Student Learning Outcomes

At the completion of this exercise, the student will be able to:

1) State the cell theory2) Discuss the factor that limits the cell size3) Define and five example of unicellular, colonial, and multicellular organisms4) Compare and contrast prokaryotic and eukaryotic cells5) Describe the basic anatomy of a typical prokaryotic cell6) Compare and contrast plant and animal cells7) Describe the basic anatomy of a plant cell and an animal cell8) Perform microscopic observations of bacteria, protist, fungi, plant and animal cells.

OVERVIEW

From tiny bacteria to the great blue whale, the cell serves as the fundamental building block of all living things. A student reading this paragraph consist of nearly 125 trillion cells working together to maintain a state of biological balance, or homeostasis. Even the hamburger and fries sitting next to this manual are made up of a multitude of plant and animal cells. Yes, that burger and fries also have their share of bacterial cells.

The cell is the smallest unit of biological organization that can undergo the activities associated with life, such as metabolism, response, and reproduction. The British scientist Robert Hooke first described the cell in 1665. In the late 1830s, two German scientists – the botanist Matthias Schleiden and the zoologist Theodor Schwann – provided a powerful understanding of the structure and function of plant and animal cells through the cell theory. Basically the cell theory states that all living things are composed of cells and that the cell is the basis unit of structure and function of all living things.

In the 1850s, the German physician Rudolph Virchow added to the cell theory that cells come only from preexisting cells. Virchow also pointed out that the cell is the fundamental link in the biological levels of organization that include tissues, organs, systems, and ultimately the completer organism. Today, the biological levels or organization have been expanded to include populations, communities, ecosystems, and the biosphere.

Although cells vary in size from a bacterium 1 to 10 micrometers in diameter to a chicken egg larger than 1 centimeter in diameter, most cells are microscopic.

The inclusions and organelles within the cell are much smaller and are measured in nanometers. The reason for the absence of giant cells is a matter of the surface area – to – volume ratio. If the surface area of a cell increases, the volume does not increase in a direct proportion; the volume increases proportionally faster. Thus, the surface area could not support the metabolic needs of the increased volume. Some cells, such as frog eggs, chicken eggs, and ostrich eggs, can become large because they are not metabolically active until they begin to

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Chapter 6. THE STRUCTURE AND FUNCTION CELLS: BLOCKS OF LIFE

divide. Other cells, such as nerve cells, can possess extensions of more than a meter, but the extensions are narrow and have little volume.

Bacteria and many protists, such as the green alga Spirogyra and the protozoan paramecium, are composed of one cell and called unicellular. Despite having just one cell, these organisms carry on all of the life processes efficiently. Several species of protists exist as colonies that are loosely connected groups or aggregates of cells. Examples of colonial organisms are the alga Volvox and Scenedesmus. Organisms such as an azalea, a mushroom, and a walrus, which are composed of many cells, are called multicellular. These organisms exhibit a division of labor and have a variety of specialized tissues.

Although innumerable forms of cells exist in nature, only two basic types of cells comprise life on Earth: prokaryotics and eukaryotic cells.

Prokaryotic Cells:

1. Lack a membrane – bound nucleus and organelles.2. Much smaller than eukaryotic cells.3. The cytoplasm of prokaryotic is surrounded by a plasma membrane.4. The majority of prokaryotics are encased in a protective cell wall.5. Prokaryotics organisms are placed within the kingdom Archaebacteria and Eubacteria

Eukaryotic Cells:

1. More structurally complex and larger than prokaryotic cells2. They have a membrane – bound nucleus and organelles.3. Members of the kingdom Protista, Plantae, Fungi, and Animalia possess eukaryotic

cells.

PROKARYOTIC CELLS

The most cosmopolitan organisms on Earth today are the prokaryotes. They exist in every possible environment, even those that do not seem conducive of life. Although the prokaryotes are small in size 1 to 50 micrometers(µm) in width and diameter, they are economically, ecologically, and medically important. Two distinct groups of prokaryotic organisms are archaebacteria and bacteria. Bacterial fossils have been dated at older than 3.5 billion years.

