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Gas and Solute
Life processes need gases or dissolved Structure of Leaves; Allows diffusion in +
substances to occur. These gases/fluids
move by diffusion, osmosis and active
out of cells.
-Carbon Dioxide diffuses into leaf, into cells.
-Underside of leaf = EXCHANGE SURFACE,
E.g. For photosynthesis, need CO2 and Water covered in stomata, therefore allows CO2 to
For respiration, need glucose and oxygen. diffuse through.
Waste substances need to be removed from -O2, H2O diffuse out from stomata, water also
cells. lost from leaf surface.
-Life processes- gases/fluids need to move -Stomata controlled by guard cells, close
stomata if water loss is too great.
through an EXCHANGE SURFACE, which
-Flattened shape of leaf, increase S.A. Of
have to allow enough of substance through. exchange surface
-Walls of cell inside leaf, form exchange
FOUR factors of adaptation of exchange surface.
surfaces: -Has air spaces, increase area of surface, CO2
-Thin ­ short diffusion pathway more likely to get in.
Water, evaporates from cells in leaf, escapes
-Large Surface area- Maximise diffusion by diffusion, as high cocen in leaf than air.
-Efficient blood supply- lots of vessels
-Gas exchange surfaces-Well ventilated.
NOTE: exchanging substances gets harder, as
the organism gets more complex, as further to
travel.…read more

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The Breathing
The THORAX, is the upper body, above the Ventilation is:
abdomen. System
diaphragm. Below the diaphragm is the
Breathing in:
-Intercostal muscles and diaphragm contract.
-Thorax Vol. Increases.
LUNGS are protected by the ribcage. -Decreases pressure, drawing air in.
Air goes
(Diaphragm flattens, muscles between ribcage
through pull sternum up+out, increases vol.)
And Breathing Out:
-Intercostal muscles and diaphragm relax.
-Thorax Vol. Decreases.
-Increases pressure, air forced out.
(Diaphragm moves up, sternum and ribcage
drop in and down.)
takes Artificial Ventilators help people breathe.
place. Old Days- put a giant case from neck to abdomen-
pumped air out, pressure dropped, lungs expanded-
air drawn in. Air pumped in- opposite effect. Could
interfere with blood flow of lower body.
Modern: ventilators pump air into lungs, then stop
etc. However can burst alveoli.…read more

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Diffusion through cell membranes
Gas Exchange happens in the lungs Inside the Small Intestine
-Job of the lungs: transfer O2 to blood and Millions of Villi; increase surface area
remove CO2. massively.
-Contain millions of alveoli, where gas -Digested food absorbed a lot more
exchange takes place. quickly into blood.
-Have single layer of surface cells.
-Very good blood supply- assist
Alveoli: specialised to maximise
-Enormous S.A.
-Moist lining, for dissolving gases.
-Very thin walls.
-Good blood supplies.…read more

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Water Flow through Plants
Plants Have two types of vessels, the Xylem
and the Phloem.
Xylem: Phloem:
-Made of dead cells -Made of columns of living cells
-No walls between them w/ small hole in ends ­ flow.
-Hole down the middle -Transport food substances,
-Carry water and minerals dissolved sugars from leaves to
from roots to stem & growing regions & storage
-Both directions.
(in the transpiration
stream) Transpiration; loss of water from plants
-Transpiration cause by evaporation & diffusion
of water from leaves.
-Creates shortage of water in leaves, more
water drawn up to replace.
-Means more water drawn up from roots,
therefore constant stream of water through
-Transpiration; side effect of way leaves are
adapted: have to have stomata, for gas
exchange + as higher concentration of water in
plant than outside air.…read more

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Active Transport
When substances are absorbed against a
concentration gradient to an area of
higher concentration from an area of
lower concentration, it requires energy.
Root Hair Cells: Active Transport, stops us from
-Specialised for absorbing water & minerals starving.
-Cells on roots grow into long thin hairs, stick -Used in the body when there is a low
out in soil concentration of nutrients in the gut, but
-Increases surface area for absorption of high concentration in blood.
mineral ions + water -Usually higher concentration of amino
-Most water & mineral ions: absorbed my root acids in gut, therefore diffuse naturally
hair cells. into blood.
-Sometimes lower concentration in gut
TAKE IN MINERALS USING ACTIVE than blood, therefore concentration
TRANSPORT gradient the wrong way.
-concentration of minerals higher in roots than -Active transport allows nutrients to be
soil, therefore diffusion doesn't work, therefore take in from the gut despite the
uses active transport. concentration gradient, but it requires
-Allows plant to absorb minerals from a very ENERGY.
dilute solution.
-Requires ENERGY as against a concentration
gradient.…read more

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