1. Cell Transport
Different Methods used by Cells to Move Molecules into or out of the Cell

2. Active vs. Passive Transport
The different methods of moving molecules across membranes can be divided into two groups, depending on whether they require energy or not.
Active Transport will not happen unless the cell uses energy to move the molecule.
Passive Transport happens automatically without needing energy.
Atp 4
NRG!!!

3. Concentration Gradients
The concentration of a liquid describes the amount of a substance dissolved in it.
“Solvent” = liquid that has molecules dissolved in it
Low Concentration
High Concentration
“Solute” = molecule dissolved in a liquid
A gradient describes the difference between two things – so the concentration gradient is the amount of difference in the concentration inside and outside of the cell.

4. Inside Cell
Outside Cell
Cell Membrane
Both diagrams show the inside of the cell has fewer dissolved molecules than the outside
Greater Concentration
Gradient
Top diagram has a bigger difference between the inside and outside of the cell
Lesser
Concentration
Gradient
Inside Cell
Outside Cell
Cell Membrane

5. Hypotonic vs. Hypertonic
If molecules are more concentrated inside the cell than outside, we say that the cell is in a hypotonic solution (“hypo” means low).
If molecules are more concentrated outside the cell than inside, we say the cell is in a hypertonic solution (“hyper” means high).
Cell in a hypotonic solution
Cell in a hypertonic solution

6. Gradients & Energy
Molecules “want” to equalize concentrations inside and outside the cell.
If they can equal out by moving from high to low concentration (“downhill”), no energy is required and passive transport occurs.
If they need to move from low to high concentration to equal out, energy is required and active transport is needed to move the molecules “uphill” against the concentration gradient.

7. No energy needed to move from high to low – passive transport
Outside Cell
Inside Cell
Energy required to move from low to high – active transport

8. Types of Passive Transport
Diffusion: molecules just cross the membrane from high to low concentration. They must be small enough to squeeze between the phospholipids, like oxygen & CO2.
Facilitated Diffusion: molecules cross from high to low, but they are too big to squeeze through, so they need help from a channel protein.
Osmosis: water moves across the membrane from high H2O to low H2O concentration. This is tricky because the H2O concentration is the opposite of the molecule’s concentrations!

9. 2% sugar solution (Low concentration) 98% water
Osmosis
2% sugar solution (Low concentration) 98% water
5% sugar solution
(High concentration)
95% water
What happens to a cell in these two solutions if the cell has 3% sugar?

10. Osmosis cell = 3% sugar 97% water
5% sugar solution
(High concentration)
95% water
Hypertonic solution
2% sugar solution (Low concentration) 98% water Hypotonic solution
cell = 3% sugar
97% water
Water enters cell by osmosis & cell swells up
Water exits cell by osmosis & cell shrinks

11. Types of Active Transport
Active transport usually refers to the cell using energy from ATP to power a carrier protein that moves molecules in or out.
Exocytosis is when the golgi bodies use vesicles to send molecules out of the cell.
Endocytosis is when a cell wraps its membrane around a particle and “swallows” it into a vacuole. If it is a large particle, it is called phagocytosis (cellular eating), if it is a small particle it is called pinocytosis (cellular drinking)

12. Exocytosis

13. Endocytosis