Download 7.2 Cell Structure

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7.2 Cell Structure
Lesson Summary
Cell Organization Eukaryotic cells contain a nucleus and many specialized structures.
Cytoplasm is the fluid portion of a cell.
Organelles are structures that have specialized functions in eukaryotic cells.
The nucleus contains DNA and controls the activity of a cell.
Organelles That Store, Clean Up, and Support These structures include:
vacuoles: membrane-enclosed saclike structures that store water, salts, and organic
molecules
lysosomes: small organelles filled with enzymes that break down large molecules and
organelles that are no longer useful
the cytoskeleton: a network of protein filaments; it helps the cell maintain its shape and is
involved in movement
centrioles: organelles made from tubulins; they help organize cell division in animal cells
Organelles That Build Proteins Three kinds of organelles work with the nucleus to
make and distribute proteins:
ribosomes: small particles of RNA and protein found throughout the cytoplasm in all
cells; they produce proteins by following coded instructions from DNA
the endoplasmic reticulum (ER): an internal membrane system where lipid components
of the cell membrane are assembled, along with proteins and other materials
the Golgi apparatus: an organelle that appears as a stack of flattened membranes; it
modifies, sorts, and packages proteins and other materials from the ER for storage in the
cell or release outside the cell
Organelles That Capture and Release Energy Two types of organelles act as
power plants of the cells. Both types are surrounded by two membranes.
Chloroplasts capture the energy from sunlight and convert it into food that contains
chemical energy in a process called photosynthesis. Cells of plants and some other
organisms contain chloroplasts, which contain chlorophyll.
Mitochondria are found in nearly all eukaryotic cells; they convert the chemical energy
stored in food to a usable form.
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Cellular Boundaries All cells are surrounded by a cell membrane. Many cells also have a
cell wall. Both cell membranes and cell walls separate cells from the environment and provide
support.
Cell walls support, shape, and protect the cell. Most prokaryotes and many eukaryotes have
them. Animals do not have cell walls. Cell walls lie outside the cell membrane. Most cell
walls allow materials to pass through them.
A cell membrane consists of a lipid bilayer, a strong but flexible barrier between the cell and
its surroundings. The cell membrane regulates what enters and leaves the cell and also
protects and supports the cell. Most biological membranes are selectively permeable,
allowing some substances, but not others, to pass across them.
Lesson Objectives
Describe the structure and function of the cell nucleus.
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Describe the role of vacuoles, lysosomes, and the cytoskeleton.
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Identify the role of ribosomes, endoplasmic reticulum, and Golgi apparatus in making
proteins.
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Describe the function of the chloroplasts and mitochondria in the cell.
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Describe the function of the cell membrane.
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BUILD Vocabulary
A. The chart below and on the next page shows key words from the lesson with their
definitions.
B.
Term
Definition
Structure around plant cells, fungus cells, and some bacterial cells
that supports and protects
Structure in animal cells that helps organize cell division
Structure in plant cells that captures the sun’s energy and changes
it into chemical energy
Fluid portion of the cell outside the nucleus
Network of protein filaments that gives a cell its shape and
organizes its organelles
Internal membrane system of a cell where proteins are assembled
Series of flattened sacs that prepares proteins and other materials
for export from the cell
Enzyme-filled structure that breaks down complex molecules or
worn-out organelles
Organelle that changes the chemical energy in food into a form that
is easier for the cell to use
Structure within a cell that acts like a specialized organ
Structure that assembles proteins
Saclike structure that stores materials like water and nutrients
BUILD Understanding
Venn Diagram A Venn diagram is made up of overlapping circles. It is a useful tool for
comparing two or even three topics.
Use terms from the box to complete the Venn diagram.
cell membrane
cell wall
centriole
chloroplast
cytoplasm
cytoskeleton
DNA found in cytoplasm
endoplasmic reticulum
Golgi apparatus
lysosome
Prokaryotes
mitochondria
nucleus containing DNA
ribosome
vacuole
Eukaryotes
Both
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Cell Organization
An organelle is a specialized cell structure. Each organelle functions in a different way. All of the
organelles help the cell carry out life processes.
Use the terms in the box to write the name of the organelle underneath its picture.
endoplasmic reticulum
Golgi apparatus
mitochondrion
nucleus
Function
Organelle
Controls most cell processes and stores genetic
material
Where lipid parts of the cell membrane and
proteins for export are assembled and stored
Modifies, sorts, and packages materials from
the endoplasmic reticulum
Converts the energy stored in food into a more
usable form
BUILD Connections
The Cell As a Living Factory An analogy takes two things
that seem to be different and shows how they can be similar.
1. If the cell were a factory, what part would serve as the main
office?
2. Which cell part would provide electricity?
3. With a partner, discuss how the actions of the forklifts are
related to actions in cells.
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Cell Organization
Follow the directions.
1. Use the words below to label the plant cell. Some structures have been labeled for you.
cell wall
chloroplast
mitochondrion
nucleus
ribosome
vacuole
Plant Cell
smooth endoplasmic reticulum
Golgi apparatus
rough endoplasmic reticulum
cell membrane
2. Use the words below to label the animal cell. Some structures have been labeled for you.
cell membrane
Golgi apparatus
mitochondrion
nucleus
rough endoplasmic reticulum
ribosome
Animal Cell
smooth
endoplasmic
reticulum
centrioles
Use the diagrams to answer the questions.
3. Which structure is found in a plant cell but not in an animal cell? Circle the correct answer.
chloroplast
cell membrane
ribosome
4. What is the main function of vacuoles?
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