1) The archaebacteria , or ancient bacteria can be found living in extreme environments such as exceedingly salty habitats (extreme halophiles), exceptionally hot environments (extreme thermophiles), the anaerobic mud of swamps, and the gut of termites and many mammals (methanogens).

2) The eubacteria , or true bacteria, are better known to the general public. Although the majority of eubacteria are harmless or helpful, such as Lactobacillus acidophilus, which is placed in yogurt, there are several medically important species. Examples of these organisms are Yersinia pestis (black plague), Clostridium perfringens (gangrene), Heliobacter pylori (ulcers), Vibrio cholerae (cholera), Staphylococcus aureus (boils), and Bacillus anthracis (anthrax)

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Identify the bacterial species responsible for five diseases in humans that are not mentioned above.

(1) _____________________________________________________________________

(2) _____________________________________________________________________

(3) _____________________________________________________________________

(4) _____________________________________________________________________

(5) _____________________________________________________________________

OBSERVNG CYANOBACTERIA

The cyanobacteria , once classified as the blue – green algae , are photosynthetic eubacteria. These rather large prokaryotes do not possess chloroplasts; the chlorophyll a is located in the thylakoid membranes. The cyanobacteria have a number of accessory pigments that can mask the green color of chlorophyll. As a result, species of cyanobateria appear red, yellow, brown, or blue – green. The cyanobacteria are common and can be found in a number of environments, including in the soil, on sidewalks, on the sides of buildings, on trees, and in bodies of water such as ditches.

Name three environments where cyanobacteria are found.

(1) _____________________________________________________________________

(2) _____________________________________________________________________

(3) _____________________________________________________________________

PROCEDURE 6.1

OBSERVING CYANOBACTERIA

Materials

Microscope Prepared slides of cyanobacteria (Gloeocapsa, Nostoc, Oscillatoria, and Anabaena.) Blank glass slides, oil immersion, lens cleaner, and cover slips Forceps and plastic disposable pipets NOTE: If available! Make a wet mount of living specimens (water from the fish tank)

of the following cyanobacteria: Gloeocapsa, Nostoc, Oscillatoria, and Anabaena .

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1) Obtain a microscope and using proper microscopy techniques, observe the prepared slides of Gloeocapsa at oil immersion 1000X (White objective) and Nostoc at total magnification of 400X (Blue objective).

2) Take a picture or sketch and describe Gloeocapsa at 1000X .

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3) Take a picture or sketch and describe Nostoc at 400X .

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_______________________________________________________________________

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Heterocys

Akenete

4) Obtain a microscope and the prepared slides of Oscillatoria and Anabaena.5) Using proper microscopy techniques, observe Oscillatoria at total magnification of 400X

(Blue objective) and Anabaena at oil immersion 1000X (White objective).

6) Take a picture or sketch and describe Oscillatoria at 400X .

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7) Take a picture or sketch and describe Anabaena at 1000X .

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________________________________________________________________________

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8) After completion of the activity, clean up your work area and return or dispose of the materials as instructed.

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Heterocys

Akenete

Each segment is a cell

OBSERVNG BACTERIA

Most bacteria are significantly smaller than the cyanobacteria. The bacteria are simple in form and anatomy and exhibit three basis shapes: bacillus (rod – shaped), coccus (spherical – shaped), and spirillum (spiral – shaped). An electron microscope is used to observe the anatomical detail of a typical bacterium.

Materials

Microscope Immersion oil Prepared slides of Escherichia coli, Helicobacter pylori, Treponema pallidum, and

Streptococcus pyogenes. Blank glass slides and cover slips Toothpick Pipette Plain yogurt

OBSERVING BACTERIA

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1. Using proper microscopy techniques, observe the prepared slides of Escherichia coli, Treponema pallidum, and Streptococcus pyogenes. To view the specimens properly, use an

oil immersion 1000X (White objective).

Take a picture or sketch and describe (label all visible organelles) the three shapes of bacteria bacillus, coccus, and spirillum at 1000X.

__________________________________ _________________________________

_________________________________

Note: After use, ensure that all oil is removed from the stage, oil immersion objective, and slide.

PROCEDURE 6.2

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1) Obtain a microscope, immersion oil, prepared slides, blank glass slides, cover slips and toothpicks.

