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What is a solute?
What is a solvent?
What is diffusion and osmosis?
What does it mean to be active?
What does it mean to be selective?
What is a sac?
What is a receptor?
What do the prefixes aqua-, endo-, and
exo- mean?
 Solution
– a homogenous mixture of
two or more components in which the
solute (thing that is dissolved) does
not settle out of the solvent.
 Intracellular fluid – fluid inside the
cells
 Interstitial fluid – fluid outside the
cell
 Both fluids contain various solutes
from gases, nutrients and salts
 Selective
permeability – a barrier
allows some substances to pass
through but excludes others
 Passive Transport Processes –
substances are transported across the
membrane without any energy input
from the cell
 Active Transport Processes – cell have
to provide the energy to complete the
transport process
A
movement of particles and molecules
from an area of high concentration to areas
of low concentration
 Cell use simple diffusion – the unassisted
diffusion of solutes through the plasma
membrane. These particles have to be
either
1) Small enough to pass through the pores
(ions)
2) Can dissolve in the fatty portion of the
membrane (fats, oxygen, carbon dioxide)
 Diffusion
of water through selectively
permeable membranes
 In the cell, this occurs in special pores
called aquaporins, which are created by
proteins in the membrane
 If
molecules are too large to fit through
pores or cannot dissolve into the fatty
portion of the membrane, they may have
to move through a protein membrane
channel or may have to use a carrier
protein to complete their movement from
high to low concentrations.
 Forcing
water and solutes through a
membrane.
 In this case, a pressure gradient actually
pushes solute containing fluid from a
higher pressure to a lower pressure.
Uses ATP
 An
active process in which special
carrier proteins use ATP to move
molecules against their concentration
gradients
 Examples
• Moving large amino acids and sugars into the
cell
• The sodium-potassium pump – moves sodium
out and potassium in
 Exocytosis
– moves substances out of the
cell by packaging the substances in sacs,
allowing them to move to the cell
membrane, where the sac fuses with the
membrane and the contents of the cell are
ejected.
 Endocytosis – into the cell. Materials
outside the cell are “captured” by part of
the membrane, which surrounds the
material and allows it to move into the cell
in a sac.
 Phagocytosis
– “cell eating”, a protective
process, specific phagocytes meet up with a
sac, fuse with it, and digest the contents
 Pinocytosis – fluid-phase endocytosis.
Allows a cell to take in fluids
 Receptor-mediated endocytosis – receptors
on the cell membrane target certain
molecules, that once they bind to the target,
endocytosis occurs to move the target into
the cell