CHAPTER 4: CELL STRUCTURE
WHERE DOES IT ALL FIT IN?
The information in Chapter 4 provides details about prokaryotic and eukaryotic cells. It puts the
chemistry of the earlier chapters into a picture of the cell. Emphasis is placed on eukaryotic cells
because of their complexity and great diversity. Many terms are introduced in the chapter and show
be reinforced as much as possible during coverage of cell in this and other chapters dealing with cell
concepts. Chapter 5 is a critical reference when covering the chapters later in the text that describe
cell transport, metabolism, cell replication, and genetics.
SYNOPSIS
All life is composed of cells, individually or as components of multicellular organisms. With certain
exceptions, cells are very small. Substances diffuse more rapidly in a small cell, enhancing both its
metabolism and its communication with other cells and with its environment. As a cell’s size
increases, its volume increases at a much greater rate than its surface area. A cell’s survival depends
on its surface, where all molecules enter and exit. If there is too little surface to support the workings
of the interior, the cell will die.
Many of the structural differences between prokaryotes and eukaryotes are visible at the level of the
light microscope; the presence of the nucleus in eukaryotes, for example. The nuclear material in
prokaryotes is a single, circular strand of DNA, unencumbered by either proteins or a surrounding
membrane and is difficult to see at the same scale. Observation with an electron microscope reveals
details about the cytoskeleton and internal membrane systems of the eukaryotes, both absent in
prokaryotes. Different kinds of microscopes and different staining procedures can be used to obtain
a desired image.
On a biochemical level, all of the reactions of a prokaryote, including those associated with
ribosomes, occur openly in its cytoplasm, bounded only by invaginations of the plasma membrane.
The reactions in a eukaryote are compartmentalized by the endoplasmic reticulum (ER) and by
various membrane-bound organelles. Among these organelles are the nucleus, the Golgi apparatus,
lysosomes, and microbodies (peroxisomes and glyoxysomes). The smooth and rough ER differ in
appearance and function.
Rough endoplasmic reticulum possesses ribosomes while smooth endoplasmic reticulum lacks them.
Various chemical products are synthesized on the rough endoplasmic reticulum, channeled into the
Golgi bodies, and packaged into microbodies and lysosomes. Smooth ER contains embedded
enzymes and is involved in carbohydrate and lipid synthesis and detoxification.
Some eukaryotic organelles contain DNA, notable among these are the cell’s powerhouses, the
mitochondria and the chloroplasts. The cytoskeleton, composed of actin filaments, microtubules, and
intermediate filaments, provides a framework to anchor the organelles and give a cell its shape.
Microtubules move organelles within a cell assisted by kinesin and dynein proteins. They also
provide the characteristic 9+2 arrangement of eukaryotic flagella, cilia, and centrioles. Plant, fungi,
and some protists have special adaptations that are lacking in other cells. Plant cells have a large
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central vacuole which serves as a storage compartment and helps increase the cell’s surface-tovolume ratio. Plants cells and some protists have strong, rigid cell walls composed of cellulose
whereas fungi have chitin in their cell walls. Animal cells lack cell walls but have their cytoskeleton
linked to the extracellular matrix.
LEARNING OUTCOMES
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Understand why most cells are small in size.
Describe the function and the composition of the plasma membrane.
Explain the principles of the cell theory.
Differentiate between prokaryotes and eukaryotes.
Understand the importance of the nucleus and its components.
Differentiate between rough and smooth endoplasmic reticulum both in structure and function.
Understand how the endoplasmic reticulum and Golgi apparatus interact with one another and
know with which other organelles they are associated.
Differentiate between the two energy producing organelles of eukaryotes.
Identify the three primary components of the cell’s cytoskeleton and how they affect cell shape,
function, and movement.
Compare and contrast bacterial flagella with eukaryotic flagella and cilia.
Know how plant cells are fundamentally different from other kinds of cells.
Compare the extracellular matrix of animal cells with the cell walls of plants.
COMMON STUDENT MISCONCEPTIONS
There is ample evidence in the educational literature that student misconceptions of information
will inhibit the learning of concepts related to the misinformation. The following concepts
covered in Chapter 4 are commonly the subject of student misconceptions. This information on
“bioliteracy” was collected from faculty and the science education literature.
