surface moist, which allows gases to dissolve and diffuse
19
Q
describe gas exchange in earthworms
A
- elongated shape provides a large SA:V compared with a compact organism of similar volume
- they exchange gases directly with the environment by diffusion across the moist surface ; blood vessels close to the body surface so gases can diffuse in/out of the blood and then across the cell covering the body surface
20
Q
describe blood in earthworms (in terms of gas exchange)
A
- blood circulates in the vessels, this maintains a concentration gradient for diffusion of oxygen into the cells and carbon dioxide out
- blood contains the respiratory pigment haemoglobin to carry oxygen to body cells
21
Q
what is meant by a terrestrial organism?
A
an organism that lives on land
22
Q
what do all respiratory surfaces need to have to achieve the maximum rate of diffusion?
A
- large surface area
- short diffusion distance
- oxygen and carbon dioxide
- moist - to allow gases to dissolve and diffuse
23
Q
what additional feature increases the efficiency of gas exchange in organisms which possess a circulatory system and respiratory pigment?
A
- extensive blood supply and blood circulates to maintain a diffusion gradient
- respiratory pigment such as haemoglobin increasing the oxygen carrying capacity of blood
24
Q
the spiracles open and open like valves - why is this important?
A
- to allow exchange of gases
- to reduce water loss
25
what is the gas exchange system for insects?
air diffuses into the insect through paired holes called spiracles running along each side of the body
the spiracles lead to a system of branched chitin lined air tubes called trachea
26
why do many insects have air sacs off the trachea?
to aid ventilation of the tracheal system
27
during periods of activity, how is the trachea ventilated?
by the movements of the abdomen
28
why are the gas exchange retained inside the body of all terrestrial organisms?
- reduces water loss
- reduces heat loss
- protection by the diaphragm or exoskeleton in insects
29
what are the advantages of the insect tracheal system?
- oxygen is supplied directly to issues
- no respiratory pigment in needed
- oxygen diffuses faster in air than in blood
- spiracles close to reduce water loss
30
what is the disadvantage of the insect tracheal system?
- limits the size of the organism (diffusion distance would be too large)
- tracheoles are not extensively ventilated and diffusion distance is too big (takes too long for gases to diffuse down the tracheoles)
31
what is the role of chitin in insects?
- surface of tracheoles is lined with a spiral fold of chitin
- keeps airways open during body movements, while allowing some flexibility
32
how does the fluid at the end of the tracheoles help to improve the efficiency of gas exchange?
oxygen dissolves in the fluid and when muscles contract, this fluid (with oxygen) is drawn into muscle cells
33
what problems are caused by living in water?
- water has less oxygen than air
- the rate of diffusion is slower in water
- water is a dense medium and so does not flow as freely as air
34
what two main groups can fish be categorised into and what is this according to?
1. cartilaginous fish
2. bony fish
- according to material which makes up their skeleton and also their gill ventilation mechanisms
35
give an example of cartilaginous fish
shark
36
describe cartilaginous fish
- have a skeleton made entirely of cartilage
- nearly all live in sea water
- just behind the head on each side are 5 gill clefts which open at gill slits
- water is taken into the mouth and is forced through the gill slits when the floor of the mouth is raised
37
what is the gill ventilation mechanism in cartliaginous fish?
gas exchange involves PARALLEL flow - blood in the gill capillaries circulates in the SAME direction as water flowing over the gills
38
give an example of a bony fish
herring
39
describe bony fish
- have an internal skeleton made of bone
- gills are covered with a flap called the OPERCULUM
40
what is the gill ventilation mechanism in bony fish?
gas exchange involved COUNTER-CURRENT flow - blood in the gill capillaries circulates in the OPPOSITE direction as water flowing over the gills
41
distinguish between respiration, ventilation and gas exchange
RESPIRATION - reaction producing ATP
VENTILATION - bringing gases into/out of blood and cells
GAS EXCHANGE - bringing gas exchange medium to/from gas exchange surface
42
give 3 features that a gas exchange surface should have to maximise efficiency
- high SA:V
- thin
- moist
- warm
- concentration gradient maintained
43
describe how your gas exchange surface meets one of these requirements
large SA - many alveoli
thin walls - 1 cell thick
moist - lined with water
concentration gradient - ventilation / good blood supply
44
compare insects ventilation during rest and movement
REST - no ventilation
MOVEMENT - abdominal pumping
45
why are gas exchange organs required inside the body for terrestrial organisms?
- to reduce heat loss and water loss
- allows protection by ribs / exoskeleton
46
give 2 ways insects meet the requirements for an efficient exchange surface
thin - short distance from tip of tracheoles to muscle
large SA:V - many tracheoles
47
explain the ventilation mechanism when the water flows in
mouth - opens
operculum - closed
floor of buccal cavity - lowers
volume - increases
pressure - decreases
directon of water flow - in through the mouth
48
explain the ventilation mechanism when the water flows out
mouth - closes
operculum - open
floor of buccal cavity - rises
volume - decreases
pressure - increases
direction of water flow - over the gills and out of the operculum
49
what part of the fish's head allows a one way current of water?
the buccal cavity
50
explain the structure of the gills in bony fish
- along each gill arch there are many thin filaments
- on the thin filaments there are the gill lamellae
- the gill filaments have a large surface area for gas exchange
- blood circulates through the gill lamellae into the capillaries and carbon dioxide diffuses out into the water
51
describe counter-current flow
- blood always meets water with a higher oxygen concentration
- the gradient for diffusion of oxygen into the blood from the water is maintained over the whole length of the gill lamellae
- oxygen diffuses into blood across whole length of gill lamellae
- counter current flow is more efficient than parallel flow as it results in a higher blood oxygen saturation level
52
describe parallel flow
- water is taken into the mouth and blood flows through the gill capillaries in the same direction as the water
- gas exchange is very efficient at first as there is a very steep concentration gradient
- however, about halfway along the gill lamellae, equilibrium is reached and diffusion of oxygen and carbon dioxide is no longer possible
53
what are the five classes of vertebrates?
