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Directed Reading Section 8.1 - Cell Membrane
Read each question, and write your answer in the space provided.
1. What is homeostasis, and what is the main way that the cell membrane helps maintain homeostasis?
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2. List three other functions of the cell membrane.
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Complete each statement by writing the correct term or phrase in the space provided.
3. The ______________________ ______________________ is made of a double layer of phospholipids. The double
layer of phospholipids is called a(n) ______________________ ______________________.
4. The lipid bilayer forms because there is ______________________ both inside and ______________________ of
the cell.
5. The phosphate ______________________ of a phospholipid is polar. It is ______________________
______________________ water.
6. The long fatty acid ______________________ of a phospholipid are nonpolar. They are ______________________
______________________ water.
7. The lipid bilayer forms a barrier, preventing most molecules from passing through it. Only molecules that are
______________________ in size and ______________________ can pass through the lipid bilayer.
8. Ions, which are ______________________ particles, and ______________________ molecules are repelled by the
nonpolar interior of the lipid bilayer.
9. The cell membrane includes various kinds of ______________________. Some face the inside of the cell. Some
face the ______________________ of the cell. Others span the entire width of the ______________________
______________________.
Read each question, and write your answer in the space provided.
10. What are proteins made of? ________________________________________
11. Why do proteins stay within the lipid bilayer of the cell membrane?
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12. List the four types of proteins found in a cell membrane.
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In the space provided, write the letter of the description that best matches each term.
_____13. cell-surface marker
_____14. receptor protein
_____15. enzyme
_____16. transport protein
a. helps with chemical reactions inside
the cell
b. recognizes and binds to substances
outside the cell, enabling the cell to
sense its environment
c. helps substances move across the
cell membrane
d. identifies the cell type
Directed Reading Section 8.2 - Cell Transport
Read each question, and write your answer in the space provided.
1. What is the purpose of cell transport? What is the difference between active transport and passive transport?
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2. What is equilibrium?
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3. What is diffusion? Why is diffusion an example of passive transport?
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In the space provided, write the letter of the description that best matches each term .
_____ 4. simple diffusion
_____ 5. facilitated diffusion with channel proteins
_____ 6. facilitated diffusion with carrier proteins
a. a substance binds to a protein, which changes shape; both
move together across the cell membrane, where the
substance is released
b. small, nonpolar molecules passing directly through the cell
membrane
c. an ion, sugar, or amino acid moving through a specific pore,
based on the size and charge of the moving substance
Read each question, and write your answer in the space provided.
7. What is osmosis, and why is it important in cells?
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8. Explain how water moves across a cell membrane.
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Match the condition on the right with the numbered action on the left.
_____ 9. water moves into the cell
_____10. a state of ongoing equilibrium occurs
_____11. water moves out of the cell
a. The solution a cell is in is hypertonic, meaning that it has a higher
solute. concentration than the cytoplasm does
b. The solution a cell is in is isotonic, meaning that it has the same solute.
concentration as the cytoplasm does
c. The solution a cell is in is hypotonic, meaning that it has a lower solute
concentration than the cytoplasm does.
Complete each statement by writing the correct term or phrase in the space provided.
12. The transport of a substance across the cell membrane against its concentration gradient is called
______________________ ______________________.
13. The energy needed for active transport is usually supplied by _____________.
Read each question, and write your answer in the space provided.
14. What is the sodium-potassium pump? Describe how it works.
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15. Explain why proteins and polysaccharides cannot be transported across a cell membrane by carrier proteins. How
do these substances cross the cell membrane?
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16. What is endocytosis? Describe how it works.
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17. What is exocytosis? Describe how it works.
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18. What are some circumstances in which cells use exocytosis?
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Directed Reading Section 8.3 - Cell Communication
Read each question, and write your answer in the space provided.
1. What is the main way cells communicate and coordinate activities?
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2. What is a target cell?
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3. How might neighboring cells communicate?
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4. What is an environmental signal? Give an example.
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5. Cells are constantly bombarded by signals. How are they able to respond to only the few signals important to their
cell function?
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6. What is a binding site, and why does it have a specific shape?
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7. Summarize the three responses cells generally have to a specific signal.
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In the space provided, write the letter of the description that best matches each term.
_____ 8. signal
_____ 9. receptor protein
_____10. enzyme
_____11. second messenger
a. forms in response to information from outside a cell and acts as an
information carrier within a cell, causing changes in the cytoplasm or the
nucleus
b. binds to a specific signal molecule, causing a cell to respond
c. speeds up a specific chemical reaction in the cell
d. carries information from one cell or cells to other cells