Download Cell Membranes and Transport

Cell Membranes and Transport
Go to
Section:
Slide # 2
About Cell Membranes
1.All cells have a cell membrane
2.Functions:
a.Regulates what enters and
exits the cell
b.Provides protection for the
cell
c.Supports the cell
TEM picture of a
real cell membrane.
Slide # 3
Structure of cell membrane
1. phospholipid bi-layer (2 membranes)
a.Phosphate head is polar (water loving)
b.Fatty acid tails non-polar (water
fearing)
c.Proteins embedded in membrane
Slide # 4
Structure of the Cell Membrane
Cell membrane has pores (holes) in it
a.Selectively permeable: Allows some
molecules in and keeps other molecules out
b.Structure is related to its function!
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
Slide # 6
Types of Passive Transport
1. Diffusion: molecules
move from area of high
concentration to area of
lower concentration
a.Occurs in living & nonliving things
b.Passive transport
c.Does not use energy
for it to occur
Diffusion continues until all
molecules are evenly spaced
Slide # 7
Types of Passive Transport
2. Facilitated diffusion:
movement of specific
molecules (glucose) across
cell membranes through
protein channels
a.Protein channels are
specific – only allow certain
molecules across
b.Passive – does not use
energy to move glucose
c. Movement occurs from
high to lower concentration
Facilitated
diffusion
Diffusion
Slide # 7
Facilitated Diffusion
Molecules move through a protein channel from high
to lower concentration
High
Concentration
Glucose
molecules
Cell
Membrane
Low
Concentration
Go to
Section:
Protein
channel
Slide # 9
Types of Passive Transport
3.Osmosis: movement of
water from area of high
concentration to area of
lower concentration
a.Diffusion of water
b.Occurs in living & nonliving things
c.Passive – does not use
energy
•Water moves freely
through pores.
•Solute (green) too
large to move across.
Slide # 10
Hypotonic Solution
Hypotonic: The solution has a lower
concentration of solutes and a higher
concentration of water than inside the cell.
Result: Water moves from the solution to inside
the cell): Cell Swells and bursts open (lyses)!
Slide # 11
Hypertonic Solution
Hypertonic: The solution has a higher
concentration of solutes and a lower
concentration of water than inside the cell.
Result: Water moves from inside the cell into
the solution: Cell shrinks! (Plasmolysis)
Slide # 12
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!
Protecting Against Osmotic Pressure
1. Bacteria and plant cells have cell walls to prevent the cell
from expanding and bursting when placed in a hypotonic
solution. Plants use osmotic pressure turgor pressure to
keep from wilting.
2. Single celled eukaryotes (paramecium, amoeba) use a
contractile vacuole to pump excess water out of their
cells to keep from bursting open.
3. Salt water fish have specialized salt-pumping cells so
they will not dehydrate in their salt water ocean, which is
hypertonic to their cells.
4. Our cells are constantly bathed in blood (isotonic). Our
lungs and kidneys get rid of excess water in our body so
our blood can always be isotonic to the rest of our cells.
Slide # 13
Types of Active Transport
1. Active transport:
movement of molecules
from area of lower to
higher concentration
a.Movement against a
concentration
gradient
b.Requires energy
from the cell
Protein changes shape to
move molecules: this
requires energy!
Slide # 14
Types of Active Transport
2. Endocytosis: taking
material into a cell
a.Cell membrane in-folds
around food particle
b.“cell eating”
c.forms food vacuole &
digests food
d.This is how white blood
cells eat bacteria!
e.Uses energy
Slide # 15
Types of Active Transport
3. Exocytosis:
membrane surrounding
the material fuses with
cell membrane
a.Forces material out
of cell
b.Cell changes shape
– requires energy
c.EX: Hormones
exported from cell
Slide # 13
Cell Membrane: Just Passing Through