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Chapter 4.2 Cell Membrane (pages 73-75 ModernBio)
Keystone Standards:
A.4.1.1 Describe how the structure of the plasma membrane allows it too function as a regulatory structure and
protective barrier for a cell.
A.4.1.2. Compare the mechanisms that transport materials across the cell membrane
1. Name two functions of the cell membrane:
___________________________________________________________________
2. The cell membrane contains ____________________molecules that are embedded in the lipid bilayer.
3. Some substances can easily cross while other substances cannot cross the cell membrane. This is
called___________________ _____________________.
4. The lipid bilayer is composed of “hydrophilic heads,” and “hydrophobic tails”.
What does hydro mean (not in this section of the book)? ______________
What does phobic mean?
__________________________
What does philic mean (think Philly, the city of brotherly _________)?
5. Define them by putting the two meanings together:
_________
Hydrophobic
Hydrophilic
6. Why do scientists call the membrane a “mosaic”? _______________________________________
7. On the image, label the
a. lipid bilayer
a1. hydrophobic tail
a2. hydrophilic head
b. protein channel
c. carbohydrate chains
Chapter 5.1 Passive Transport (pg 95/96)
8. When the concentration of molecules is the same throughout a space it has reached a state of
___________________.
9. The cell membrane will allow certain molecules to pass through the membrane. The molecules move
across the membrane from areas of _____________ _______________ to areas of ______________
____________ on the other side.
10. Define diffusion: ______________________________________________________________
_______________________________________________________________
11. Diffusion depends on ____________________ particle movements, therefore it [ does | does not ]
(circle) require energy.
OSMOSIS (pg 96/99)
12. Osmosis does not require energy therefore it is called _______________ transport.
13. Define osmosis: _________________________________________________________
14. Isotonic means _____________________________
Hypertonic means ___________________________
Hypotonic means ____________________________
15. Because cells are hypertonic in relation to fresh water (the water would be considered hypotonic),
water will move ___________ of the cell. If that happens, the cell will become ____________________
and can even burst.
16. In plant and bacteria cells, what keeps them from bursting due to osmotic pressure? ___________
17. What happens to a plant when plasmolysis occurs?
FACILITATED DIFFUSION (pg 99-100)
18. Cell membranes have _________________________ that make it easy for certain molecules to
cross the membrane.
19. When proteins help molecules move across the membrane, it is called
_________________________________________________
20. A good example of facilitated diffusion is glucose. Explain two important properties of facilitated
diffusion.
ACTIVE TRANSPORT Ch 5.2 (pg 101-104)
21. Active transport moves molecules [ with | against ] the concentration gradient.
22. Active transport requires _____________________________
23. What molecules supplies the energy for active transport? _________________
24. Changes in protein shape seem to play an important role in the ______________ process.
25. What is the purpose of the Na+K+ pump (sodium potassium)? Briefly explain how this process
works? What type of cell uses it?
26. Define endocytosis: _______________________________________________________
27. What are the two types of endocytosis?
28. Cells release large amounts of material in a process called _________________________
TEST YOURSELF
1. Which of the following is NOT an example of active transport?
a. facilitated diffusion
b. osmosis
c. endocytosis
d. both a & b
2. Which process always involves the movement of materials from inside the cell to outside the
cell? a. osmosis
b. exocytosis
c. phagocytosis
d. pinocytosis
3. Cell membranes are constructed mainly from:
a. lipid bilayers
b. carbohydrate gates
c. protein pumps
d. free moving proteins
4. A substance that moves across a cell membrane without using the cell’s energy tends to
move:
a. away from the area of equilibrium
b. away from the area where it is less concentrated
c. away from the area where it is more concentrated
d. toward the middle of the cell
5. The movement of water across a selectively permeable membrane is called:
a. exocytosis
b. endocytosis
c. phagocytosis
d. osmosis