2) Using proper microscopy techniques, observe the prepared slides of Escherichia coli and Helicobacter pylori. To view the specimens properly, use an oil immersion 1000X (White objective).

3) Take a picture or sketch and describe Escherichia coli at 1000X .

_________________________________________________________________________

4. Take a picture or sketch and describe Helicobacter pylori at 1000X .

__________________________________________________________________________

__________________________________________________________________________

[Note: After use, ensure that all oil is removed from the stage, oil immersion objective, and slide.]

1) Obtain a small amount of plain yogurt on the tip of a toothpick. Rub the yogurt onto the central portion of a blank glass slide. Place on e drop of water on the yogurt with a

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pipette, and mix with a toothpick. Gently place the cover slip on the water/yogurt mixture.

2) Observe the bacteria in the yogurt under high power (400X) then oil immersion (1000X). The majority of bacterial cells in yogurt are Lactobacillus acidophilus.

3) Take a picture or sketch and describe Lactobacillus at 1000X .

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Why is Lactobacillus used in yogurt?

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Why it the presence of Lactobacillus in yogurt considered beneficial to your health?

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[* Note: After completing the activity, clean up your work area and return or dispose of the materials as instructed.]

Structure FunctionsCell Wall In eubacteria, a peptidoglycan envelope that provides protection and shape

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Plasma Membrane A phospholipid bilayer that provides support and regulates the movement of substances into and out of the cell.

Cytoplasm Semifluid medium within the cellNucleoid Region that houses the bacterial DNA in a single chromosome. Some

bacteria possess small circular fragments of DNA called plasmids.Ribosome Site of protein synthesisFimbriae Short hair – like structures that aid in attachment

Pili Rigid hair – like structures that are important for attachment and the exchange of genetic information.

Flagellum An elongated structure used for locomotion. The number of flagella and their location are important in determining the species of bacteria

Capsule A protective slime – like are lying outside the cell wall. It helps the bacterium adhere to certain surfaces, keeps it from drying out, and protects the bacterium from phagocytosis by other organisms or cells.

Table 1 display the most common Anatomical features of a Generalized Bacterium

EUKARYOTIC CELLS

Eukaryotic cells had their origins nearly 2 billion years ago. Eukaryotes include the protists, fungi, plants, and animals. The cells of eukaryotes possess a membrane – bound nucleus and a variety of membrane – bound organelles.

OBSERVING PROTIST

Protists include a diverse group of organisms. In fact, the former kingdom Protista is undergoing reorganization and one day will consist of several new kingdoms. Presently, the protists can be separated into the plant – like protists (algae), fungi – like protists (slime and water molds), and animal – like protists (protozoans). The protists are discussed in more depth in chapter 21.

PROCEDURE 6.3

Materials

Microscope Immersion oil Prepared slides of Volvox and

Amoeba preteus Blank glass slides and cover slips

Toothpicks Pipette Culture of Spirogyra and

Paramecium sp. If available. Protoslo

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1) Obtain a microscope, prepared slides, blank glass slides, cover slips, and toothpicks.2) Using proper microscopy techniques, observe the prepared slides of the colonial alga

Volvox sp at high power (Blue objective 40X) and the protozoan Amoeba proteus at high power (Blue objective 40X) or oil immersion (White objective 100x).

3) Take a picture or sketch and describe Volvox sp at 400X .

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_________________________________________________________________________

4) Take a picture or sketch and describe Amoeba proteus at 400X or 1000X .

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[* Note: After completing the activity, clean up your work area and return or dispose of the materials as instructed.]

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5) If available carefully prepared a wet mount of Spirogyra and Paramecium sp. and observe the living protists. Protoslo may have to be added to the slide with paramecia to slow them down for observational purposes. Note: use the prepared slides of Spirogyra at high power (yellow 10X or Blue objective 40X) and Paramecium sp. at high power (Blue objective 40X or oil immersion White objective 100X), which are available!

6) Take a picture or sketch and describe Spirogyra at 100X or 400X .

_____________________________________________________________________________

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1) Take a picture or sketch and describe Paramecium sp. at 400X or 1000X .

