1. Cell Membrane
11/16/10

2. Cell Membrane Function Importance
Controls what enters and exits the cell.
Importance
By regulating this movement it helps the cell to maintain homeostasis.

3. Homeostasis
Maintaining a constant internal state in a changing environment.
All living things respond to their environment
Cells maintain homeostasis by limiting the movement of substances across the cell membrane
Acts as a gatekeeper

4. Cell Membrane Structure Phospholipid bilayer Carrier Proteins
Hydrophilic heads
Hydrophobic tails
Carrier Proteins
Help transport through membrane

5. Solutions In solutions, moving molecules fill up a space.
Equilibrium is when the concentration of a substance is the same throughout a space.
When there is a difference in the concentration of a substance, a concentration gradient exists.
This concept will be important when talking about some of the vocabulary.

6. Movement Across Membranes
Two types of transport
Passive Transport
Requires no energy to occur
Active Transport
Requires energy to occur
Boat Analogy

7. Types of Passive Transport
Diffusion
Movement of a substance from high concentration to low concentration
Diffusion of water is referred to as osmosis.
Facilitated Diffusion
Uses carrier proteins to help the substances diffuse through the cell membrane.

8. Diffusion

9. Osmosis
Predicting the movement of water depends on the concentration of the cell’s environment
Solutions can have three different concentrations:
Hypertonic: Higher concentration outside the cell.
Isotonic: Concentration is the same inside and outside the cell.
Hypotonic: Lower concentration outside the cell.

10. Osmosis Practice Saltwater solution
What is the solute?
What is the solvent?
Water is the substance moving through the membrane.
Which way will the water move?
98% Saltwater

11. Osmosis Practice Saltwater solution
What is the solute?
What is the solvent?
Water is the substance moving through the membrane.
Which way will the water move?
2% Saltwater

12. Osmosis Practice Sugarwater solution
What is the solute?
What is the solvent?
Water is the substance moving through the membrane.
Which way will the water move?
15% Sugarwater

13. Active Transport
In active transport, substances are being transported against their concentration gradient.
Requires energy
Molecules move from an area of lower concentration to an area of higher concentration

14. Active Transport Cell Membrane Pumps
Proteins that move molecules through the cell membrane

15. Active Transport Endocytosis Exocytosis
Movement of molecules into the cell through a vesicle
Exocytosis
Movement of molecules out of the cell through a vesicle