1. Cell Membrane n The cell membrane or plasma membrane completely surrounds the cell and serves as a barrier between the cell and its environment. n Allows entrance of needed substances (glucose, amino acids, lipids, etc.) and prevents entrance of other substances. n Allows waste products (CO 2 ) to exit the cell

2. n The cell membrane allows some molecules to enter the cell but prevents entrance of other molecules. n The cell membrane retains certain molecules inside the cell but allows other molecules to exit. n Therefore, the cell membrane is said to be selectively permeable to molecules.

3. n Lipid molecule = 1 glycerol + 3 fatty acids n Phospholipid molecule = 1 glycerol + 1 phosphate group + 2 fatty acids n The head region of the phospholipid is also called the polar region and is hydrophilic (water loving) n The tail region of the phospholipid is also called the nonpolar region and is hydrophobic (water hating) n The cell membrane is composed of a phospholipid bilayer.

4. The cell membrane is composed of a phospholipid bilayer. n The heads of the bilayer can interact with water because they are polar. n The tails of the bilayer cannot interact with water because they are nonpolar. n Therefore, water soluble molecules cannot move through the bilayer easily.

5. Transporting across the cell membrane - Passive Transport - Active Transport Passive Transport - does not require energy - moves from an area of high concentration to an area of low concentration ( a downhill flow) There are two types of cellular transport that occurs across the cell membrane.

6. Passive Transport (con’t) n Passive transport includes - diffusion - facilitated diffusion - osmosis n Diffusion- occurs when molecules move randomly away from each other in a liquid or gas. Example: sugar/water salt/water smoke/air

7. Passive Diffusion moves from an area of high concentration to an area of low concentration ( a downhill flow)

8. Diffusion (con’t) n Diffusion is the continual moving about and bumping of particles into each other. This continues until all the particles of a substance are equally distributed throughout the container. However, the bumping never stops!

9. Facilitated Diffusion

10. Passive Transport

11. Osmosis n Osmosis is the diffusion of WATER across a semi- permeable membrane n osmosis occurs in response to the concentration of solutes dissolved in water. n Water moves low solutes to high solutes A simple rule to remember is: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

13. Osmosis in a Isotonic solution n If the concentration of a solute (salt) is equal of on both sides, the water will move back in forth but it won't have any result on the overall amount of water on either side. "ISO" means the same

14. Animation of Osmosis (Cell in an Isotonic Environment ) Outside of Cell Inside of Cell Equal number of solutes inside and outside of cell Cell will remain same

15. Osmosis in a Hypertonic solution n The word "HYPER" means more, in this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction.In plant cells, the central vacuole loses water and the cells shrink, causing wilting.

16. Osmosis Animation (Cell in Hypertonic Environment) Outside of Cell Inside of Cell Higher percent of solutes outside of cell Cell will shrivel

17. Osmosis in a Hypotonic Solution n The word "HYPO" means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell. The cell will gain water and grow larger. In plant cells, the vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting

18. Osmosis Animation (Cell in Hypotonic Environment) Inside of Cell Outside of Cell Lower percent of solutes outside of cell Cell will swell

20. Osmosis in action

21. Facilitated Diffusion n a process whereby a large substance passes through a membrane with a aid of a facilitator. n The facilitator is an integral membrane protein that spans the width of the membrane. n The force that drives the molecule from one side of the membrane to the other is the force of diffusion.

22. Active Transport n Energy is needed in active transport n Active transport is the movement from an area of low concentration to an area of high concentration (uphill flow) n Active transport use carrier proteins that act as pumps.

23. Active Transport Active transport is the movement from an area of low concentration to an area of high concentration (uphill flow)

24. Active Transport (con’t) n Active transport include: Bulk Transport Bulk Transport is for solutes to large to cross a cell membrane. Examples: endocytosis exocytosis

25. Endocytosis n During endocytosis the cell membrane Folds into a pouch that encloses the particles. The pouch pinches off INSIDE the Cell to form VESICLE (membrane-wrapped bubbles). The VESICLE can then fuse with other Organelles (LYSOSOMES) or Release its contents into the Cytoplasm.

26. Endocytosis con’t(Pinocytosis & Phagocytosis) n Pinocytosis and Phagocytosis are two types of endocytosis. Pinocytosis is sometimes referred to as “cell drinking” n Solutes or Fluids outside the Cell Membrane can be brought into the Cytoplasm by pinocytosis. Pinocytosis takes in liquids

27. Pinocytosis Pinocytosis is the ingestion of dissolved materials by endocytosis. The cytoplasmic membrane folds in and pinches off placing small droplets of fluid in a pinocytic vesicle. The liquid contents of the vesicle is then slowly transferred to the cytosol.

28. Phagocytosis n Phagocytosis is like pinocytosis except the cell engulfs a food particle or other cells instead of a drop of liquid. n "CELL EATING" Phagocytosis takes in solid particles

29. Phagocytosis Phagocytosis is the ingestion of solid particles by endocytosis. The cytoplasmic membrane folds in and pinches off placing the particle in a phagocytic vacuole. The phagocytic vacuole then fuses with lysosomes and the material is degraded.

30. Exocytosis n During exocytosis waste and cell products leave the cell. Products made in the cell are packaged in golgi vesicles, which then fuse with the cell membrane and secrete material out of the cell.

31. Exocytosis During exocytosis, a cell releases waste products or specific secretion products by the fusion of a vesicle with the cytoplasmic membrane.

32. How active transport occurs