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____________________________________________________________________________

[* Note: After completing the activity, clean up your work area and return or dispose of the materials as instructed.]

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PLANT AND ANIMAL CELLS

Kingdom Plantae and Animalia include the most conspicuous organisms on Earth. The plan kingdom contains approximately 280,000 species of multicellular, photosynthesis autotrophs. Plants vary in size and complexity from the minute duckweed to the giant redwood tree. Kingdom Animalia encompasses more than 1.5 million species of multicellular heterotrophs. Members of the animal kingdom vary tremendously, from simple sponges to humans. The plants and animals are discussed in more depth in later chapters.

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OBSERVING PLANT CELLS

Elodea is a common plant that lives in freshwater habitats such as ponds and lakes. It provides an excellent example for studying basic plant cell anatomy. The leaves of Elodea are only a few cells thick and allow light to pass through the leaf without special preparation techniques.

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Common Anatomical Features of Eukaryotic Cells

Structure FunctionCell wall In plant cells, a cellulose envelope that provides protection and

shape.Plasma membrane A phospholipid bilayer that provides support and regulates the

movement of substances into and out of the cell.Cytoplasm A semifluid medium located between the plasma membrane and

nucleus. Inclusions and organelles are found in the cytoplasm.Nucleus The control center of the cell.

Nuclear envelope Membrane surrounding the nucleus; possesses numerous nuclear pores.

Nucleoplasm Cytoplasm with the nucleusNucleolus Chromatin – rich region that serves to combine proteins and

RNA to make ribosomal subunits. Many cells possess numerous nucleoli.

Chromatin Diffuse thread – like strands composed of DNA and proteinsMitochondrion Sire of aerobic cellular respiration

Endoplasmic reticulum (ER) Network of membranes throughout the cytoplasm. Synthesis of protein and non – protein products.

Rough ER Lined with ribosomes. Involved in the synthesis and assembly of a variety of proteins, and production of membranes.

Smooth ER Not associated with ribosomes. Main sire of steroid, fatty acid, and phospholipid synthesis. Site of detoxification.

Golgi apparatus Stacks of flattened membranous sacs or cisternae. Receives, packages, stores, and ships protein products. Produces lysosomes and other vesicles.

Peroxisome Vesicle containing enzymes that helps in breaking down fatty acids and neutralizing hydrogen peroxide.

Lysosome In animal cells, vesicle containing hydrolytic digestive enzymes that are used in destroying cellular debris and worn – out organelles. Also important in programmed cell death.

Centrioles Found in animal cells with the exception of roundworms (nematodes). Appear as a pair of cylindrical structures made of microtubules. Form the spindle apparatus in cell division.

Ribosomes Sites of protein synthesisCytoskeleton Structures that help the cell maintain its shape, anchor

organelles, and move. Three kinds of cytoskeletal elements are recognized: microtubules, microfilaments, and intermediate fibers.

Chloroplasts In plant cells, they are sites of photosynthesis. Contain grana that are stacks comprised of chlorophyll rich thylakoids.

Central vacuole In plant cells, it is a large fluid – filled sac that helps maintain the shape of the cell and stores metabolites

Middle lamellae Region between adjacent plants cells that cements the cell walls together.

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PROCEDURE 6.6

Materials

1) Microscope2) Living specimen of Elodea3) Blank glass slides and cover slips4) Pipette

OBSERVING PLANT CELLS

1) Obtain a microscope, a blank glass slide, cover slips, and a pipette.2) Carefully remove a single healthy leaf from the Elodea.3) Place the leaf in a drop of water on the blank glass slide with the top surface facing

upward. (The cells on the upper surface are much larger and easier to observe). Place a cover slip over the Elodea. Periodically check the leaf, making sure that it does not dry out. If the leaf begins to dry, add a drop of water with a pipette.

4) Examine the leaf surface with the scanning and low – power objectives. Focus through the cell layers of the Elodea.

5) Take a picture or sketch, label (all visible organelles), and describe Elodea using scanning and low – power objectives.

