Cellular Structure and Function
Reading Essentials Chapter 7 Cellular Structure and Function
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Read to Learn
Cytoplasm and Cytoskeleton
The environment inside the plasma membrane is a
semifl uid material called cytoplasm. Scientists once thought
the organelles of eukaryotic cells fl oated freely in the cell’s
cytoplasm. As technology improved, scientists discovered
more about cell structures. They discovered a structure within
the cytoplasm called the cytoskeleton. The cytoskeleton is a
network of long, thin protein fi bers that provide an anchor
for organelles inside the cell. The cell’s shape and movement
depend on the cytoskeleton.
Two types of protein fi bers make up the cytoskeleton.
Microtubules are long, hollow protein cylinders that form a
rm skeleton for the cell. They assist in moving substances
within the cell. Microfi laments are thin protein threads that
help give the cell shape and enable the entire cell or parts of
the cell to move.
Cell Structures
All chemical processes of a typical eukaryotic cell take place
in the organelles, which move around in the cell’s cytoplasm.
Proteins are produced, food is transformed into energy, and
wastes are processed in the organelles. Each organelle has a
unique structure and function.
section Structures and Organelles
Before You Read
For cells to function correctly, each part must do its job.
Members of families have jobs or chores that help the whole
family. On the lines below, list your family members and their
1. Name one cell function
that takes place in
Identify the Parts Highlight
each cell structure as you read
about it. Underline the function
of each part.
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The eukaryotic cell contains
What You’ll Learn
differences in the structures of
plant and animal cells
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Chapter 7 Cellular Structure and Function Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How are plant and animal cells different?
The fi gure below shows a typical plant cell and a typical
animal cell. Note how many organelles are found in both types
of cells. Also, note a few differences, such as the chloroplast
that appears only in the plant cell. Observe that the vacuole
in the plant cell is much larger than the vacuole in the animal
Picture This
2. Highlight the names of
structures found in both
plant cells and animal
cells. Circle the names of
structures that are found
only in plant cells. Underline
the names of structures that
are found only in animal
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Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What structure manages cell processes?
The nucleus is the cell’s managing structure. Most of the
cell’s genetic material (DNA) is in the nucleus. DNA defi nes
the cell and controls protein production. A nuclear envelope
surrounds the nucleus. Substances pass through the nuclear
envelope to move in and out of the nucleus.
Which organelle produces proteins?
Ribosomes produce proteins and are made of two
components—RNA and protein. Ribosomes are produced in
the nucleolus, a structure located inside the nucleus. Some
ribosomes fl oat freely in the cytoplasm. They produce proteins
that will be used by other cells. Other ribosomes attach to an
organelle called the endoplasmic reticulum.
What attaches to rough endoplasmic reticulum?
The endoplasmic reticulum, (en duh PLAZ mihk •
rih TIHK yuh lum) also called ER, is a membrane system of
folded sacs and channels to which ribosomes are attached.
There are two types of ER. The fi rst type is called rough
endoplasmic reticulum. This is the area where ribosomes
attach to the ERs surface. The ribosomes appear to create
bumps or rough places on the membrane. The second type,
smooth endoplasmic reticulum, has no ribosomes attached.
Smooth ER produces complex carbohydrates and lipids.
What is the purpose of the Golgi apparatus?
Once proteins are created, they move to another organelle,
the Golgi (GAWL jee) apparatus. The Golgi apparatus
modifi es, sorts, and packs the proteins into sacs called vesicles.
The vesicles fuse with the cell’s plasma membrane. There the
vesicles release the proteins, which move through the plasma
membrane to the environment outside the cell.
What is stored in vacuoles?
Cells have vesicles called vacuoles that act as temporary
storage for materials in the cytoplasm. Vacuoles can store
food and other material needed by a cell. They can also store
wastes. Plant cells normally have one large vacuole. Animal
cells might or might not have a few small vacuoles.
What are lysosomes?
Lysosomes are vesicles that contain substances that digest
excess or worn-out organelles and food particles. Lysosomes
also digest bacteria and viruses that enter the cell.
3. Explain What is the role
of DNA?
Reading Essentials Chapter 7 Cellular Structure and Function
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Chapter 7 Cellular Structure and Function Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What makes up a centriole?
Centrioles are organelles made of microtubules that
function during cell division. They usually are found near the
nucleus of the cell. Plant cells do not contain centrioles.
Which organelle produces energy?
Cells need energy to survive. The organelles that convert
fuel particles such as sugars into usable energy are called
mitochondria (mi tuh KAHN dree uh). A mitochondrion has
an outer membrane and an inner membrane with many folds,
as shown in the fi gure below. The membrane provides a large
surface area for breaking the bonds of sugar molecules. Energy is
produced when the bonds are broken.
How do plant and animal cells differ?
In addition to mitochondria, plant cells contain chloroplasts.
Chloroplasts are organelles that capture light energy and
convert it to chemical energy through a process called
photosynthesis. Plants can use light energy from any light
source—usually the Sun. Animal cells do not have chloroplasts
and cannot use solar energy as fuel for cell processes.
Plants also have cell walls. The cell wall is a mesh of
bers that surrounds the plasma membrane. It protects and
supports the cell. Plant cell walls are made of a carbohydrate
known as cellulose.
What are cilia and fl agella?
Some animal cell surfaces have cilia or fl agella that extend
beyond the plasma membrane. Cilia are short projections
that look like hairs. They move back and forth, similar to
the motion of the oars of a rowboat. Flagella are longer,
whiplike projections that propel cells. Both cilia and fl agella
are composed of microtubules. They move cells through their
watery environments. Cilia also move substances along the
surface of the cell.
Picture This
4. Explain why the inner
membrane has many folds.
5. Recall What is another
function of microtubules?
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Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Comparing Cells
The table below summarizes the structures of eukaryotic
plant and animal cells. The function of each structure is
described. Note that prokaryotic cells lack most of the
organelles found in eukaryotic cells.
Organelles at Work
The structures in the cell work together to perform cell
functions. The synthesis of proteins is a major cell function,
which begins in the nucleus. Protein synthesis continues with
the ribosomes on the rough ER and the ribosomes that fl oat
freely in the cytoplasm. Most proteins made on the rough ER
are sent to the Golgi apparatus. There they are packaged in
vesicles and sent to other organelles or out of the cell. Like each
member of a soccer team, each cell structure has a specifi c task
to do to make the cell function properly.
Cell Structure Function
Present in
Plant/Animal Cells
Cell wall protects and supports plant cells plant cells only
Centriole important in cell division animal cells only
Chloroplast site where photosynthesis occurs plant cells only
Cilia aids in moving the cell and moving substances along the
surface of the cell
some animal cells
Cytoskeleton a framework for the cell within the cytoplasm both
reticulum (ER)
site of protein synthesis; where ribosomes attach both
Flagellum aids in moving and feeding the cell some animal cells
Golgi apparatus modifi es and packages proteins for distribution outside the cell both
Lysosome contains digestive enzymes for substance break down animal cells only
Mitochondrion supplies energy to the rest of the cell both
Nucleus directs the production of proteins and cell division both
Plasma membrane controls the movement of substances in and out of the cell both
Ribosome produces proteins both
Vacuole stores materials temporarily plant cell—one
large; animal
cell—a few small
Picture This
6. Highlight the organelle
to which ribosomes attach.
7. Identify a major cell
Reading Essentials Chapter 7 Cellular Structure and Function
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