Download Eukaryotic Cells and Cell Organelles

SECTION
3.2
Eukaryotic Cells and
Cell Organelles
Student
text pages
;ADG>96HI6C96G9H
73–79
SC.912.L.14.3
KEY CONCEPT Eukaryotic cells share many similarities.
Cells have an internal structure.
Your skeleton is made of bones that help keep all your body parts in
place. Eukaryotic cells have a skeleton, too. It is called the cytoskeleton.
The cytoskeleton is a network of protein fibers. They look like a lot of
tiny strings that crisscross a cell. The cytoskeleton is the framework of a
cell. It gives a cell shape, support, and strength. The cytoskeleton can
cytoskeleton
change as a cell needs to change.
What might a cell look like if it had no cytoskeleton?
The cytoskeleton
supports and shapes
the cell.
Several organelles are involved in making and
processing proteins.
Proteins are a very important type of molecule that are used in all life
functions. Basic life functions include reproduction, repair, and growth
of injured cells or body parts. Life functions also include the regulation
of circulation and digestion systems. You need proteins to digest the
foods you eat or to move your muscles when you ride a bike. Proteins
are at work when your heart beats or your eye blinks. Some hormones
such as insulin, which controls your blood sugar levels, are also proteins.
Proteins are very important, and many organelles work together
to make them. These organelles include the nucleus, endoplasmic
reticulum, ribosomes, the Golgi apparatus, and vesicles. Ribosomes
are found in both eukaryotic and prokaryotic cells. However, the other
organelles—those surrounded by a membrane—are found only in
eukaryotic cells.
Nucleus The nucleus stores and protects the DNA of the cell. DNA
contains the genes that are the instructions for making proteins.
Endoplasmic Reticulum (ER) The endoplasmic reticulum (ER) is a
network of thin, folded membranes that helps in the production of
proteins and other molecules. The membranes are like a maze; they fold
back on themselves and have little spaces inside the folds. There are two
types of ER, smooth and rough. The rough ER looks bumpy because it
has ribosomes attached to it.
The nucleus stores
and protects DNA.
Visual Connection
See pictures in student
text, pgs. 75–79
Interactive Reader
39
Ribosomes Ribosomes are tiny organelles that link amino acids
together to form proteins. They are found on the surface of the ER and
floating freely in the cytoplasm.
Golgi apparatus Each Golgi apparatus is a stack of layers of membranes. In the Golgi apparatus, proteins are changed, put into packages,
and carried to other places in the cell.
Vesicles Vesicles are small sacs. They carry different molecules to where
they are needed. Vesicles are generally short-lived and are formed and
recycled as needed.
What
of the nucleus?
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What is the
jobisofthe
thejob
nucleus?
The Golgi apparatus
modifies, packages, and
transports proteins.
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Other organelles have various functions.
Some organelles do jobs other than making proteins.
Mitochondria Mitochondria are bean-shaped organelles that produce
chemical energy that is usable by a cell. They have two membranes.
The inner membrane has lots of folds that form compartments. Mitochondria also have their own ribosomes and DNA. At one time, mitochondria may have been independent prokaryotes that were taken in by
larger cells.
Vacuoles Vacuoles are sacs of fluids that store materials in a cell. These
materials include water, food molecules, ions, and enzymes. Many plant
cells have a large central vacuole. When filled with fluid, the central
vacuole exerts pressure that can help support the plant.
Lysosomes Lysosomes are organelles that contain enzymes. They
protect a cell by attacking incoming bacteria or viruses. They also break
down old cell parts.
Centrioles Centrioles are shaped like cylinders. They are made of tiny
tubes in a circle. They move when animal cells divide in two. Centrioles
help form cilia and flagella, structures that help cells to move or to move
liquids past a cell. Centrioles are surrounded by the centrosome. The
centrosome is a small region of cytoplasm that organizes proteins into
fibers that help cells divide.
Highlight the organelle that produces usable energy for a cell.
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McDougal Littell Biology
Mitochondria generate
usable energy for the
cell.
Centrioles are separated
during cell division.
They help form cilia
and flagella.
SUMMARY OF CELL STRUCTURE
Eukaryotic cells have highly organized structures, including membrane-bound
organelles. Plant and animal cells share many of the same types of organelles,
but both also have organelles that are unique to their needs.
PLANT CELL
FOUND IN PLANT CELLS
FOUND IN BOTH
chloroplast
cytoskeleton
central vacuole
vesicle
cell wall
nucleus
nucleolus
endoplasmic reticulum (rough)
ribosome
centrosome
endoplasmic reticulum (smooth)
cell membrane
Golgi apparatus
mitochondrion
vacuole
ANIMAL CELL
FOUND IN ANIMAL CELLS
centriole
lysosome
cytoskeleton
vesicle
nucleus
nucleolus
endoplasmic reticulum (rough)
ribosome
centrosome
endoplasmic reticulum (smooth)
cell membrane
Golgi apparatus
mitochondrion
vacuole
Interactive Reader
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Plant cells have cell walls and chloroplasts.
Plant cells have two parts that animal cells do not have. Plant cells have
cell walls and chloroplasts.
Cell walls The cell wall is a strong, rigid layer that protects, supports,
and shapes the plant cell. It surrounds the cell membrane. Some cell
walls are very thick, such as those in a tree. When joined with others,
they can support a very large plant. Some cell walls are thinner, like
those in celery.
Chloroplasts Chloroplasts carry out photosynthesis that stores energy
from sunlight as chemical energy for the plant. The chloro- part of the
name chloroplast means “green.” Chloroplasts contain chlorophyll,
a green pigment, that helps capture energy from sunlight. Like mitochondria, chloroplasts have two membranes and their own ribosomes
and DNA.
Circle the organelle that is similar in structure to mitochondria.
3.2
Mark It Up
Vocabulary Check
cytoskeleton
nucleus
endoplasmic reticulum
ribosome
Golgi apparatus
vesicle
mitochondrion
vacuole
lysosome
centriole
cell wall
chloroplast
Go back and highlight
each sentence that
has a vocabulary
word in bold.
Choose the correct term from the list for each description.
1. little sacs that carry molecules
2. bumps that link amino acids
3. green organelles for photosynthesis
4. the skeleton of the cell
5. bean-shaped energy supplier
6. holder and protector of DNA
3.2
The Big Picture
7. What do the nucleus, ER, ribosomes, Golgi apparatus, and vesicles
work together to do?
8. How are plant cells different from animals cells?
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McDougal Littell Biology
Chloroplasts convert
solar energy into chemical energy through
photosynthesis.