Decription about cell membrane transport

1. AS Biology, Cell membranes and
Transport 1
Transport Across cell
membranes
CLASS- B.Sc. I SEM- II

2. AS Biology, Cell membranes and
Transport 2
Content:-
 Structure of the Cell Membrane
 DIFFUSION and FACILITATED DIFFUSION
 OSMOSIS
 ACTIVE TRANSPORT
 BULK TRANSPORT

3. AS Biology, Cell membranes and
Transport 3
Outside of cell
Inside of cell
(cytoplasm)
Lipid
Bilayer
Proteins
Transport
Protein Phospholipids
Carbohydrate
chains
Structure of the Cell Membrane
Animations
of membrane
structure

4. AS Biology, Cell membranes and
Transport 4
Transport through cell
membranes
 The phospholipid bilayer is a good barrier around cells,
especially to water soluble molecules. However, for the cell to
survive some materials need to be able to enter and leave the
cell.
 There are 4 basic mechanisms:
1. DIFFUSION and FACILITATED DIFFUSION
2. OSMOSIS
3. ACTIVE TRANSPORT
4. BULK TRANSPORT

5. AS Biology, Cell membranes and
Transport 5
Types of Cellular Transport
 Passive Transport
cell doesn’t use energy
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis
 Active Transport
cell does use energy
1. Protein Pumps
2. Endocytosis
3. Exocytosis
high
low
This is
gonna
be hard
work!!
high
low
Weeee!!
!
•Animations of Active
Transport & Passive
Transport

6. AS Biology, Cell membranes and
Transport 6
Simple Diffusion
 Diffusion is the net movement of molecules (or ions)
from a region of their high concentration to a region of
their lower concentration.
 The molecules move down a concentration gradient
 Diffusion continues until all molecules are evenly
spaced (equilibrium is reached)-
1) SIMPLE DIFFUSION

7. AS Biology, Cell membranes and
Transport 7
SIMPLE DIFFUSION
Diffusion is a PASSIVE process which means no energy is used
to make the molecules move, they have a natural kinetic energy.

8. AS Biology, Cell membranes and
Transport 8
2) 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.

9. AS Biology, Cell membranes and
Transport 9
 Diffusion of specific particles through transport
proteins found in the membrane
 Transport Proteins are specific – they
“select” only certain molecules to cross
the membrane
 Transports larger or charged molecules
Facilitated
diffusion
(Channel Protein)
Diffusion (Lipid
Bilayer)
Facilitated Diffusion
Carrier Protein
A B

10. AS Biology, Cell membranes and
Transport 10
Molecules that diffuse through cell membranes
1. Oxygen – Non-polar
so diffuses very
quickly.
1. Carbon dioxide –
Polar but very small
so diffuses quickly.
2. Water – Polar but
also very small so
diffuses quickly.

11. AS Biology, Cell membranes and
Transport 11
 The diffusion of water from an area of
high concentration of water molecules
(high water potential) to an area of low
concentration of water (low water
potential) across a partially permeable
membrane.
 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.
Osmosis
3. Osmosis

12. AS Biology, Cell membranes and
Transport 12
Osmosis
Cell membrane
partially
permeable.
Inside cell Outside cellVERY High conc.
of water
molecules. High
water potential.
VERY Low conc.
of water
molecules. High
water potential.
Sugar molecule
DILUTE SOLUTION
CONCENTRATED SOLUTION

13. AS Biology, Cell membranes and
Transport 13
Active Transport
cell uses energy
actively moves molecules to where they are needed
Movement from an area of low concentration to an area of
high concentration
(Low  High)
Three Types:
1) Proton Pumps
2) Endocytosis
3) Exocytosis

14. AS Biology, Cell membranes and
Transport 14
Active Transport1) 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!

15. AS Biology, Cell membranes and
Transport 15
Cotransport also uses the process of diffusion. In this case a molecule that is moving
naturally into the cell through diffusion is used to drag anothermolecule into the cell.
In this example glucose hitches a ride with sodium.
Glucose Cotrasportor

16. AS Biology, Cell membranes and
Transport 16
Receptor Proteins
These proteins are used in intercellular communication. In this
animation you can see the a hormone binding to the receptor. This
causes the receptor protein release a signal to perform some action.

17. AS Biology, Cell membranes and
Transport 17
2. Endocytosis:
taking bulky material into a cell
• Uses energy
• Cell membrane in-folds around
food particle
• “cell eating”
• forms food vacuole & digests
food
• This is how white blood cells eat
bacteria!

18. AS Biology, Cell membranes and
Transport 18
3) Exocytosis:
Forces material out of cell in bulk
• membrane surrounding the material
fuses with cell membrane
• Cell changes shape – requires
energy
• EX: Hormones or wastes released
from cell
Endocytosis & Exocytosis

19. AS Biology, Cell membranes and
Transport 19
4) Vesicle-mediated transport
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.