It Is Better to Keep Your Mouth Closed and Let People Think You Are a Fool Than to Open

“It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.” ~Mark Twain (1835 - 1910)~

Name: ______

1. The two most important functions of the plasma membrane are:

1.

2.

2. The best definition of Homeostasis is:

a) Keeping a constant temperature inside a cell or organism despite external changes.

b) Keeping constant conditions within a cell or organism despite external changes.

c) Keeping a constant pH inside a cell or organism despite external changes.

d) Keeping constant conditions outside a cell or organism despite internal changes.

3. The two most abundant molecules in the plasma membrane are:

1.

2.

4. This is true of the structure of the plasma membrane:

a) It is a double layer of protein molecules with phospholipid molecules randomly dotted through it

b) It is single layer of phospholipid molecules

c) It is a double layer of phospholipid molecules with protein molecules dotted in it.

d) It is single layer of protein molecules with phospholipids dotted in it.

5. Add the following labels to the diagram of the plasma membrane shown below. protein molecules; protein channel; double layer of phospholipid molecules

1. What is the difference between permeable, impermeable, and selectively permeable membranes?

C Permeable: Permitting passage of materials.

C Impermeable: Not permitting passage of materials.

C Selectively permeable: Allowing passage of some materials, but not others.

2. The movement of molecules from an area of ______to an area of lower concentration is called ______.

3. Explain how diffusion helps move substances into and out of cells.

4. The diffusion of water through a ______membrane is called ______. Water moves from an area of ______concentration to an area of ______concentration.

5. What happens to the size and shape of a cell if the concentration of solute molecules outside the cell is greater than the concentration of solute molecules inside the cell? What might be the result?

6. Below is a diagram of red blood cells surrounded by IV fluid. How many solvent molecules are in the red blood cell? ______

How many solute molecules are in the IV fluid? ______

The membrane is permeable to water only, which direction will water flow (if at all)? ______

Is the IV fluid hypotonic, hypertonic, or isotonic? ______