Download Transport across the cell membrane

I.The Cell Membrane
A. Controls what enters and leaves the cell
B. Provides structure and support
C. Most cell membranes are made of a
double layered sheet called a
phospholipid bilayer.
Figure
7-15
The
Structure of the
The
Cell
Membrane
Cell Membrane
Section 7-3
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
A semi permeable membrane means that some substance can pass across
the membrane and others cannot. The cell membrane is a semi-permeable
Gomembrane
to
Section:
Solution vs. Solutes
• A solution is a liquid mixture of two or
more substances and are evenly mixed.
• The dissolved substance is called the
solute.
• A solvent dissolves the solute
• Solvent + Solute = Solution
Examples: Salt water, sugar water,
Passive Transport
• Transport across the cell membrane that
does not require energy.
Diffusion
• Diffusion is the tendency of molecules to
move from an area of high concentration
to an area of low concentration.
Diffusion
• Molecules move
from an area of
high
concentration to
an area of low
concentration.
Diffusion
• A semi permeable membrane means
that some substance can pass across the
membrane and others cannot.
• The cell membrane is made up of a semipermeable membrane
•
Diffusion
Some molecules, such as water, can cross the
cell membrane by diffusion.
Diffusion
•
When the concentration of a solute is the
same through out a solution, the system
has met equilibrium.
Diffusion
• Cells constantly maintain equilibrium in
any system they are in and molecules are
always passing in and out of the lipid
bilayer even when equilibrium is met.
• Equilibrium- When the concentration of a
solute is the same through out a solution,
the system has met equilibrium.
Example of Diffusion
Osmosis
• Osmosis is the diffusion of water through a
selectively permeable membrane.
Review Osmotic Pressure
Effect when cell is placed in…
HYPO TONIC
HYPERTONIC
ISOTONIC
video
Hypotonic: The solution has a HIGHER concentration of water than the
concentration of water inside the cell therefore water will GO INTO the cell and
the cell increases in size.
Isotonic: The solution has an EQUAL concentration compared to the inside
of the cell therefore no water would move in or out and the cell would remain
the SAME size and shape.
Hypertonic: The solution the cell is has a LOWER concentration of water
than the concentration of the water inside the cell therefore water would
MOVE OUT the cell and the cell would shrink
Active Transport
Active Transport
•
•
Material moves from an area of lower
concentration to an area of higher
concentration in a process called active
transport.
Active transport is the movement
across the cell membrane that requires
energy in the form of ATP.
How is this different than passive
transport?
Forms of Active Transport
• Endocytosis- the process of taking in
material into the cell by means of
infoldings, or pockets, of the cell
membrane.
Forms of Active Transport
• Exocytosis- is the removal of large
amounts of material from the cell.
Two Methods of Transport
Passive Transport
Without Energy
1. Diffusion
2. Osmosis
Active transport
With Energy
1. Endocytosis
2. Exocytosis