Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH8.1 Active Reading
Section: Cell Membrane
Read the passage below. Then answer the questions that follow.
A cell membrane is made of a double layer of phospholipid
molecules. Each layer is a mirror image of the other layer. The
structure is called a lipid bilayer.
Located within the lipid bilayer of the cell membrane are
proteins of different types. Each type of membrane protein plays a
vital role in the life of a cell. Cell-surface markers are membrane
proteins that are attached to a carbohydrate on the cell’s surface.
Together, the protein and carbohydrate help other cells recognize
the cell type—liver cell or heart cell, for example. Receptor
proteins are membrane proteins that recognize and bind to specific
substances outside the cell. When this happens, the inside of the
cell changes, as well. In this way, receptor proteins help cells
detect and change in response to things in the environment outside
the cell. Enzymes are proteins that change the rate of chemical
reactions. Various enzymes in the cell membrane are involved in
important biochemical reactions inside the cell. Many substances
needed inside the cell cannot pass through the cell membrane on
their own. Transport proteins are membrane proteins that aid the
movement of these substances through the lipid bilayer of the cell
membrane. In this way, transport proteins help carry a variety of
substances into and out of the cell.
SKILL: USING CONTEXT CLUES
Read each question, and write your answer in the space provided.
1. The prefix bi- means “two.” Why is the term lipid bilayer a good name for a
cell membrane?
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2. Why are the proteins described in the second paragraph classified together in a
group referred to as membrane proteins?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Cells and Their Environment
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
SKILL: ORGANIZING INFORMATION
The second paragraph of this passage identifies four different types of proteins
found in the cell membrane. Complete the table below by listing each type of
protein and its function in the spaces provided.
Type of protein
Function
3.
4.
5.
6.
7.
8.
9.
10.
In the space provided, write the letter of the response that best answers the
question.
_____ 11. Would you expect a skin cell to have different cell-surface markers
than a muscle cell?
a. No; all cells need to mark their outer surfaces.
b. Yes; each different type of cell might need to signal other cells in
different ways.
c. No; all cells have an outer membrane formed of a lipid bilayer.
d. Yes; the cell-surface markers would be different because the cells
are of different types.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
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Cells and Their Environment
Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH8.2 Active Reading
Section: Cell Transport
Read the passage below. Notice that the sentences are numbered. Then answer
the questions that follow.
1
The diffusion of water through a selectively permeable
membrane is called osmosis. 2 Like other forms of diffusion,
osmosis involves the movement of a substance—water—down its
concentration gradient. 3 Osmosis is a type of passive transport.
4
If the solutions on either side of the cell membrane have
different concentrations of dissolved particles, they will also have
different concentrations of free water molecules. 5 That is because
some of the dissolved particles, which are ions or polar substances,
will bind with some of the water molecules. 6 Osmosis will occur
as water molecules diffuse into the solution with the lower
concentration of free water molecules.
7
Water molecules cannot move directly across the cell
membrane. 8 That is because they are polar and repelled by the
nonpolar interior of the cell membrane. 9 Water crosses the cell
membrane by facilitated diffusion. 10 The cell membrane has
channel proteins for water. 11 These channel proteins let only water
molecules through.
SKILL: READING EFFECTIVELY
Read each question, and write your answer in the space provided.
1. What Key Term is defined in this passage? What does this term mean?
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2. How are diffusion and osmosis related?
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3. What does the word water in Sentence 2 tell you about osmosis?
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4. What happens to the concentration of free water molecules when a substance
dissolves in the water?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cells and Their Environment
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
5. Which sentence explains why dissolving substances affects water
concentration? Summarize the reason in your own words.
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6. Why can’t water move freely across a cell membrane? Which sentence gives
the explanation for this?
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7. What facilitates the diffusion of water across the cell membrane?
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In the space provided, write the letter of the response that best answers the
question.
_____ 8. What happens when a substance dissolves in the watery solution
outside of a cell and equilibrium is disrupted?
a. Water from the cell will move into the solution.
b. Water from the solution will move into the cell.
c. The pores in the cell membrane will become clogged with the
dissolved substance.
d. Nothing will happen until equilibrium is reestablished.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cells and Their Environment
Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
CH8.3 Active Reading
Section: Cell Communication
Read the passage below. Then answer the questions that follow.
Cell communication occurs when a special molecule called a
signal binds to a specific protein in a cell membrane called a
receptor protein. The binding of the signal and the receptor
protein triggers changes in the cell. This event generally causes
one of the following three types of changes.
A change in the ability of the cell membrane to allow
substances to pass through  This is called a change in the
permeability of the cell membrane. It occurs because the signal
causes one or more types of transport proteins either to open or to
close.
The activation of enzymes involved in one or more chemical
reactions vital to the cell  Enzymes change the rate at which
reactions take place. They make chemical reactions in the cell go
fast enough to sustain life. Many enzymes are proteins. Enzyme
activation can occur if a signal molecule binds with a receptor
protein that also is an enzyme. The binding of the signal with the
enzyme can activate the enzyme.
The release of a second messenger inside the cell  In this case,
the binding of the signal and the receptor protein causes a second
signal molecule to be released inside the cell. The second signal is
the second messenger. It can cause many types of changes inside
the cell. It can activate enzymes, cause changes in the cytoplasm,
or cause changes in the nucleus.
SKILL: RECOGNIZING CAUSE AND EFFECT
Read each question, and write your answer in the space provided.
1. What event is the basis for cell communication?
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2. Explain how cell communication can cause a change in the permeability of a
cell membrane.
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cells and Their Environment
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
3. What do enzymes do?
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4. Explain how cell communication can cause enzymes in a cell to become
activated.
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5. What is a second messenger, and what causes a second messenger to be sent?
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6. What kinds of changes in a cell do second messengers usually cause?
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In the space provided, write the letter of the phrase that best answers the question.
_____ 7. What is permeability?
a. the activation of an enzyme
b. the binding of a signal to a receptor protein
c. the ability of a membrane to allow substances to pass through it
d. All of the above
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
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Cells and Their Environment