1. Cell Membrane & Passive Transport:
EQ: Can I diagram diffusion of oxygen, facilitated diffusion of glucose, and osmosis across a cell membrane?

2. BOUNDARY OF THE CELL
Cell: smallest unit that can carry out all the activities for life. (the “atom” of biology)

3. Cell Membrane Outside of cell Inside of cell (cytoplasm) Carbohydrate
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

4. Membrane structure
Fluid Mosaic Model—Proteins “float” in a fluid or moveable layer of phospholipids
Semi-Permeable—certain molecules can pass through the membrane, but not all molecules can

5. The Structure of the Cell Membrane
Outside
of cell
Inside
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains
Proteins—act as channels or pumps to help molecules pass through the membrane
Carbohydrate chains—help cells recognize and communicate with each other
Phospholipid bilayer—
phospholipids have a phosphate head (yellow circle)
lipid tails (the brown tails).
The phosphates line up on the outside because they are hydrophilic (water-loving).
The lipid tails line up on the inside because they are hydrophobic (water-hating).

6. Review of solution terms:
Solution – mixture of solute and solvent
Solute – substance being dissolved
Solvent – substance dissolving solute
(Universal Solvent)-Water

7. Membrane traffic
Passive transport~ diffusion of a substance across a biological membrane (NO ENERGY)
[] = concentration
Diffusion~ the overall movement of particles from a region of high [] to an area of low []
Osmosis~ the diffusion of water across a selectively permeable membrane

8. Results of Diffusion Dynamic equilibrium Homeostasis
Once diffusion has evenly distributed the solute throughout the solvent; movement of particles continues with no change in []
Homeostasis
Preservation of equilibrium

9. Diffusion depends on [] gradient
[] gradient: the difference in [] of a substance across space
Diffusion is said to move down a [] gradient
Diffusion continues until there is NO [] gradient
Ex: O2 diffuses into oxygen depleted blood

10. Diffusion
Small molecules like WATER, OXYGEN, AND CARBON DIOXIDE can move in and out freely.
Large molecules like PROTEINS AND CARBOHYDRATES CANNOT
Charged IONS CANNOT

11. Osmosis~ the diffusion of water across a selectively permeable membrane

12. Osmosis in the Real World
Bryophytes, or mosses, are plants that depend on osmosis transfer water from the environment into the plant.
Bryophytes can never grow tall, because they cannot pull the water against gravity just using the concentration gradient.
Bryophytes must also live in wet environments

13. Questions Osmosis is the diffusion of _______ across a cell membrane.
Osmosis and Diffusion are both types of __________ transport.
Passive transport does or does not require energy?
Small molecules can not move across freely. T or F
Large molecules can move freely. T or F

14. Three Different Types of Solutions
Isotonic Solution
Hypotonic Solution
Hypertonic Solution

15. Isotonic Solution
The solute outside the cell is equal in concentration to the solute in the cell.
The cell retains its shape.
water moves equally in both directions

16. Hypotonic Solutions
Solution outside the blood cell contains a lower [] of solute than inside of the cell.
Water will diffuse in.
cell will lyse (burst).
Animal cells - cytolysis.
Plant cells do not burst- turgur pressure— grocers use this idea

17. Cells in a Hypotonic Solution

18. Hypertonic Solutions
The solution outside the cell has a higher [] of solute than inside of the cell.
Water will diffuse out of the cell,
causing the cell to shrink
or crenate
Why should you not salt meat before cooking?
CRENATION PLASMOLYSIS

19. Cells in a Hypertonic Solution

20. In what type of solution would these cells be found?

21. Water Balance Summary Osmoregulation~ control of water balance
Hypertonic~ higher concentration of solutes
Hypotonic~ lower concentration of solutes
Isotonic~ equal concentrations of solutes

22. Plasmolysis Turgidity in plant cells.

23. What type of solution is this?
Hypertonic
What will happen to the cell?
It will shrink.