The document discusses three forms of passive transport that allow substances to move across cell membranes from areas of higher to lower concentration without energy expenditure: simple diffusion, facilitated diffusion through protein channels, and osmosis which is the diffusion of water molecules through membrane channels. It provides examples of each type of passive transport and explains how cells are affected by solutions that are isotonic, hypotonic, or hypertonic in terms of water movement and cell volume.

1. To:
Dr. N. Karthik
Assistant Professor
Department of Microbiology
Sacred Heart college, Tirupattur.
Presented by:
SALOMI V (BP211509)
I M.sc Applied Microbiology
Department of Microbiology
Sacred Heart college, Tirupattur.
UPTAKE OF NUTIENTS BY CELLS:
PASSIVE TRANSPORT

2. PASSIVE TRANSPORT / UPTAKE
In passive process substances cross the membrane from
an area of higher concentration to an area of lower
concentration by the cell.
There are three forms of passive uptake /
transport.
1. Simple diffusion
2. Facilitated diffusion
3. Osmosis

3. 1. SIMPLE DIFFUSION

4. 2. Facilitated Diffusion
Facilitated Diffusion is that molecules move from high solute concentration to low solute concentration
through a protein channel.
The movement of larger molecules like glucose through the cell membrane – larger molecules must be
“helped”.
NO ENERGY IS NEEDED = PASSIVE TRANSPORT
 Facilitated Diffusion in Prokaryotes
EXAMPLE: Glycerol EXAMPLE: Suger, Aminoacid & Vitamins
( Non- specific transport) (specific transprot)
 Facilitated Diffusion in Eukaryotes

5. 3.Osmosis
Osmosis is the net movement of solvent molecules across a
selectively permeable membrane from an area with a high
concentration to an area of low concentration.
Water crosses cell membrane via special channels called
“Aquaporins”.
Osmosis : Diffusion of water.

6. ISOTONIC SOLUTION
 Water concentration is equal inside and outside the cell, thus rates
of diffusion are equal in both directions.
 No net moment of water.

7. Hypotonic solution
 Water moves into the cell.
 If the Cell wall is strong, the cell swells and
 If the cell is weak or damage, the cell bursts (Osmotic lysis).

8. Hypertonic solution
 Water moves out of the cell and
 the cell becomes shrink (Plasmolysis).