This document discusses different types of transport mechanisms in cells. There are two main types: passive transport, which moves materials down their concentration gradient without cellular energy expenditure, and active transport, which moves materials against their concentration gradient using cellular energy. Passive transport includes diffusion, facilitated diffusion, and osmosis. Osmosis specifically refers to the diffusion of water molecules through a semipermeable membrane down its concentration gradient. Active transport requires ATP and includes endocytosis, exocytosis, and transport across membranes via carrier proteins.

1. Transport Mechanism
Jelo Hagos

2. 2 Types of Transport Mechanisms
1. Passive transport – is the direction of
movement of materials is from where they
are more concentrated to where they are less
concentrated.
2. Active transport – involves carrier molecules
and cellular energy of ATP that against yjeir
concentration gradient.

3. 2 Types of Passive Transport
1. Diffusion – involves the spontaneous and
random movement of molecules from one
place to another. They move from a region
where they are more concentrated to a
region where they are less concentrated.

4. Examples of Diffusion

5. 2 Types of Passive Transport
1. Diffusion –The difference in concentration
between these two regions is called
concentration gradient. Diffusing molecules
tend to move in greater number down the
concentration gradient called net diffusion.
Once equilibrium is attained, net diffusion
stops. In other words, net diffusion is said to
be equal to zero.

6. 2 Types of Passive Transport
1. Diffusion

7. Query!!!
• In equilibrium state of diffusion, Is
net diffusion stopping? Is diffusion
stopping?
Answer: It is net diffusion, not
diffusion itself, that stops at
equilibrium.

8. 2 Types of Passive Transport
1. Diffusion – may also take place through
membranes. A permeable membrane is one
that allows both solvent and solute molecules to
pass through it.
Sample Problem
Assume that container A contains a 20% sugar
solution and container B contains 10% sugar
solution. Assume further that equal volumes of the
two solutions are present on either side of the
membrane. What will be the diffusion of the
molecules through membrane?

9. 2 Types of Passive Transport
2. Osmosis – is a special term used for the diffusion
of solvent molecules through a differentially
permeable membrane, that makes two solutions
separated. The net osmotic movement will stop
when equilibrium reaches.
Sample problem
Assume further that equal volumes of sugar
solutions were placed in container A and B.
However, container A had 10% sugar solution while
container B had 20% sugar solution. What will
happen in Osmosis process?

10. Query!!!
Does cell membrane undergo in
osmosis or diffusion?
Answer: Both

11. 2 Types of Passive Transport
2. Osmosis
Hypotonic solution contains lower
concentration of dissolved materials than the
cell. In other words, the concentration of water
in the solution is greater than in cell.

12. 2 Types of Passive Transport
2. Osmosis
Hypertonic solution contains higher
concentration of solutes than the cell. That is,
the concentration of water in the solution is
lower than in the cell.

13. 2 Types of Passive Transport
2. Osmosis
Isotonic solution contains concentration of
the water molecules is the same as that in the
cell. The cell neither swells nor shrinks.

14. Query!
Osmosis specifically involves the movement of
water molecules down the concentration gradient
through a differentially permeable membrane.
1. If molecules of a solute (like sugar) pass through
a differentially permeable membrane, what is
the process called?
2. If molecules of a solvent (like water) pass
through a permeable, what is the process
called?
3. What primary factor determines the direction of
osmosis?

15. 2 Types of Passive Transport
3. Facilitated Diffusion – the passage of
molecules through the cell is aided by certain
carrier proteins. It is also known as carrier-
assisted transport.

16. Types of Active Transport
1. Endocytosis – involves the entry into the cell
of materials that are too large to get in by the
mere diffusion.
2 types of endocytosis
1. Phagocytosis – is the process by which a
cell engulfs or takes in solid particles that are
too large to enter the cell by diffusion. (white
blood cells and amoeba)
2.Pinocytosis – is the process of taking in
fluids by cells.

17. Types of Active Transport

18. Types of Active Transport
1. Exocytosis – ,the reverse of endocytosis, is
the process by which a cell expels large
molecules, such as proteins and
polysaccharides.

19. Types of Active Transport
1. Exocytosis – ,the reverse of endocytosis, is
the process by which a cell expels large
molecules, such as proteins and
polysaccharides.

20. Activity
1. Distinguish between a) diffusion and
osmosis; b) facilitated diffusion and active
transport.
2. Foods treated with salt or sugar have longer
shelf life. Explain the reason for using salt
and sugar as food preservatives.

21. References:
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