1. Which is heavier, one hundred pounds of feathers, or one hundred pounds of bricks?

2. Cell Boundaries

3. Macromolecules in cells! All the cell parts are made up of these macromolecules We will start with just looking at cell boundaries

4. What organelle allows molecules to pass from outside the cell to inside the cell? Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

5. The Cell Membrane All cells are bound by a cell membrane. The Cell membrane consists of: Lipid bilayer [Phospholipid bilayer] Proteins Carbohydrates Cholesterol

6. Cell Walls lay outside the cell membrane. They are rigid and made of carbohydrates Present in: –Plant cells –Fungi –Bacterial cells

7. Cell membrane is semi-permeable - it allows certain things across but restricts other things The structure of the cell membrane fits its function –Flexible barrier –Semi-permeable –Sends and receives chemical messages from other cells

8. Membrane Structure

9. To Recap… Phospholipids are water resistant and flexible Carbohydrates are like ID tags for the cell Proteins are for stability and act like passageways for substances to enter and leave the cell.

10. Diffusion Diffusion: The movement of a molecule, or atom from an area of high concentration to an area of low concentration until equilibrium is reached –Equilibrium means equal concentrations on both sides of the membrane –This naturally occurs and normally no energy is required Diffusion video

11. Glucose Molecules will move from an area of high concentration to the area of low concentration.

12. Osmosis: the movement of water across a semi permeable membrane

14. 1. Isotonic solution The same concentration of solute on both sides of the membrane Water will continue to move into and out of the cell at an EVEN RATE

15. Water moves in AND out!

16. Hypotonic Solution outside solution has a lower concentration of solute than inside the cell (Higher concentration of water outside the cell) Result: Water will move into the cell These red blood cells are in a hypotonic solution and have gained water

17. Hypertonic Solution outside solution has a higher concentration of solute than inside the cell (Lower concentration of water outside the cell) Results: Water moves out of the cell These Red blood cells are in a hypertonic solution and have lost water

19. Click on Image to watch video

20. Click on image to watch video

22. Facilitated Diffusion I.Movement of a molecule across a membrane when protein channels are required. II.Sometimes molecules are too large to pass or they are charged and can’t pass through the membrane without help 1.When a protein channel helps a molecule this is called Facilitated diffusion 2.Protein channels are specific for one kind of molecule

23. Active Transport Movement of molecules from low concentration to high concentration. (This is the opposite of diffusion)

24. 1) Molecular transport 1.Used for small ions such as calcium, potassium and sodium 2.Must pump ions across the membrane (This requires ENERGY!!) 3.Involves changes in protein shape Active Transport: Types

25. 2) Endocytosis –For transport of larger molecules into the cell –Occurs with pockets of the cell membrane that fold into the cells creating a vacuole that is released into the cytoplasm –A vacuole is a bubble- shaped part of the cell used for storage Active Transport: Types

26. 2 types of Endocytosis a ) Phagocytosis : “cell eating”- cells take up particles and form a food vacuole

27. Pinocytosis: “Cell drinking”- cells take up liquid from the surrounding environment.

28. Exocytosis Release of materials from the cell