1. Moving Substances Across Cell Membrane
cell membrane is semi–permeable
Some molecules pass through easily, some need help
Some molecules pass through without the expenditure of energy (spontaneous) and some require an input of energy (ATP)
What molecules move IN and OUT of a cell:
Small nonpolar molecules (CO2, O2)
Small polar molecules such as water
Ions and charged molecules
Large polar molecules (eg. Glucose)
Macromolecules
Movement IN and OUT can
Be PASSIVE or ACTIVE

2. Passive Transport [High][Low] cell uses no energy
molecules move randomly
Molecules spread out from an area of high concentration to an area of low concentration.
[High][Low]
Three types:
Diffusion
Facilitative Diffusion
Osmosis
high
low
Weeee!!!

3. Simple Diffusion Animation
Passive Transport:
Diffusion: random movement of particles from an area of [high] to an area of [low].
diffusion continues until all molecules are evenly spaced (equilibrium is reached)-
Note: molecules will still move around but stay spread out.

4. Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)
Passive Transport: A B
2. Facilitated diffusion: diffusion of particles from [H  L] through transport proteins found in the membrane
Transport Proteins are
specific – they “select” only
certain molecules to cross
the membrane
Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

5. Passive Transport:
Osmosis animation
3.Osmosis: diffusion of water through a selectively permeable membrane from an area of [H  L]
Water moves freely through pores.
Solute (green) too large to move across.

6. Effects of Osmosis on Life
Water molecules are so small and so numerous that cells can’t control movement of water through the cell membrane.
So what determines the direction of water movement?
The environment around the cell,
…specifically,
the concentration of water molecules inside the cell compared to outside
Environment around the cell is either:
HYPOTONIC, ISOTONIC, HYPERTONIC

7. But first - Don’t confuse Volume of water with Concentration
Equal Volumes, Different Concentration

8. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Hypotonic: The external environment (ECF) has a lower concentration of solutes and a higher concentration of water than inside the cell.
Result: Water moves from the ECF to inside the cell
- Cell Swells and bursts open (cytolysis)!

9. Compare a blood cell in an isotonic environment with one in a hypotonic environment

10. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Isotonic Solution
Isotonic: The concentration of solutes in the ECF is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size. (Dynamic Equilibrium)

11. Water on the way out

12. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
Hypertonic Solution
Hypertonic: The ECF has a higher concentration of solutes and a lower concentration of water than inside the cell.
shrinks
Result: Water moves from inside the cell into the solution: Cell shrinks. Plasmolysis (plant cell) Crenation (animal cell)

13. B C A In what type of solution are these cells? Hypertonic Isotonic
Plant cells resist bursting. Why?
Hypertonic
Isotonic
Hypotonic

14. Active Transport cell uses energy
Animations of Active Transport & Passive Transport
Active Transport
cell uses energy
actively moves molecules to where they are needed
Movement of molecules from an area of [low] to an area of [high]
Three Types
Protein Pumps
Endocytosis
Exocytosis
high
low
This is gonna be hard work!!

15. Types of Active Transport
Sodium Potassium Pumps (Active Transport using proteins)
1. Protein Pumps –are special transport proteins that help move molecules IN/OUT - require energy to do work
example: Na+/K+ Potassium Pumps are important in nerve responses.
Protein changes shape to move molecules: this requires energy!

16. Types of Active Transport
2. Endocytosis: taking bulky material into a cell
Uses energy
Cell membrane folds itself around food particle
“cell eating”
forms food vacuole & digests food
This is how white blood cells eat bacteria!

17. Types of Active Transport
3. Exocytosis: Forces material out of cell in bulk
membrane surrounding the material fuses with cell membrane
Cell changes shape – requires energy
EX: Hormones or wastes released from cell
Endocytosis & Exocytosis animations

18. Endocytosis_[
Active_Transport_~~_[