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Crazy scientist Says…
*Answer the following questions in complete sentences.
How is a window screen similar to a cell membrane?
Answer the following in your response:
– What are some things that can pass through a window
screen?
– What are some things that cannot pass through a window
screen?
– Why is it important to keep these things from moving
through the screen?
– The cell is surrounded by a cell membrane, which
regulates what enters and leaves the cell. Why is it
important to regulate what moves into and out of the cell
Life is Cellular
Cell Boundaries
Cell Membrane
• The Cell Membrane is made up of a lipid
bilayer.
• It has two functions:
1. Regulates what enters and leaves the cell.
This is called SELECTIVE PERMEABILITY.
2. Provides support and protection.
Permeate
• To spread, or pass through
Selective Permeability
• SELECTIVE PERMEABILITY is caused by
the way PHOSPHOLIPIDS in the cell
membrane interact with water:
– Phospholipid (lipid) has a polar “head” on the
outside (likes water - hydrophilic) and two
(fatty acids) nonpolar “tails” on the inside
(hates water - hydrophobic).
PHOSPHATE
GROUP
2 FATTY
ACIDS
Selective Permeability Cont…
• SELECTIVE PERMEABILITY is also caused
by the MEMBRANE PROTEINS in the lipid
bilayer.
• Substances can move in and out of the cell by
traveling through these proteins.
– Kind of like a tunnel or gate
Cell Communication
• Cells must communicate with each other!
•Nutrition - Feed Me
- Need for nutrients to run efficiently.
•Hormone Regulator - Regulate Me
- Regulate temperature, metabolism.
•Cleansing/Excretion - Cleanse Me
- Need for excretion of waste/toxins.
•Host Defense - Repair Me
- Need for damage repair and renewal.
•Defense Cell - Defend Me
- Need for help from specialized defense
cells, i.e. white blood cells.
•Identification - See Me
- Cells communicate such things as their
structure, location and function e.g. "I'm a
liver cell, and here's what I do."
Cell Communication Cont…
• Cells that do not lie next to each other
cannot communicate directly.
• Signal molecules are released to carry
information to nearby cells.
• MEMBRANE PROTEINS help
communication between cells and carry
substances in and out of the cell:
– Peripheral proteins – sit on the surface of the
membrane. (many)
– Integral proteins – cross through the
membrane…hard workers! (few)
Types of Membrane Proteins
• MARKER PROTEINS:
– Go through the cell membrane and serve to identify
the cell they occupy.
– The immune system uses these proteins to tell
friendly cells from foreign invaders.
– They are as unique as fingerprints.
– They play an important role in organ transplants. If
the marker proteins on a transplanted organ are
different from those of the original organ the body
will reject it as a foreign invader.
Types of Membrane Proteins Cont…
• RECEPTOR PROTEINS:
– These proteins are used for communication in
the cell – allows cells to communicate.
– The receptor protein releases a signal to
perform some action – muscle contraction.
Types of Membrane Proteins Cont…
• TRANSPORT PROTEINS: regulates what
enters or leaves the cell.
1. CARRIER PROTEINS
do not extend all the way
through the membrane.
They move specific
molecules through the
membrane one at a time.
2. CHANNEL PROTEINS
extend through the lipid bilayer.
They form a pore through the
membrane that can move
molecules in several ways.
Other “Stuff” in the Membrane
• CHOLESTEROL:
– Steroids are sometimes a component of cell
membranes in the form of cholesterol. When it
is present it reduces the fluidity of the
membrane. Not all membranes contain
cholesterol.
Cell Transport
• The cell membrane has to regulate the
movement of molecules from one side of
the membrane to the other.
• Molecules move by:
–
–
–
–
Passive Transport – no energy required
Active Transport – energy required
Endocytosis
Exocytosis
Cell Transport Cont…
• Passive
Transport –
diffusion of
molecules
without the use
of energy.
Cell Transport
Passive & Active Transport
• Facilitated
diffusion (no
energy) – glucose
molecules cannot
diffuse across the
membrane on
their own. Carrier
proteins move
glucose molecules
through protein
channels.
Cell Transport
• Hypertonic –
water diffuses
OUT of the cell
(cell shrinks).
• Hypotonic –
water diffuses
INTO the cell
(cell swells).
• Isotonic – water
diffuses into and
out of the cell at
EQUAL rates
(cell stays the
same).
Cell Transport Cont…
• Active Transport –
the diffusion of
molecules with the
use of energy.
– Sodium Potassium
Pump – most
important
membrane pumps
in animal cells.
Carrier protein
carries 3 Na out
and 2 K in.
– ATP is the energy
needed to move
molecules against
their concentration
gradient.
Cell Transport Cont…
• Endocytosis –
taking in material
by pockets of the
cell membrane
(vesicles).
– Phagocytosis –
white blood cell
eating bacteria.
• Exocytosis –
releasing large
amounts of
material (vesicle).
Bio I
• For your OUTPUT you will be recreating
the following types of transport:
–
–
–
–
–
–
–
–
Passive
Active
Diffusion
Osmosis
Facilitated diffusion
Hypertonic solution
Hypotonic solution
Isotonic solution