Download The Cell Membrane

Cellular Transport
Notes
About Cell Membranes
1.All cells have a cell
membrane
2.Functions:
a.Controls what enters
and exits the cell to
maintain an internal
balance called
homeostasis
b.Provides protection and
support for the cell
About Cell Membranes (continued)
3.Structure of cell membrane
Lipid Bilayer -2 layers of
phospholipids
a. Phosphate head is polar (water
loving)
b. Fatty acid tails non-polar (water
fearing)
c. Proteins embedded in membrane
d. Steroids and cholesterol are
embedded within the cell
membrane.They provide support
and flexibility.
Phospholipid
Lipid Bilayer
Polar heads Fluid Mosaic
love water
Model of the
& dissolve. cell membrane
States that the membrane
is in constant motion
Non-polar
tails hide
from water.
Carbohydrate cell
markers
Proteins
About Cell Membranes (continued)
• 4. Cell membranes have pores (holes) in it
a.Selectively permeable: Allows some
molecules in and keeps other molecules out
b.The structure helps it be selective!
Pores
Cell Membrane
Cholesterol in the Membrane
Structure of the Cell Membrane
Outside of cell
Proteins
Lipid
Bilayer
Transport
Protein
Animations
of membrane
Go to structure
Section:
Carbohydrate
chains
Phospholipids
Inside of cell
(cytoplasm)
Cell Transport
• There are three types of cellular transport
– Passive Transport
– Active Transport
– Cytosis
Types of Cellular Transport
•
•
Weeee!!!
Passive Transport
cell doesn’t use energy
1. Diffusion
2. Facilitated Diffusion
3. Osmosis
•Animations of Active
Transport & Passive
Transport
high
low
Active Transport
cell does use energy
1. Protein Pumps
2. Endocytosis Cytosis
3. Exocytosis
This is
gonna
be hard
work!!
high
low
Passive Transport:
1. Diffusion
Simple Diffusion
Animation
1. Diffusion: random movement
of particles from an area of
high concentration to an
area of low concentration.
(High to Low)
•
Diffusion continues until all
molecules are evenly spaced
(equilibrium is reached)-Note:
molecules will still move around
but stay spread out.
http://bio.winona.edu/berg/Free.htm
What determines the rate of diffusion?
There 4 factors:
1. The steepness of the concentration gradient. The bigger
the difference between the two sides of the membrane
the quicker the rate of diffusion.
2. Temperature. Higher temperatures give molecules or ions
more kinetic energy. Molecules move around faster, so
diffusion is faster.
3. The surface area. The greater the surface area the faster
the diffusion can take place. This is because the more
molecules or ions can cross the membrane at any one
moment.
4. The type of molecule or ion diffusing. Large molecules
need more energy to get them to move so they tend to
diffuse more slowly. Non-polar molecules diffuse more
easily than polar molecules because they are soluble in the
non polar phospholipid tails.
Passive Transport
• The diffusion of water is called OSMOSIS.
Passive Transport - Osmosis
A good way to remember which way water
will move is to remember that the water
will ALWAYS move TOWARDS the solutes
(salt).
Passive Transport:
3. Osmosis
Osmosis
animation
• 3.Osmosis: diffusion of
water through a
selectively permeable
membrane
• Water moves from high
to low concentrations
•Water moves freely
through pores.
•Solute (green) to large
to move across.
Passive Transport
• We have special names for the different
types of situations where osmosis occurs
in cells.
Passive Transport
• We have special names for the different
types of situations where osmosis occurs
in cells.
Hypotonic Solution
Hypotonic: The solution has a lower concentration of
solutes and a higher concentration of water than
inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the
cell): Cell Swells and bursts open (cytolysis)!
Hypertonic Solution
Hypertonic: The solution has a higher concentration
of solutes and a lower concentration of water than
inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the
solution: Cell shrinks (Plasmolysis)!
Isotonic Solution
Isotonic: The concentration of solutes in the solution
is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and
the cell remains same size! (Dynamic Equilibrium)
What type of solution are these cells in?
A
B
C
Hypertonic
Isotonic
Hypotonic
Summary
• Isotonic Solutions are those where the
concentration of the solution EQUALS the
concentration of the cell.
• Hypertonic Solutions are those where
the concentration of the solution is MORE
than the concentration of the cell.
• Hypotonic Solutions are those where the
concentration of the solution is LESS than
the concentration of the cell.
What is the solution?
40% Salt
10% Salt
Hypotonic
10% Salt
40% Salt
Hypertonic
15% Salt
15% Salt
Isotonic
What is the cell?
40% Salt
10% Salt
Hypertonic
10% Salt
40% Salt
Hypotonic
15% Salt
15% Salt
Isotonic
Remember!
In osmosis,
goes towards the
!
Passive Transport:
Facilitated Diffusion
Facilitated diffusion:
diffusion of specific particles
through transport
proteins found in the
membrane
a.Transport Proteins are
specific – they “select”
only certain molecules
to cross the membrane
b.Transports larger or
charged molecules
A
B
Facilitated
diffusion
(Channel
Protein)
Diffusion
(Lipid
Bilayer)
Carrier Protein
Passive Transport: 2. Facilitated Diffusion
Glucose
molecules
Cellular Transport From aHigh Concentration
High
Cell Membrane
Low Concentration
Through a 
Transport
Protein
Protein
channel
Low
Facilitated Diffusion:
• Molecules will randomly move through
the opening like pore, by diffusion. This
requires no energy, it is a PASSIVE
process. Molecules move from an area
of high concentration to an area of low
conc.
Active Transport
• Active transport is when the cell
membrane “imports” or “exports”
substances that are needed that do not
travel by diffusion.
• Usually, this means obtaining substances
against the concentration gradient
• Substances go from areas of LOW
concentration to areas of HIGH
concentration
Active Transport
Types of Active Transport
1. Protein Pumps transport proteins that
require energy to do
work
•Example: Sodium /
Potassium Pumps
are important in nerve
responses.
Sodium
Potassium Pumps
(Active Transport
using proteins)
Protein changes
shape to move
molecules: this
requires energy!
Active Transport
• Active Transport uses energy called ATP.
• Active Transport = ATP
• Accomplished by the proteins embedded
within the cell membrane.
Active Transport
• The lack of efficient pumps can be classified as
a disease.
– Sodium Deficiency can cause muscle spasms, and
Liddie's Syndrome.
– Potassium deficiencies can cause an irregular heart
beat, epileptic seizures in infancy, and deafness.
• Examples of active transport include:
–
–
–
–
Kidney's removing sodium
Thyroid obtaining iodine
Gills removing salt from water
Plants obtaining minerals through the roots.
Summary
Cytosis: A type of Active Transport
• Large amounts of some substances can
be taken in and out of a cell directly by the
membrane.
Endocytosis
Exocytosis
Types of Active Transport
•
Endocytosis:
– Uses energy (ATP)
• Cell membrane in-folds around
food particle
• Endocytosis of large particles is
called phagocytosis, “cell eating”
• Endocytosis of small particles is
called Pinocytosis, “cell drinking”
• forms food vacuole & digests food
• This is how white blood cells eat
bacteria!
Phagocytosis
Your white blood cells can keep you
healthy by using PHAGOCYTOSIS
The LYSOSOMES digest the bacteria
cell and then spit it out of the cell.
Types of Active Transport
3. Exocytosis:
 movement of material out of
cytoplasm of the cell using
ATP
• membrane surrounding the
material fuses with cell
membrane (like endocytosis
backwards)
• how cells get rid of wastes
Endocytosis &
Exocytosis
animations
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. Exocytosis is the term applied when transport is out of the
cell.