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Membrane Structure Review
1. (3 pts) Give 3 functions of the plasma membrane.
a. contain cell contents
b. shape and support
c. allows materials to enter and exit
2. What is meant by the term “selectively permeable”?
Allows some things to pass and not others
3. (6 pts) Label the plasma membrane (phospholipids, cholesterol, peripheral proteins, integral
proteins, cholesterol, carbohydrate chains)
4.
5.(2 pts) The head of the phospholipid is hydro_phyllic__ and the tail of the phospholipid is
hydro_phobic__.
6. Hydrophilic means water loving, Hydrophobic means water fearing.
7. The fluid mosaic model describes the arrangement of molecules in the cell membrane. This means
that the cell membrane is composed of many individual parts that are constantly flowing or moving
around each other
8. Simple diffusion_ requires NO energy to move things across the cell membrane.
9. With diffusion, molecules move from an area of high concentration to an area of low concentration.
10. Osmosis is the diffusion of water molecules across a cell membrane.
11. (2 pts) Passive transport does not require additional energy & moves materials from high to
concentration.
low
12. (2 pts) Facilitated diffusion uses transport proteins and protein channels to help move materials from high
to low concentrations.
13. Active transport requires additional energy to move materials.
14. Active transport moves materials AGAINST the concentration gradient or from low to
concentration.
high
15. The sodium-potassium pump is an example of active transport.
16. Moving very large particles out of the cell is called exocytosis.
17. In exocytosis, wastes are moved out of the cell in vesicles that fuse with the cell membrane.
18. Endocytosis involves moving large particles into the cell.
19. Passive transport moves molecules down the concentration gradient, while active transport moves
molecules against the concentration gradient.
20. Cells shrink in hypertonic solutions because there is a high concentration of water inside the cell, so water
moves out.
21. Cells swell in hypotonic solutions, because there is a high concentration of water outside of the cell, so
water moves in.
22. In isotonic solutions, concentrations of water inside and outside the cell are equal.
23. (6 pts) Label each beaker solution as isotonic, hypertonic, or hypotonic and draw an arrow to show the direction of
water movement by osmosis. (Solutes cannot move.)
1st beaker: Hypotonic, arrow should be pointing into the cell
2nd beaker: Hypertonic, arrow should be pointing out of the cell
3rd beaker: Isotonic, one arrow going in, one arrow going out
Extra credit: List the functions of proteins in the cell membrane. On your test, you will get one point for
every function you can list.
1.
2.
3.
4.
5.
6.
Cell to Cell recognition
Integrins
Intercellular junctions
Enzymes
Signal Transduction Protein
Transport Proteins