- amphibians
- reptiles
- birds
- fish
- mammals
54
describe gas exchange in adult amphibians when inactive and active
INACTIVE - diffusion across their moist surface
ACTIVE (e.g mating) - lungs
55
describe the lung structure of an amphibian
lungs have a simple structure with little folding (giving a small surface area) of the gas exchange tissues
56
what is the gas exchange system in amphibian larvae?
the larvae (tadpoles) live in water and have gills for gas exchange
57
Rings of cartilage support the trachea, bronchi and bronchioles. Suggest a reason for this cartilage
to prevent the airway from collapsing during inspiration/inhalation when the pressure is low
58
what is the name of the airtight compartment of the body that encloses the lungs?
thorax
59
explain what happens during inspiration / inhalation
- intercostal muscles contract
- rib cage moves up and out
- diaphragm contracts and flattens
- pleural membranes go out
- volume of thorax increases
- pressure decreases, so air is pushed by external pressure
60
what is the role of goblet cells?
produce and secrete mucus to trap microorganisms
61
what is the role of cilia?
waft to move the mucus up and out of the trachea
62
what is the effect of emphysema lung tissue?
breaks down alveoli air sac walls and drastically reduces gas exchange surface area
63
what is a surfactant?
what is the role of a surfactant?
a chemical substance which covers the surface of the alveoli.
reduces surface tension and prevents the alveoli from sticking together and collapsing when breathing out.
64
suggest why the cellular demand for oxygen is higher in a mammal compared to a fish of the same size?
- mammal has higher body temperature than the fish
- mammal's metabolic rate is higher
- more energy required for support in mammals whereas fish are bouyant
65
why are alveoli suitable as a gas exchange surface?
- permeable = oxygen and carbon dioxide are able to diffuse
- small and many of them = large surface area
- alveoli, capillary walls are one cell thick = short diffusion distance
- each alveolus has an extensive capillary network, circulation of blood = maintains concentration gradient
- moist surfactant = gases dissolve and diffuse easily
66
what is the function of the intercostal muscles?
when these contract the ribs are pulled up and out, increasing the volume of the thorax
67
what is the function of the bronchiole?
bronchi branch into these smaller tubes
68
what is the function of the larynx?
box shaped structure above trachea, contains vocal cords
69
what is the function of the alveoli?
main site of gas exchange, have a large surface area
70
what is the function of the bronchi?
trachea splits in two of these
71
what is the function of the surfactant?
this prevents the alveoli from sticking together and collapsing, it also reduces surface tension
72
what is the function of the trachea?
tube held open by ring of C-shaped cartilage
73
what is the function of the ribs?
these bones are moved by the intercostal muscles and alter the size of the thorax (chest cavity)
74
what is the function of the diaphragm?
this dome shaped muscle relaxes and contacts altering the volume of the thorax
75
explain the pressure during inspiration
- the diaphragm flattens and the rib cage expands pulling on the outer pleural membrane, which lowers the pressure in the pleural cavity
- the inner pleural membrane pulls on the lungs, which increases the volume of the alveoli
- this decreases the pressure in the alveoli
- the pressure in the alveoli is below atmospheric pressure, so air moves in
76
what is the function of the pleural cavity?
contains pleural fluid which acts as a lubricant to reduce friction between the lungs and inside wall of thorax during ventilation
77
what is the function of the epiglottis?
flap of skin that stops food entering the trachea when swallowing
78
what is the function of the pleural membranes?
acts as a lubricant allowing friction-free movement against the inner wall of the thorax
79
what is the role of a respiratory pigment?
increases the oxygen carrying capacity of the blood
80
how are the leaves adapted for gas exchange?
- the leaf blade is flat and thin = short diffusion distance
- the spongy mesophyll layer allows diffusion and circulation of gases which maintains diffusion gradients
- the stomatal pores open and close to allow gas exchange to occur
- mesophyll have a partially permeable membrane to allow diffusion of gases
81
how are leaves adapted to reduce water loss?
- waxy cuticle on upper surface reduces water loss (by evaporation) / waterproofs the leaf
- stomatal pores in lower epidermis reduce water loss by evaporation
- guard cells can control opening to reduce water loss
82
how are leaves adapted for photosynthesis?
- large surface area to absorb as much light as possible
- leaves can orientate themselves towards the sunlight
- leaves are thin to allow light to penetrate layers
- cuticle and epidermis are transparent to allow light to pass to the mesophyll below
- palisade cells are elongated and densely packed together and contain many chloroplasts
- chloroplast can rotate and move to maximise absorption
- intercellular air spaces allow carbon dioxide to diffuse into the cells
83
STOMATA
- where in the leaf are stomata found?
- what is their role?
- how many guard cells surround each stoma?
- what is unusual about guard cells?
STOMATA
- lower epidermis
- open and close to allow gas exchange and reduce water loss
- 2
- they are the only epidermal cells that contain chloroplasts & they have unevenly thickened cell walls
84
describe the mechanism for stomatal opening
- potassium ions are actively transported from the epidermal cells into the guard cells
- stored starch in the guard cells is converted into malate (soluble) by enzymes in the cytoplasm
- the water potential in the guard cells is lowered (due to presence of solutes) so water enters by osmosis
- the guard cells become turgid and curve apart because the outer cell walls are thinner than the inner cell walls
85
why are stomata usually open during the day and closed at night?
OPEN DURING THE DAY to allow carbon dioxide to diffuse into the leaf for photosynthesis
CLOSED AT NIGHT to reduce the loss of water
