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Transport Across Cell Membranes - This process DOES NOT require ATP Complete Plasmolysis occurs when the cell
ENERGY from respiration. becomes Flaccid.
Methods of Transport: Incipient Plasmolysis is when the cell membrane
There are several methods of transport: Channel Proteins: is just beginning to move away from the cell wall.
- Facilitated Diffusion.
- These help with the diffusion of charged Turgor:
particles such as ions.
- Osmosis. When water potential is zero and no more water van
- Endocytosis / Exocytosis. - Channel proteins have pores lined with enter the cell.
- Active Transport. polar groups.
- This makes the channel hydrophilic so Endocytosis and Exocytosis:
Diffusion: that water-soluble molecules may travel Substances are continually taken into and
- This is the movement of molecules or ions through. transported out of the cell according to need.
from an area of HIGH CONCENTRATION - This allows the polar molecules to pass When a substance is taken into a cell, the process
to an area of LOW CONCENTRATION through because they are water-soluble. required is called endocytosis and exists in two
until EQUILBRIUM is reached. - Each channel protein is specific to one forms, pinocytosis (drinking) and phagocytosis
- Molecules move randomly. type of ion.
When a substance is removed from the cell, the
- The rate of diffusion can be affected by - They may also open and close as the cell process required is Exocytosis.
several factors such as catalysts and requires the entrance and exit of these
temperature. molecules. Phagocytosis:
This is referred to as cell eating.
Factors Affecting Diffusion: Osmosis and Water Potential: The cell sometimes needs to obtain material that is
- The size of the CONCENTRATION Osmosis is the movement of water molecules from too large to be transported by diffusion or active
an AREA OF HIGH WATER POTENTIAL TO AN transport.
AREA OF LOW WATER POTENTIAL through a A lyosome fuses with the transport vesicle, digests
- An increase in temperature adds kinetic selectively permeable membrane.
energy to molecules. its contents and than the useful products are
absorbed into the cytoplasm.
- Length of diffusion path. Water Potential: White blood cells called phagocytes destroy
- Thickness of cell membrane. The term WP is used to describe the tendency f bacteria and remove the cell debris by this method.
water molecules to move from high to low
- Surface area of molecule. concentrations of water. Pinocytosis:
Water moves from an area of high WP to an area of This is cell drinking. The entries of a liquid into the
low WP. cell via the same mechanism as phagocytes but
This method is used to help the particles and ions
Water Potential = pressure potential + solute with smaller vesicles are produced.
that would not usually be able to pass through the
The pressure potential is a force developed on the Exocytosis:
This problem occurs due to molecules not being
cell wall that opposes the hydrostatic pressure build This is the method used by cells to transport
up through water entering the sap vacuole by substances OUT of the cell.
Carrier Proteins or Channel Proteins in the
osmosis. Mostly a positive figure. Vesicles transport the substances to the cell
membrane help these molecules to pass through.
The Solute potential is the concentration of membrane from the Golgi and they are then
dissolved sugars/salts in a solution. despatched outside of the cell.
A higher solute potential lowers the water potential Digestive enzymes are secreted this way.
- These proteins help the diffusion of sugars of a solute. VICE VERSA/
and amino acids.
- The molecule wishing to diffuse must attach Turgor and Plasmolysis: This is the only method of transport that requires
to the protein at the binding site. Hypertonic Solution- high water potential and low energy in the form of ATP.
- This distorts the shape of the protein solute potential. Ions and molecules are moved against their
which allows the molecule to pass through Hypotonic Solution- low water potential and high concentration gradient from a LOW to HIGH
the membrane. solute potential. concentration.
Isotonic Solution- EQUAL.
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As energy for active transport is supplied by ATP
made in respiration, anything that decreases
respiration will decrease active transport
mechanisms. Such as respiratory inhibitors like
This process occurs by using carrier proteins.…read more