Movement of Substances
The taking in of heat, fluids, gases or nutrients (small molecules) by a
cell, through its membrane. In digestion, the taking in, by the blood
and lymph systems (lacteals), of the end products of digestion
(monosaccharides, amino acids, fatty acids, glycerol, etc.).
Usually precedes a process. These processes require energy in the
form of ATP, which is released from glucose in the mitochondrion
during the process of respiration. Oxygen is usually required.
The taking in of mineral ions from the soil by the roots of plants. This
requires energy in the form of ATP. The presence of oxygen in the
soil is also required for respiration by the root cells to produce the
necessary ATP.
The movement of substances (solutes or ions) from a region of low
concentration (hypotonic) to a region of higher concentration
(hypertonic) against the concentration gradient through a semipermeable membrane (cell membrane). It requires the use of energy
(in the form of ATP) by the cell. ATP is a product of respiration.
Respiration usually requires oxygen and occurs in the mitochondria.
All cells in the body are bathed in this fluid called. It is similar to
blood plasma but without the plasma proteins. Substances in the
blood diffuse from capillaries into the fluid and then into the cells.
Cellular waste products diffuse in the reverse direction.
absorption
active
active absorption
active transport
body fluid / extracellular fluid /
tissue fluid
Force with which molecules of the same substance stick to each
other.
cohesion /
cohesive
Most acceptable theory of water movement through a plant. Based
on cohesive forces of water, i.e. the force of attraction between
water molecules is great enough to maintain a continuous column of
water.
cohesion-tension
hypothesis /
Dixon-Joly theory
The amount or number of molecules of a solvent, which is dissolved
in a solute.
concentration
The difference in the concentration/number of molecules between
two different areas. The greater the difference, the faster the rate of
movement of molecules will be, e.g. diffusion, active transport, etc.
The production of notched edges on red blood corpuscles by
drawing water from them by osmosis. Achieved by placing red blood
cells in a solution that is hypertonic to the cell cytoplasm.
concentration
gradient
crenation
The losing of water by a cell(s) or molecules.
dehydration
The opposite of plasmolysis. The cell membrane moves towards the
cell wall as a result of water being drawn into the cell by osmosis.
The cell gradually becomes turgid. Achieved by placing a plant cell in
a solution that is hypotonic to the cell sap.
deplasmolysis
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The movement of solute from a region of high solute concentration
to a region of lower solute concentration. No permeable or semipermeable membrane is necessary for this process to occur. No
diffusion
energy used by the cell in this process, i.e. it is passive. Examples
are: gaseous exchange in alveoli; absorption through villi of small
intestine.
The bursting of red blood corpuscles with the release of
haemoglobin. Achieved by placing red blood corpuscles in a solution, haemolysis
which is hypotonic to the cell sap.
A solution with a higher solute concentration than the surrounding
solution.
hypertonic
A solution with a lower solute concentration than the surrounding
solution.
hypotonic
Cannot be penetrated by particles of solids or liquids.
impermeable
A solution with the same solute concentration as another solution.
isotonic
A special case of diffusion. It is the movement of solvent (always
water) from a region of high solvent concentration to a region of
lower solvent concentration through a semi-permeable membrane,
until both concentrations are equal. No energy used by the cell for
osmosis
osmosis to take place, i.e. it is a passive process. Examples are: water
entering root hair cell; water moving from cell to cell in
transpiration.
The entry of water into a cell by osmosis exerts an outward pressure.
osmotic pressure
The pressure necessary to prevent osmosis is ...
Not requiring the use of energy, e.g. diffusion and osmosis, or
brought about by outside forces.
passive
The movement of particles from an area of high concentration to an
area of lower concentration. No energy is required for the process.
(passive) diffusion
Movement of substances across the cell membrane which does not
involve the use of energy by the cell, e.g. diffusion and osmosis.
passive transport
Refers to a membrane; allows molecules or ions of a certain
maximum size to pass through. The cell wall allows all molecules
and ions to pass through irrespective of size.
The shrinking of the plasma membrane (cell membrane) away from
the cell wall with the loss of turgidity as a result of water being
drawn out of the cell by osmosis. This does not normally occur in
nature but is achieved by placing a plant cell in a solution, which is
hypertonic to the cell sap. A cell will become flaccid before
becoming plasmolysed.
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(fully) permeable
plasmolysis
Refers to the cell membrane. Allows certain molecules or ions to
pass through but prevents others.
semi- / selectively
/ partially
permeable
e.g. cell membrane, visking tubing. Certain molecules or ions can
pass through but others cannot, depending on size.
semi-permeable
membrane
Substance that is dissolved in a liquid.
solute
A mixture of a solute and a solvent. Solute is the substance that will
be dissolved and solvent is the liquid that will do the dissolving,
usually water.
solution
A liquid in which the solute is dissolved.
solvent
Inflated by pressure from within as a result of water been drawn
into the cell by osmosis. Achieved by placing a plant cell in a solution
that is hypotonic to the cell sap. Water flows in and is collected in
the vacuoles and the cells swell and push out against the cell walls.
turgid
State of a plant cell due to pressure built up in the cell; exerted
outwards and caused by the cell taking in water by osmosis.
turgor pressure
Pressure exerted inwards by the cell wall in response to turgor
pressure. This prevents a plant cell from bursting.
wall pressure
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