Name _________________________ Class ______ Date _________
TEKS 7.12D Differentiate between structure and function in plant and animal cell organelles,
including cell membrane, cell wall, nucleus, cytoplasm, mitochondrion, chloroplast, and vacuole.
TEKS 7.12E Compare the functions of a cell to the functions of organisms such as waste removal.
Looking Inside Cells
Cells are too small to see without a microscope. When you look
at a cell through a microscope, you can usually see the outer
edge of the cell. Sometimes you can also see smaller structures
within the cell. Each kind of cell structure has a different
function within its cell.
Organelles In the picture, you can see many
of the tiny cell structures inside a cell. These structures are
called organelles. Each organelle carries out specific functions
within its cell. In this lesson, you will read about the structures
that plant and animal cells have in common. You will also read
about some differences between plant and animal cells.
What makes up the outside of a cell?
Cell Wall The cell wall is a rigid layer that surrounds the cells
of plants and some other organisms. The cells of animals, in
contrast, do not have cell walls. A plant’s cell wall helps protect and support the cell. The cell wall is made
mostly of a strong material called cellulose. Still, many materials, including water and oxygen, can pass
through the cell wall easily.
Cell Membrane Think about how a window screen allows air to enter and leave a room but keeps
insects out. One of the functions of the cell membrane is something like that of a screen. The cell
membrane controls what substances pass into and out of a cell. Everything a cell needs, such as food
particles, water, and oxygen, enters through the cell membrane. Waste products leave the same way. In
addition, the cell membrane prevents harmful materials from entering the cell. Figure 1 above shows an
animal cell, with the cell membrane around it.
All cells have cell membranes. In plant cells, the cell membrane is just inside the cell wall. In cells without
cell walls, the cell membrane forms the border between the cell and its environment.
What is the nucleus?
A cell doesn’t have a brain, but it has something that
functions in a similar way.
A large oval structure called the nucleus (NOO klee us)
acts as a cell’s control center, directing all of the cell’s
activities. The nucleus is the largest of the cell’s organelles.
Notice in Figure 2 that the nucleus is surrounded by a
membrane, called the nuclear envelope. Materials pass in
and out of the nucleus through pores in the nuclear
envelope.
Chromatin and Ribosomes You may wonder how the
nucleus “knows” how to direct the cell. Chromatin, thin
strands of material that fill the nucleus, contains
information for directing a cell’s functions. For example, the instructions in the chromatin ensure that leaf
cells grow and divide to form more leaf cells. Notice the small, round structure in the nucleus. This
structure, the nucleolus, is where ribosomes
(RY buh zohmz) are made. Ribosomes are small grain-shaped organelles that produce proteins. Proteins
are important substances in cells.
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Name _________________________ Class ______ Date _________
What is in the cytoplasm?
Cytoplasm Most of a cell consists of a
thick, clear, gel-like fluid. This
cytoplasm fills the region between the
cell membrane and the nucleus. The
fluid of the cytoplasm moves constantly
within a cell, carrying along the nucleus
and other organelles that have specific
jobs.
Mitochondria Floating in the
cytoplasm are rod-shaped structures
that are nicknamed the “powerhouses”
of a cell. You can see them in Figure 3 –
Animal Cell. Mitochondria (myt oh
KAHN dree uh; singular: mitochondrion)
convert energy stored in food to energy the cell can use to live and function.
Vacuoles Plant cells often have one or more large, water-filled sacs floating in the cytoplasm. This type
of sac, called a vacuole (VAK yoo ohl), stores water, food, or other materials needed by the cell. Vacuoles
can also store waste products until the wastes are removed. Some animal cells do not have vacuoles.
Chloroplasts A typical plant cell contains green
structures—called chloroplasts—in the
cytoplasm. A chloroplast captures energy from
sunlight and changes it to a form of energy that
cells can use in making food. Animal cells don’t
have chloroplasts, but the cells of plants and
some other organisms do. Chloroplasts make
leaves green because leaf cells contain many
chloroplasts. Figure 4. Plant Cell
Do Cells Function Like
Organisms?
You have read about the functions of cells. Those
functions may have sounded familiar. Cells are
living things, and they carry out many of the
same life processes as complex organisms. Just as
your body is protected by your skin, a cell has a cell membrane to control which substances pass in and
out of it. You need to eat and drink to live. Animal cells take in food particles through their cell
membranes, and plant cells produce food through a chemical reaction to sunlight. Water passes through
the cell membranes of both plants and animals.
After you eat, your body changes the food into a form that it can use for energy. In a cell, the organelles
convert the energy stored in food to energy the cell can use to live and function. You have to breathe—or
exchange gases—to live, and so does a cell. Oxygen and carbon dioxide pass easily through the cell wall
and cell membrane. Cells also eliminate waste products, just as humans do. Those waste products pass
out of the cell through the cell membrane. Cells are the basic units of structure and function in living
things, and their structures let them meet all their basic life needs.
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Name _________________________ Class ______ Date _________
Cell Organelle Structure and Function
1.Differentiate How are the outsides of plant and animal cells different in their structure and function,
and how are they the same?
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2.Differentiate Name an organelle that all plant cells have but only some animal cells have. Explain what
the organelle does.
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3.Compare Compare the vacuoles in the plant cell shown above and the animal cell shown on the
previous page. Explain how they are the same and different.
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4.Compare Cell Functions to Organism Functions Plant cells produce their own food using sunlight.
What does an animal do that serves a similar function?
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Lesson Check
1.Differentiate For each cell function listed in the chart below, write in the name of the matching
structure. If the particular structure is not found in a cell, write “none.”
Function
Structure in Animal Cells
Structure in Plant Cells
a. controls substances passing
into and out of the cell
b. rigidly protects and
supports the cell
c. directs all of the cell’s
activities
d. fills the cell with fluid and
holds the organelles
e. converts food energy to
energy the cell can use
f. captures energy from
sunlight for the cell to make
food
g. stores water, food, and
other materials
2.Compare Compare how a human cell exchanges oxygen and carbon dioxide with how the human as an
organism does so.
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Name _________________________ Class ______ Date _________
3.Differentiate How are the structure and function of cytoplasm different from those of mitochondria?
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4.Differentiate How do plant and animal organelle structures differ with respect to the function of
obtaining food?
A Animals have a nucleus.
B Animals have cytoplasm.
C Plants have vacuoles.
D Plants have chloroplasts.
TEKS Review
1.Differentiate For each structure listed below, record the function of that cell part and identify
whether it is found in plants, animals, or both plants and animals.
Structure
Function
Plant, Animal, or Both
a. cytoplasm
b. chloroplast
c. cell membrane
d. nucleus
e. vacuole
f. cell wall
g. mitochondrion
2.Compare Complete the analogy.
Bark is to tree as ________________________ is to plant cell.
3.Compare Consider the functions of an animal cell’s nucleus. Compare how it functions like an animal’s
brain.
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4.Contrast Describe the difference in structure and function between how plant and animal cells obtain
food.
a. plant cells ______________________________________________________________________________________
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b. animal cells ____________________________________________________________________________________
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5.Distinguish Describe the structure and function of the nucleus and of a mitochondrion. How is the
functioning of the nucleus dependent on mitochondria?
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