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Cells are within an organism but do not make up the body
All cells are spherical
Cells are 98% water in chemical composition
The cytoplasm is similar to pure water
All animal cells have every type of organelle
Mitochondria are built by the cell
Mitochondria produced all of the cell’s ATP
Prokaryotes produce ATP in mitochondria
All cells have a nucleus
Plant cells do not have mitochondria
Smooth ER and rough ER are separate structures
The Golgi body is an independent organelle unrelated to the ER
All cells of multicellular organisms carry out the same tasks
Plant cells lack protein whereas animal cells are high in protein
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Cell walls are the same as plasma membranes
Cell membranes are solid
INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE
There is a lot of unfamiliar vocabulary in this chapter. Etymology of new words may be helpful.
Introduce the plasma membrane carefully. The next two chapters delve into its importance
within and between cells.
Most students are familiar with simple cell theory. It may be appropriate to discuss Redi’s and
Pasteur’s experiments refuting spontaneous generation at this point, when discussing cells
originating from other cells. Students have some difficulty with the differences between
prokaryotes and eukaryotes, therefore stress nuclear organization and membrane
compartmentalization as definitive characteristics.
Many texts don’t present much in the way of why cells are the size they are. This is an important
concept elaborated on later in this text, in relation to why most animals and some plants have
specific size limitations.
HIGHER LEVEL ASSESSMENT
Higher level assessment measures a student’s ability to use terms and concepts learned from the
lecture and the textbook. A complete understanding of biology content provides students with
the tools to synthesize new hypotheses and knowledge using the facts they have learned. The
following table provides examples of assessing a student’s ability to apply, analyze, synthesize,
and evaluate information from Chapter 5.
Application
Analysis
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Have students predict which organelles would become more active it the
cell was induced to produce more protein secretions.
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Ask students explain which organelles would be damaged if a drug that
kills prokaryotes were to end a person’s cells.
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Ask students explain a why certain invasive organisms that cause disease
in humans produce chemicals that block in integrins.
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Ask students to explain the implications of a disease that disrupts the
function of the Golgi apparatus.
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Ask students to explain the survival advantages of an infectious agent that
has the ability to disable lysosomes.
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Have students determine some of the consequences of research showing
that nicotine reorganizes cytoskeleton structure.
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Synthesis
Evaluation
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Ask students hypothesize the characteristics of an endosymbiont that
purportedly aids feeding in an organism that has no digestive system.
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Have students determine the best classification of a cell that has
chloroplasts and flagella, but has no cell wall or central vacuole.
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Ask students to explain why some cells in an organism can have 100
times more mitochondria than other cells.
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Ask students to debate the pros and cons of using mechanical devices to
replace lost body functions once carried out by cells.
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Ask students to evaluate the consequences of a health product claiming to
stimulate activity of the mitochondria.
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Have students discuss the benefits and risks of producing agricultural
animals that have chloroplasts expressed in their skin cells.
VISUAL RESOURCES
1. A large, clear plastic bag is a reasonable facsimile of a cell’s plasma membrane. A
prokaryote can be represented by a bag with various objects inside to represent their
metabolic processes. A large bag with the objects inside of smaller bags represents a
eukaryote and its compartmentalizing membrane-bound organelles. One could further
place the bag in a box to represent the cell wall of a plant.
2. Fisher educational division sells a superb yet simple model of a lipid bilayer (and it is
inexpensive). A saturated salt solution is the cell interior, mineral oil the exterior (the oil
floats on the salt solution). Styrofoam balls are one side of the membrane (they float on
the oil), plastic balls are the other side (they stay at the salt/oil interface). Plastic rods or
straws into the balls serve as the lipid tails.
3. One may want to discuss cell fractionation and gradient centrifugation in relationship to
isolating the various cell parts so they can be studied. A short description of various kinds
of microscopes (especially the rationale behind why electron microscopes resolve much
smaller structures) might be helpful, although this is frequently discussed in the
laboratory setting. To a great extent, much of the material in this chapter is supported by
laboratory activities where the students can observe many of the larger structures firsthand.
4. Most students mistakenly associate chloroplasts with plants and mitochondria with only
animals. Stress that mitochondria are present in virtually all eukaryotes. Remember that
these two organelles will be visited again when cell metabolism is discussed. Students
may as well learn their structure now as opposed to later when they will be attempting to
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understand the biochemistry too.
5. Electron micrographs are a must for this material. They can be difficult for students to
interpret, therefore accompanying line drawings that simplify the micrograph are
beneficial. Or use markers to outline and/or colorize particular structures on either
photographs or transparencies.
IN-CLASS CONCEPTUAL DEMONSTRATIONS
A. Organelle Role Playing
Introduction
Critical thinking can be done in many ways to encourage student retention of biology
concepts. Students can be asked to role model different organelles to learn the function of the
organelle and its interconnections with other organelles. This demonstration can be performed in
the classroom or outdoors.
