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Exchange systems
gas exchange
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Cards (27)
smaller the organism, the
higher
the SA:V ratio
larger the organism, the
lower
the SA:V ratio
single-cellular organisms:
diffusion is
quick
short
diffusion pathway
high
SA:V ratio
could only diffuse by
itself
multiple-cellular organisms:
diffusion
is slow
lower
SA:V ratio
needs
specialised organs
to exchange substances
diffusion alone is
insufficient
some cells to deep into body to interact with enviroment
the
rate substance exchange
is determined by organisms
SA
:
V ratio
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in alveoli and blood in the capillaries around them (5)
many
alveoli
provide a
large surface area
which allows fast diffusion
alveoli have thin walls so short diffusion pathway
capillaries and alveoli maintain a conc gradient
describe the path by which oxygen goes from alveolus to the blood (2)
through
capillary endothelium
, so longer
diffusion
pathway
Describe how ventilation helps maintain differenvce in oxygen conc (2)
bringing in air
increase
conc of
oxygen breathing out
removes air with
lower
conc
Explain how the counter-current principle allows efficient oxygen uptake in the fish gas exchange system (2)
blood
and
water
flow in
opposite
directions
concentration gradient
maintained along
lamella
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill (3)
water
and
blood flow
in
opposite
directions
maintains
concentration gradient
of
oxygen
diffusion
occurs along
lamellae
Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly (2)
stomata
closed
less
carbon dioxide
uptake for less
photosynthesis
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.
tracheoles have
thin walls
so
short diffusion pathway
large number
of tracheoles provide
large surface area
tracheae provides
tubes
full of
air
so
fast diffusion
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange
many lamellae so large surface area
thin surface so short diffusion pathway
Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills (3)
water
and
blood flow
in
opposite
directions
blood always passing water with
high
concentration of oxygen
diffusion
gradient maintained throughout
length
of gill
ventilation:
inspiration
, requires
energy
expiration
inspiration:
external intercoastal muscles
and
diaphragm
contract
volume in
thorax
increases
lung pressure
decreases
below atmospheric
expiration:
external intercoastal muscles
and
diaphragm
relax
volume of
thorax
decreases
air pressure
increases above
atmospheric
Forced expiration:
air
forced out of lungs
external
intercoastal muscles
relax
internal
intercoastal muscles
contract
Lung structure:
A)
larynx
B)
external intercoastal muscles
C)
trachea
D)
bronchus
E)
bronchioles
F)
intercoastal muscles
G)
diaphragm
7
Alveoli:
alveolar walls
= single layer of thin, flat cells (alveolar epithelium)
creating short diffusion pathway
walls of alveoli contain elastin = elastic = allow recoil
millions of alveoli = large SA
pathway for oxygen:
trachea
bronchi
bronchioles
alveoli
alveolar epithelium
capillary endothelium
Factors affecting diffusion:
thin surface =
alveolar epithelium
=
short pathway
large SA = many
alveoli
maintain steep conc gradient =
ventilation
and
circulation
circulation- blood high in
O2
replaced by blood low in
O2
ventilation- breathing replaces air low in
O2
with air high in
O2
lung function:
tidal volume
- volume of air in each breath
ventilation
/
breathing rate
- number of breaths per min
forced expiratory volume
(FEV1) - maximum volume air breathed out in a second
forced vital capacity
(FVC) - maximum volume of air possible to breathe forcefully out of lungs
PVR =
tidal volume
X
breathing rate
Describe and explain one feature of the alveolar epithelium makes the epithelium well adapted for gas exchange (2)
single
layer of
cells
which
shortens diffusion pathway
suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli (3)
more
carbon dioxide in lungs
so
reduced
concentration gradient
so
more
carbon dioxide stays in blood
describe the path by which oxygen goes from alveolus to the blood (2)
through
alveolar epithelium
through the capillary endothelium
describe how ventilation helps maintain difference in oxygen concentration (2)
air
brought in contains higher conc of oxygen
alveolus
removes air with low conc of oxygen
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