1. Active and Passive Transport
Chapter 5

2. 1. Passive Transport Movement of materials in and out of the cell
Requires no energy to happen

3. Two Types of Passive Transport
Diffusion: When substance moves that is dissolved in water
Osmosis: When water moves across the membrane

4. Solutions are made of 2 parts:
Solute: Substance that is dissolved in water
Solvent: Liquid it is dissolved in (usually water)

5. Vocab: Hypertonic: More solutes than the other solution
Hypotonic: Less solutes than the other solution
Isotonic: Equal solutes as another solution

6. Membrane (cross section)
Osmosis
Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Equilibrium
(b)

7.  Lower concentration of solute (sugar) Higher of sugar
Same concentration
Selectively
permeable mem-
brane: sugar mole-
cules cannot pass
through pores, but
water molecules can
More free water
molecules (higher
concentration)
Water molecules
cluster around
sugar molecules
Fewer free water
molecules (lower
Water moves from an area of higher
free water concentration to an area
of lower free water concentration 
Osmosis

8. Describing a solution
Hypotonic: when a solution is less concentrated than another solution
Example: if around a cell is hypotonic, then water will move into the cell.
Can cause a cell to get so large it may burst (cytolysis)

9. Hypertonic: When a solution is more concentrated than another solution
If around a cell is hypertonic, water will move out of the cell
Can cause the cell to get very small (in plants will see plasmolysis: wilting)

10. Isotonic: when two solutions have the same concentration (are at equilibrium)
Causes water to move in and out equally
The cell maintains its shape

11. Hypotonic solution
Isotonic solution
Hypertonic solution
(a)
(b)
H2O
Lysed
Normal
Shriveled
Turgid (normal)
Flaccid
Plasmolyzed

12. Osmosis
Water moves trying to balance out concentrations
Goes from where there is more water to less water

13. What if…..
Environment around a cell is hypotonic. What direction will the water move?
Salt?

14. What if….. The environment around a cell is hypertonic.
What direction will the water move?
Salt?

15. 2. Active Transport Requires energy
Goes against the concentration gradient (from lower concentration to higher concentration)

16. Figure 7.16 The sodium-potassium pump: a specific case of active transport
Cytoplasmic Na+ binds to
the sodium-potassium pump. 1
Na+ binding stimulates phosphorylation by ATP. 2
K+ is released and Na+
sites are receptive again;
The cycle repeats. 3
Phosphorylation causes the
protein to change its conformation, expelling Na+ to the outside. 4
Extracellular K+ binds to the
protein, triggering release of the
Phosphate group. 6
Loss of the phosphate
restores the protein’s
original conformation. 5
EXTRACELLULAR
FLUID
[Na+] high
[K+] low
CYTOPLASM
[Na+] low
[K+] high
Na+ P
ATP
ADP
P i K+

17. Sodium Potassium Pump
Cells usually have more sodium ions outside and more potassium ions inside
Pump increases number of ions where concentration is already high

18. When substances are too large to pass through the cell membrane, use endocytosis or exocytosis
Membrane folds around substances and release into cell or out of cell

19. Figure 7.20 Exploring Endocytosis in Animal Cells
EXTRACELLULAR
FLUID
Pseudopodium
CYTOPLASM
“Food” or
other particle
Food
vacuole
1 µm
of amoeba
Bacterium
Food vacuole
An amoeba engulfing a bacterium via
phagocytosis (TEM).
PHAGOCYTOSIS
PINOCYTOSIS
Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM).
0.5 µm
Plasma
membrane
Vesicle

20. Endocytosis Material moved into cell Forms vesicle
Pinocytosis: Liquids
Phagocytosis: Solids

21. Exocytosis
Material released to outside of cell