There are three main types of movement across cell membranes: passive transport, which does not require energy and includes diffusion, osmosis, and facilitated diffusion; endocytosis and exocytosis, which allow materials to enter and exit cells through membrane vesicles; and active transport, which uses energy to transport molecules against their concentration gradient using carrier proteins. Whether water moves into or out of a cell depends on if the external solution is isotonic, hypotonic, or hypertonic relative to the cell.

1. TYPES OF MOVEMENT ACROSS
THE CELL MEMBRANE

2. Passive Transport
 Passive transport is the movement of molecules
across the cell membrane and does not require
energy.
 It is dependent on the permeability of the cell
membrane.
 There are three main kinds of passive transport -
Diffusion, Osmosis and Facilitated Diffusion.

3. Diffusion
 The movement of molecules from a region of higher concentration to a
region of lower concentration.

4. Facilitated diffusion
 This process does not require ATP but does require cell
membrane proteins which are called carrier proteins to carry
the molecules across the cell membrane from an area of higher
concentration to an area of lower concentration

5. Osmosis
 The movement of water across a semi permeable membrane.
 Osmosis is the movement of water (red dots) through a
semipermeable membrane to a higher concentration of solutes
(blue dots).

6. How Do Hypotonic, Hypertonic, and Isotonic
Solutions
Affect the Water Movement of a Cell?

7. Hypertonic
Solution
A Hypertonic solution contain a high concentration of
solute in relation to the solution within the cell (e.g. the
cell's cytoplasm).
When a cell is placed in a hypertonic solution, the water
diffuses out of the cell, causing the cell to shrivel up.

8. Hypotonic
Solution
A hypotonic solution contain A solution with a
lower salt concentration than in normal cells
When a cell is placed in a hypotonic solution,
the water diffuses into the cell, causing the cell
to swell and possibly explode.

9. Isotonic
Solution
A solution that has the same salt
concentration as the normal cells of the
body and the blood.
When a cell is placed in an isotonic
solution, the water diffuses into and out of
the cell at the same rate. The fluid that
surrounds the body cells is isotonic.

10. Isotonic, Hypotonic, and Hypertonic Solutions
 Water moves readily across cell membranes through special protein-lined
channels, and if the total concentration of all dissolved solutes is not equal
on both sides, there will be net movement of water molecules into or out of
the cell. Whether there is net movement of water into or out of the cell and
which direction it moves depends on whether the cell’s environment is
isotonic, hypotonic, or hypertonic.

11. Isotonic, Hypertonic, and Hypotonic Solutions

12. Cell membranes are permeable to water, therefore, the environment the cell is
exposed to can have a dramatic effect on the cell.

13. Moving other Materials and Substances into and out of the cell
 ENDOCYTOSIS-Endo (within)
cytosis (cell) ) is a process in
which a substance (e.g. proteins)
gains entry into a cell without
passing through the cell
membrane.
• EXOCYTOSIS-Exo (exit) cytosis
(cell) ) is a process in which a
substance is exited from the cell
without passing through the cell
membrane.
• Examples of things that migth
be exited include secretion of
proteins like
enzymes, hormones and
antibodies.

14. Active Transport
 Active Transport requires the cell to use energy, usually in the form of ATP.
 Active Transport creates a charge gradient in the cell membrane. For
example in the mitochondrion, hydrogen ion pumps pump hydrogen ions
into the intermembrane space of the organelle as part of making ATP.

15. Active Transport
Active Transport keeps unwanted ions or other molecules out of the cell that are able to
diffuse through the cell membrane.

16. Active Transport
 Active transport uses energy to send substances against the direction they
would travel by simple diffusion: that is from a region of low concentration
to a region of high concentration.