1.Which of the following are found only in plant cells?
- gap junctions
- desmosomes
- plasmodesmata
- tight junctions
2. The principal force driving movement in diffusion is the __________.
- temperature
- particle size
- concentration gradient
- membrane surface area
3. What problem is faced by organisms that live in fresh water?
- Their bodies tend to take in too much water.
- They have no way of controlling their tonicity.
- Only salt water poses problems for animals that live in it.
- Their bodies tend to lose too much water to their environment.
4. The key components of desmosomes are cadherins and __________.
- actin
- microfilaments
- intermediate filaments
- microtubules
5. How does the structure of a plasmodesma differ from that of a gap junction?
6. Explain how the extracellular matrix functions.
7. Discuss why the following affect the rate of diffusion: molecular size, temperature, solution density, and the distance that must be traveled.
8. Why does water move through a membrane?
9. Which plasma membrane component can be either found on its surface or embedded in the membrane structure?
- protein
- cholesterol
- carbohydrate
- phospholipid
10. What is the primary function of carbohydrates attached to the exterior of cell membranes?
- identification of the cell
- flexibility of the membrane
- strengthening the membrane
- channels through membrane