B3 AQA Further Biology

Notes on Exchange of Substances.

Covers Active Trasport, Diffusion, Osmosis, Human exchanges (breathing, diffusion of oxygen into the blood stream, diffusion of food into the blood stream) and Plant exchanges (transpiration, osmosis of water and minerals into plant roots and active trasport of nitrate ions into plant roots) 

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  • Created by: Aparna
  • Created on: 17-12-12 10:52
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Further Biology: B3
Exchanges
Type of exchange Type of Molecules Concentration Energy
Gradient
Diffusion Small, dissolved (O2, CO2) Down (high to low) Kinetic
Osmosis Mainly water, solvent Down (high to low) Kinetic
Active Transport small (e.g. glucose), ions Up (low to high) ATP (from
respiration)
Diffusion
DIFFUSION IS THE RANDOM MOVEMENT OF SOLUTE PARTICLES/DISSOLVED SUBSTANCES FROM AN AREA OF HIGH CONCENTRATION TO
AN AREA OF LOW CONCENTRATION.
To speed up diffusion:
Decrease the distance Increase the concentration gradient
Increase the surface area Good blood supply
Good ventilation (in gaseous exchanges)
Osmosis
OSMOSIS IS THE RANDOM MOVEMENT OF SOLVENT MOLECULES (USUALLY WATER) ACROSS A PARTIALLY PERMEABLE MEMBRANE
FROM A REGION OF HIGH CONCENTRATION TO A REGION OF LOW CONCENTRATION
Partially permeable membrane is a thin membrane containing tiny pores that allows small
molecules to pass (e.g. water) but not bigger ones (e.g. ions and sugar molecules).
Molecules move about randomly but the net (overall) movement of particles is along the
concentration gradient.
Depending on the concentration of the solution that surrounds a cell (tissue fluid, which is provided
by the blood capillaries), water will move into or out of the cell through osmosis.

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Active Transport
THE TRANSPORTATION OF MOLECULES FROM A LOW CONCENTRATION TO A HIGH CONCENTRATION (AGAINST THE CONCENTRATION
GRADIENT) USING ATP (ENERGY FROM RESPIRATION)
Energy is required as carrier
proteins pick up specific
molecules and take them
through the cell membrane.
Therefore, cells using active
transport have lots of
mitochondria as that's
where respiration happens.
If respiration stops, active
transport stops.…read more

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It's important for the body parts to be highly
specialised as the size and complexity of an
organism increases the difficulty of exchanging
materials.
Sports Drinks
If the water and ions lost are not replaced, the
ion/water balance of the body is disturbed.
Sweating releases more water than ions so the
balance is disrupted as there is a higher ion
concentration in the blood.
This causes cells in the body to not work as
efficiently.…read more

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All drinks help to rehydrate the body (replace lost water)
Soft drinks contain water, sugar, ions and flavourings but concentrations can vary greatly.
Sport drinks contain sugar to replace the glucose lost during exercise and water and ions.…read more

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Ventilators
Devices that help patients breathe who cannot automatically do so due to disease or injury.
Negative-Pressure Ventilators
E.g. the iron lung, developed for use during epidemics of poliomyelitis as breathing muscles stopped
functioning, was a large tank enclosing the whole patient's body except the head and neck. A pump removes
the air from the tank, creating a vacuum. This causes the patient's thorax to expand and therefore, inhale. The
vacuum is them released, the thorax and lungs recoil, and the patient exhales.…read more

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