Download Diffusion

Diffusion: Movement of particles from an area of
high concentration to low concentration.
– Concentration & permeability are the factors that
determine if diffusion occurs across a membrane or
not.
Concentration: The amount of dissolved solute
(substance) in a volume of solvent (liquid).
– Solution = solvent + solute
– If a substance is present in unequal amounts on
either side of a membrane, it will move to the area of
lower concentration until equilibrium is reached.
Permeability: How well a substance can pass
through something such as a membrane.
– ↑ membrane permeability allows more in/out
– ↓ membrane permeability allows less in/out
PASSIVE TRANSPORT
• Passive transport: Movement of materials in or
out of the cell which does NOT require use of
cell energy (ATP).
– Cells live in a liquid environment which makes it easier
for materials (food, water, gases) to move in & out of the
cell.
– 2 types: Osmosis & facilitated diffusion
Vorticella
Osmosis: Diffusion of H2O molecules through a
semi-permeable membrane from an area of ↑
H2O concentration to ↓ H2O concentration.
– 3 types of solutions (hypertonic, isotonic, hypotonic)
Osmotic pressure: The force exerted by osmosis,
that moves water across a semi-permeable
membrane from a diluted solution to a more
concentrated solution.
– Occurs in hypotonic, isotonic, & hypotonic solutions
Hypertonic solution: An osmotic solution
(outside cell) where solute concentration is
higher than the concentration inside the cell.
H2O leaves cell; Cell shrinks.
– ↑ solute in solution, ↓ solute in cell
– Plasmolysis: The shrinking of the cytoplasm due to
the loss of H2O.
Isotonic solution: An osmotic solution (outside cell)
where the solute concentration is equal to the
solute concentration inside the cell. H2O enters/
exits cell at an even rate. Cell doesn’t shrink or
expand. Ideal conditions.
– solute in solution ↔ solute out of cell
Hypotonic solution: An osmotic solution (outside
cell) where the solute concentration is lower than
the solute concentration inside the cell. H2O
enters cell; Cell expands.
– ↓ solute in solution, ↑ solute in cell
– Cytolysis: The bursting of a cell.
HYPOTONIC
ISOTONIC
HYPERTONIC
FACILITATED DIFFUSION
Facilitated diffusion: The transport of materials
across the plasma membrane by means of transport
proteins.
1. Channel proteins
2. Carrier proteins
Channel Protein: Tube-like proteins in the cell
membrane through which small, dissolved
particles can diffuse.
Aquaporin: A special type of channel protein that
moves water in & out of the cell
quickly.
Carrier proteins: A protein in the cell membrane
whose shape fits a specific molecule or ion.
– When the proper molecule binds with the protein,
the protein changes shape and moves the molecule
across the membrane.
ACTIVE TRANSPORT
Active transport: The movement of materials
against the concentration gradient.
– Molecules move from ↓ concentration to ↑ concentration
• Chemical energy (ATP) from the cell is used to
change the shape of a protein to move molecules
across the cell membrane.
ENDOCYTOSIS
Endocytosis: A process in which a cell surrounds
& takes in material from its environment.
– A vacuole is then produced and taken into the cell.
endocytosis
Phagocytosis: A form of endocytosis in which
the cell will take in large food particles into
the cell.
Pinocytosis: A form of endocytosis in which
the cell takes liquids into the cell.
EXOCYTOSIS
Exocytosis: A process in which the cell removes
large particles or wastes
exocytosis