1. FL #8 Cell Membranes and Semipermeability Know that cells are enclosed within semipermeable membranes that regulate what enter and leave the cell. Cell Biology Standard 1A October 22-23, 2003 Tony Gonzales

2. (Cell Biology 1A) The function of the cell membrane? A. Breaks down lipids, carbohydrates, and proteins from food. B. Stores water, salts, proteins, and carbohydrates. C. Keeps the cell wall in place. D. Regulates which materials enter and leave the cell.

3. The following slides show the different means by which materials move in and out of the cell and other semi-permeable membrane.

4. The cartoon to the right illustrates passive diffusion. Diffusion is when material moves from high to low concentration. The dashed line is intended to indicate a membrane that is permeable to the molecules or ions illustrated as red dots. Initially all of the red dots are within the membrane. As time passes, there is net diffusion of the red dots out of the membrane, following their concentration gradient. When the concentration of red dots is the same inside and outside of the membrane the net diffusion ceases. However, the red dots still diffuse into and out of the membrane, but the rates of the inward and outward diffusion are the same resulting in a net diffusion of O.

6. Shown to the right is an animation which illustrates protein mediated, facilitated diffusion out of a cell. Facilitated diffusion= Is when proteins act as channels to facilitate the movement of material in or out of the cell.

7. Shown to the right is an animation illustrating how secretion vesicles approach the plasma membrane, fuse with the plasma membrane and dump their soluble contents outside of the cell. This process is called exocytosis and it is mechanism by which cells can secrete molecules like proteins. For example, the epithelial cells in the breast use secretion vesicles to put the major protein of milk (casein) outside of the cell which synthesized it. Facilitated Diffusion

8. Active Transport-When materials move across a cell membrane against a concentration difference. When materials move from an area of low concentration to an area of high concentration.

9. 1. (Cell Biology 1A) An animal cell that is surrounded by fresh water will burst because the osmotic pressure causes? A.Water to move into the cell through the cell membrane. B.Water to move out of the cell through the cell membrane. C.Solutes to move into the cell through the cell membrane. D.Solutes to move out of the cell through the cell membrane. Cell Osmosis- is when water move from high to low concentration across a membrane.

10. 2. (Cell Biology 1A) Which of the following is a function of the cell membrane? A. Breaks down lipids, carbohydrates, and proteins from food. B. Stores water, salts, proteins, and carbohydrates. C. Keeps the cell wall in place. D. Regulates which materials enter and leave the cell.

11. 3. (Cell Biology 1A) During diffusion materials move? A.From high to low concentration. B.From low to high concentration. C.Across the membrane with the assistance of a protein. D.Across the membrane with the assistance of a lipid.

12. 4. (Cell Biology 1A) Active transport moves materials? A.From high to low concentration. B.From low to high concentration. C.Across the membrane with the assistance of a protein. D.Across the membrane with the assistance of a lipid.

13. 5. (Cell Biology 1A) Facilitated diffusion is when materials move? A.From high to low concentration. B.From low to high concentration. C.Across the membrane with the assistance of a protein. D.Across the membrane with the assistance of a lipid.