Cell Transport
I. Cell Membrane
• The cell membrane regulates
what enters and leaves the cell
and also provides support and
protection.
I. Cell Membrane
• The composition of nearly all cell
membranes is a double-layered sheet
called a lipid bilayer.
• The lipids are called phospholipids.
• In addition to lipids, most cell
membranes contain protein molecules
that are embedded in the lipid bilayer.
I. Cell Membrane
• Carbohydrate molecules are
attached to many of these proteins.
• Some of the proteins form channels
and pumps that help move material
across the cell membrane.
• Many of the carbohydrates act like
chemical identification tags,
allowing individual cells to identify
one another.
II. Basic Vocabulary
• Solution: two or more
substances mixed
together
• Solvent: the substance
in which a solute is
dissolved to form a
solution (ex. water)
• Solute: a substance that
is dissolved in a solvent
to form a solution (ex.
salt)
• Concentration: the
amount of a solute in a
given solution
III. Passive Transport
• The movement of molecules without
the use of energy down the
concentration gradient (from an area
of high concentration to an area of
low concentration
• 3 Types
III. Passive Transport
• Diffusion: the
movement of
small molecules
(such as carbon
dioxide and
oxygen) through
the cell
membrane.
III. Passive Transport
• Osmosis: the diffusion of water
through the cell membrane.
• With osmosis, three types of
solutions can occur.
III. Passive Transport:
Osmosis-Types of Solutions
A. Isotonic: “Same strength” The concentration
of solutes is the same inside and outside the
cell. Water moves equally in and out of the
cell.
III. Passive Transport:
Osmosis-Types of Solutions
B. Hypertonic: “above
strength” The
solution has a
higher solute
concentration than
the cell. Water will
move out of the cell
causing it to shrivel.
III. Passive Transport:
Osmosis-Types of Solutions
• C. Hypotonic: “below strength” The
solution has a lower solute concentration
than the cell. Water will move into the
cell causing it to swell.
III. Passive Transport:
Facilitated Diffusion
• Facilitated
Diffusion: the
movement of large
molecules such as
glucose through the
cell membrane
using protein
channels or pumps.
IV: Active Transport
• The movement of molecules using
energy (in the form of ATP) up the
concentration gradient (from an area
of low concentration to an area of
high concentration).
IV: Active Transport
• Endoyctosis: the process
of taking material into the
cell. The cell membrane
extends and wraps around
the material pulling it into
the cell.
– Phagocytosis: cell eating
– Pinocytosis: cell drinking
• Exocytosis: the process of
releasing material from the
cell.