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

6) Using the high – power objective (White 100X), examine a single cell of Elodea. Attempt to locate the structures of a plant cell. The gray – colored nucleus may be difficult to locate. The nucleus may become more evident if a drop of iodine is placed upon the leaf. In a good preparation, the nucleolus may be evident. Carefully notice if the cytoplasm and chloroplasts are moving. This process is called cytoplasmic streaming.

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7) Take a picture or sketch, label (all visible organelles), and describe Elodea at oil immersion (high power) 1000X.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

8) After completion of the activity, clean up your work area and return or dispose of the material as instructed.

CHECK YOUR UNDSTANDING

Describe the function of the components that you viewed in Elodea

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Describe the shape and size of the central vacuole

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Describe the number and shape of the chloroplasts

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Describe the location of the nucleus and the majority of the chloroplasts

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Describe and indicate the function of cytoplasmic streaming

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Describe the color of any water – soluble accessory pigments that may have appeared. What are the accessory pigments composed of, and what is their function?

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OBSERVING ANIMAL CELLS

A typical animal cell can be collected from the living of your mouth. These simple cells, known as squamous epithelial cells, are flat and thin and possess an obvious nucleus. Epithelial cells appear in regions of wear and tear and are constantly being sloughed away. In this specimen, only the cell membrane, cytoplasm, and nucleus will be easily observed.

Materials

1) Microscope2) Blank glass slides and cover slips3) Methylene blue

4) Clean toothpicks5) Pipette

PROCEDURE 6.7

1) Obtain a microscope, a blank glass slide, cover slips, clean toothpicks, and a pipette.2) Using a clean toothpick, gently shape the inside of your cheek.

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3) Place a small drop of water on a blank glass slide. Gently roll and swirl the end of the toothpick with the epithelial scrapings into the drops of water. Discard the used toothpick into the designated container.

4) Carefully place a drop of methylene blue on the drop of water. Avoid inhalation and skin contact with methylene blue. Rinse it off the skin with mild soap and water immediately, as methylene blue will stain clothing.

5) Place a cover slip over the specimen and make your observations.6) Take a picture or sketch (label all the organelles that you can observe) and describe

epithelial tissue at oil immersion 1000X.

____________________________________________________________________________

____________________________________________________________________________

7) Note: After completion of the activity, clean up your work area and return or dispose of the materials as instructed.

CHECK YOUR UNERSTANDING

Describe the function of the components that you viewed in the epithelial tissue.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Describe the shape and size of the nucleus. Did you see a nucleolus? If so, describe the nucleolus.

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REVIEW QUESTIONS

1. Compare and contrast prokaryotic and eukaryotic cells.

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2. Describe and give an example of unicellular, colonial, and multicellular organisms.

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3. What factor prevents cells from becoming the size of blobs that consume city blocks in Science fiction movies?

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___________________________________________ ____________________________________________Last Name, First Name [lab partner N0. 1] Last Name, First Name [lab partner N0. 2]

_______________________________ _______________________________Last Name, First Name [lab partner N0. 3] Last Name, First Name [lab partner N0. 4]

___________________________ _______________ ____________________Section group # Date

4. Compare and contrast plant and animal cells.

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______________________________________________________________________________

5. Describe the function of the following features of a prokaryotic cell

a) Cell wall ________________________________________________________________

b) Pili ____________________________________________________________________

c) Fimbriae _______________________________________________________________

d) Nucleoid _______________________________________________________________

e) Flagellum ______________________________________________________________

6. Describe the function of the following features of a plant cell:

a) Cell wall ________________________________________________________________

b) Chloroplast ______________________________________________________________

c) Central vacuole __________________________________________________________

d) Middle lamellae __________________________________________________________

e) Cytoplasm ______________________________________________________________

7. Describe the function of the following structures:

a) Mitochondrion ___________________________________________________________

b) Plasma membrane ________________________________________________________

c) Nucleus ________________________________________________________________

d) Golgi apparatus __________________________________________________________

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e) Lysosomes ____________________________________________________________

f) Chromatin ____________________________________________________________

g) Peroxisomes ___________________________________________________________

h) Rough ER ____________________________________________________________

i) Smooth ER ___________________________________________________________

8. Label the anatomical features of the bacterium below.

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