Materials
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Student volunteers to represent one organelle
o Cell membrane
o Nucleus
o Chloroplast
o Mitochondrion
o Rough ER
o Smooth ER
o Golgi apparatus
o Lysosome
Colored markers
8 ½” X 11” sheets of white paper labeled with the name of one organelle
o Cell membrane
o Nucleus
o Chloroplast
o Mitochondrion
o Rough ER
o Smooth ER
o Golgi apparatus
o Lysosome
Procedure & Inquiry
1. Ask the selected students to quickly design a labeled sign representing their organelle
2. Assign each student to an organelle and hand them the appropriate label.
3. Then ask the student to give a two-minute description of their relationship to the other
organelles, for example I take _______ from the nucleus and provide the Golgi apparatus
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with ______.
4. The other organelles are free to discuss any interrelationships not mentioned by the other
organelles.
5. Ask the class assess the accuracy of the information discussed by the organelles.
6. Then ask the class to do a “Survivor-style” vote to determine which organelle could be
“voted out” without outright killing the cell.
A. Cytoskeleton in Action
Introduction
Seeing the activity of an organelle by demonstrating a living model is an excellent means
of reinforcing the learning of cell structure. Elodea is a simple to use model for demonstrating
cytoskeleton activity. Students can envision the nature and complexity of the cytoskeleton
arrangement by tracking the path of chloroplasts traveling around the elodea leaf cytoskeleton.
Materials
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Microscope attached to a video camera
LCD projector linked to the video camera
Fresh elodea in 300C water
Slide with cover slip
1 cigarette soaked overnight in 5 ml 30% ethanol solution
Procedure & Inquiry
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Prepare a wet mount of one elodea leave
Project a leaf under high magnification for viewing by the class
Ask to students to observe and discuss any pattern of movement by the chloroplasts
Ask the class to hypothesize why the chloroplasts are being moved around the by
cytoskeleton and what factors, such as direction of sunlight irradiation, would affect
chloroplast movement
Tell the class you are going to add cigarette extract to the elodea
Then add on drop of the cigarette solution onto the slide while it is still on the stage
Ask the students to observe what happens (the chloroplasts will stop moving)
Have the class hypothesize the reason for the loss of chloroplast movement
USEFUL INTERNET RESOURCES
1. Case studies are excellent for reinforcing scientific concepts. Iowa State University
produced an interesting case study that assesses the use of cells and organs in human
medicine. This case study can be done in class or be given as a take-home. The case
study can be found at http://www.bioethics.iastate.edu/classroom/organtransplants.html.
2. Animations are entertaining educational tools that support the content covered in a
lecture. The Virtual Cell Website was designed for high school use but has interactive
animations useful for demonstrating general cell anatomy. The website can be found at
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http://www.ibiblio.org/virtualcell/index.htm.
3. Researchers used detailed graphic representations of cells and molecules as a way of
better understanding cell function and structure. Virtual Cell, produced by the University
of Illinois, provides scientifically accurate depictions of plant cell components. The
illustrations are interactive and cover molecular details about many organelles. This
website is available at http://www.life.uiuc.edu/plantbio/cell/.
4. Tissue engineering is a new and exciting field of science that uses cell biology
knowledge to produce transplant materials. It is a rapidly growing field that reinforces to
students the need to remember that cells function within a hierarchical system of
complexity. The Tissue Engineering Website can be used to show students advances in
the production of artificial tissues and organs used in medicine. The website can be found
at http://www.tissueeng.net/.
LABORATORY IDEAS
A. Cell Chemistry
a. Have students use the microscope to investigate the chemistry of living cells.
b. Tell the class that you want students to explore the chemistry of cell components.
They should be asked to draw and record in writing their observation of the cells
being investigated.
c. Provide students with the following materials:
i. Microscope
ii. 8 microscope slides and cover slips
iii. Scalpels
iv. Forceps
v. Toothpicks
vi. Dimethyl Sulfoxide (DMSO)
vii. Potassium Iodide (IKI) or Lugol’s solution
viii. Concentrated Sudan IV solution
ix. Biuret reagent
x. Hematoxylin stain
xi. Droppers
xii. Potato
d. Explain to students the different molecules that are detected using the various
stains:
i. Potassium Iodide - starch
ii. Sudan IV solution - lipids
iii. Biuret reagent - proteins
iv. Hematoxylin stain – nucleic acids
e. Tell students that they are going to compare the chemical composition of plant
and animal cells. They are going to do this using by potato cells and human cheek
cells as models.
