5. Simple Diffusion
Diffusion is the net movement of molecules (or ions) from
a region of their high concentration to a region of their lower
concentration.
The molecules move down a concentration gradient (via
kinetic energy present in molecules). As a result of
diffusion, molecules reach an equilibrium where they are
evenly spread out.
This is when there is no net movement of molecules from
either side.
8. Factors Affecting the Rate of
Diffusion
The bigger the
difference between
the two sides of the
membrane the
quicker the rate of
diffusion.
Steepness of the
concentration
gradient
Temperature
Higher
temperatures
give molecules
or ions more
kinetic energy.
Molecules
move around
faster, so
diffusion is
Surface area
The greater the
surface area the
faster the diffusion
can take place.
This is because
more molecules or
ions can cross the
membrane at any
Type of molecule
or ion diffusing
Large molecules
need more energy
to get them to
move so they tend
to diffuse more
slowly.
9. Molecules that diffuse through
cell membranes
Polar but also very
small so diffuses
quickly.
Water
Carbon
Dioxide
Polar but very
small so diffuses
quickly.
Oxygen
Non-polar so
diffuses very
quickly.
10. Facilitated Diffusion
FACILITATED DIFFUSION is involved when large polar
molecules
(glucose and amino acids) and ions (Na+ or Cl-) pass
through protein channels.
Movement of molecules is still PASSIVE just like ordinary
diffusion, the only difference is, the molecules go through a
protein channel instead of passing between the
phospholipids.
15. Osmosis
The diffusion of water from an area of high
concentration of water molecules (high water
potential) to an area of low concentration of water
(low water potential) across a partially permeable
membrane.
17. Tonicity
Hypotonic Solution
Isotonic Solution
Hypertonic Solution
having a higher concentration of water
molecules in the environment than inside the
cell.
having equal concentrations of water
molecules in the environment and inside the
cell.
having a lower concentration of water
molecules in the environment than
inside the cell
02
01
03
21. Active Transport
The uphill movement of the substances against the
concentration gradient requiring some kind of
energy is known as ACTIVE TRANSPORT.
It is accomplished by special transmembrane proteins
known as CARRIER PROTEINS.
26. Vesicular Transport
• Vesicles and vacuoles that fuse with the cell
membrane may be utilized to release or transport
chemicals out of the cell or to allow them to enter
a cell.
• Vesicles are formed by budding off from the cell
membrane or from the membranous organelles of
the cell.
• These move to their target sites and fuse with the
target membrane to release their contents.
27.
28. Endocytosis
PINOCYTOSIS
It is the process by which
macromolecules (e.g.
protein molecules) are
taken up by the cell along
with a small quantity of
PHAGOCYTOSI
S
It is the process by
which large particles
like cell debris and
bacteria are engulfed
by phagocytic cells.
RECEPTOR-
MEDIATED
This process depends on the
presence of receptor proteins
called CARGO PROTEINS in the
cell membrane. The cargo
proteins bind to LIGANDS which
come in contact with the cell
It is a process in which the membrane itself wraps
around the particle and pinches off a vesicle inside
the cell.
Channel proteins are transport proteins that act like pores (tunnel or openings) in the cell membrane that lets water molecules or small ions through quickly.
Water Channel proteins (Aquaporins)
Ion Channel proteins
Carrier Proteins are transport proteins that undergo binding to the molecule, resulting to the movement of the molecule through the membrane.
the capability/strength of a solution to modify the volume of cells by altering their water content.
Carrier Proteins
Cargo proteins Any protein that is carried within the vesicles of a cell's secretory system
