Cell transport involves the movement of substances into and out of cells through passive or active transport. Passive transport includes diffusion, osmosis, and facilitated diffusion which do not require energy. Active transport uses energy from ATP to move substances against a concentration gradient or into cells through ion pumps and endocytosis/exocytosis. Substances move across membranes through concentration gradients in passive transport or with the help of transport proteins in active transport.

1. Cell Transport
Movement of substances in and out of
cells

2. Substances move in and out of cells by:
1. Passive transport
2. Active transport

3. Passive Transport
No energy (ATP) is required to move gas or liquid
molecules from one place to another!
(Is this an example of a “free lunch” or perpetual motion?… imagine if our cars
worked like this….)
Need to understand concepts of :
• Diffusion,
• Osmosis,
• Concentration gradient,
• Net movement

4. Diffusion
• The random movement of molecules from
an area of high concentration to an area of
low concentration.
• Down the concentration gradient.
• Animation
• Animation2 Conc. Grad

5. Rate (speed) of diffusion depends on:
» fast slow
Size of molecules
Temperature
State of matter
Concentration gradient

6. Osmosis
• Net movement of water molecules from an
area of high water concentration to an
area of low water concentration, through a
semi-permeable membrane.
• Animation Animation2
• Hypertonic – more solute and less water
• Hypotonic – less solute and more water
• Isotonic – same conc. of solute and water

7. Think (don’t write)
• Most marine fish die if
transferred to freshwater.
• When a drop of blood is
mixed with distilled water, the
blood cells burst.
• Living plant tissues that had
lost water become firm when
supplied with water.

8. Net movement
The overall movement of all molecules of a
substance back and forward along the
concentration gradient.
e.g. when oxygen or water molecules diffuse
into a cell, some molecules move out at
the same time. Overall more are moving
inwards than outwards so the net
movement is………..

9. Osmoregulation
• The control of water in a cell.
• Plasmolysis –
– Water leaves cell and membrane shrinks from
wall.
– Cell becomes flaccid.
– Full plasmolysis is irreversible.
Animation

10. • Turgor
– Water enters cell causing it to swell
– Cell becomes turgid
– Cell wall prevents rupture
• Animation

11. Active Transport
Energy (ATP) is required for:
Endocytosis (phago- and pino-),
Exocytosis,
Ion pumps
• e.g. re-absorption of glucose by kidney,
salt uptake by the roots of plants, amino
acid uptake by fungi

12. • The movement of substances from an
area of low concentration to an area of
high concentration.
• Against the concentration gradient
Conc. Grad

13. Cytosis
1.Endocytosis
• Movement in (enter) to a cell
• Phagocytosis – cell eating – forms a food
vacuole.
• e.g. Lysosomes fuse to enable digestion.
• Pinocytosis – cell drinking – forms a
vesicle
• e.g. Amoeba and white blood cells (WBC)
– pseudopodia
• Animation

14. 2.Exocytosis
• Movement out (exit)
• Vesicles bud off from golgi apparatus or
ER, vacuole fuses with cell membrane and
expels contents
• Secretions e.g. digestive enzymes
released, glands
• Animation

15. Ion Pumps
• Proteins in the cell membrane can actively
accumulate specific ions on one side of
the membrane to control the amount
• Animation
• Animation2