f. Have students carry out the following procedure:
i. Prepare 4 wet mounts of thin potato slivers
1. Add 1 drop DMSO to all slides
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2. Add stains:
a. 1 drop of potassium Iodide
b. 2 drops of sudan IV solution
c. 2 drops of Biuret reagent
d. 2 drops of hematoxylin stain
3. Students should let slides sit for 1 minute and then observe under
the microscope.
ii. Prepare 4 wet mounts of cheek cells
1. Carefully remove cheek cells with toothpick
2. Add 1 drop DMSO to all slides
3. Add stains:
a. 1 drop of potassium Iodide
b. 2 drops of sudan IV solution
c. 2 drops of Biuret reagent
d. 2 drops of hematoxylin stain
4. Students should let slides sit for 1 minute and then observe under
the microscope.
g. Ask the students to note any differences in molecular composition between the
animal and plant cells.
h. Use proper safety precautions and dispose of reagents appropriately according to
the MSDS.
B. Detection of Catalosomes
a. Catalosomes of one of many small vacuoles that carry out specific cell functions.
b. Students can investigate the presence of catalosomes using a simple hydrogen
peroxide test for the presence of catalase.
c. Provide students with the following materials:
i. Microscope
ii. 2 microscope slides and cover slips
iii. Scalpels
iv. Forceps
v. Medical grade hydrogen peroxide
vi. Droppers
vii. Dimethyl Sulfoxide (DMSO)
viii. Potato
ix. Elodea leaves
x. Onion roots
d. Explain to students they will be looking for organelles called catalosomes and
detecting them by looking at metabolic activity of the organelle.
e. Then describe that catalase is able to convert hydrogen peroxide into water and
oxygen gas. Ask them to hypothesize how they could determine if the reaction is
taking place and to what degree it is occurring.
f. Instruct students to carry out the following procedure:
i. Prepare a wet mounts of potato cells
1. Add 1 drop DMSO to all slides
2. Add hydrogen peroxide and immediately view under the
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microscope
ii. Prepare a wet mounts of elodea cells
1. Add 1 drop DMSO to all slides
2. Add hydrogen peroxide and immediately view under the
microscope
iii. Prepare a wet mounts of onion root cells
1. Add 1 drop DMSO to all slides
2. Add hydrogen peroxide and immediately view under the
microscope
g. Ask students to describe where the catalosomes appear to be located in the
particular cells and explain any differences seen in catalosome activity between
the different specimens.
h. Use proper safety precautions and dispose of reagents appropriately according to
the MSDS.
LEARNING THROUGH SERVICE
Service learning is a strategy of teaching, learning and reflective assessment that merges the
academic curriculum with meaningful community service. As a teaching methodology, it falls
under the category of experiential education. It is a way students can carry out volunteer projects
in the community for public agencies, nonprofit agencies, civic groups, charitable organizations,
and governmental organizations. It encourages critical thinking and reinforces many of the
concepts learned in a course.
Students who have successfully mastered the content of Chapter 5 can apply their knowledge for
service learning activities in the following ways:
1. Have students take part is a health fair by providing information about the cellular
damage caused by smoking.
2. Have students provide background information about stem cells to a civic group.
3. Have students tutor middle school or high school biology students studying cell structure.
4. Have students judge science fair projects related cell structure and function.
This project is funded by a grant awarded under the President’s Community Based Job Training Grant as implemented by the U.S.
Department of Labor’s Employment and Training Administration (CB-15-162-06-60). NCC is an equal opportunity employer and
does not discriminate on the following basis:
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against any individual in the United States, on the basis of race, color, religion, sex, national origin, age disability, political
affiliation or belief; and
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against any beneficiary of programs financially assisted under Title I of the Workforce Investment Act of 1998 (WIA), on
the basis of the beneficiary’s citizenship/status as a lawfully admitted immigrant authorized to work in the United States, or
his or her participation in any WIA Title I-financially assisted program or activity.
This workforce solution was funded by a grant awarded under the President’s CommunityBased Job Training Grants as implemented by the U.S. Department of Labor’s Employment
and Training Administration. The solution was created by the grantee and does not
necessarily reflect the official position of the U.S. Department of Labor. The Department of
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Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with
respect to such information, including any information on linked sites and including, but not
limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy,
continued availability, or ownership. This solution is copyrighted by the institution that
created it. Internal use by an organization and/or personal use by an individual for noncommercial purposes is permissible. All other uses require the prior authorization of the
copyright owner.
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