Name ______________________________ Date ___________ Per _______
Comparing Cell Types
OBJECTIVES
After completing this lab you should be able to:
1. Compare and contrast prokaryotic and eukaryotic cells.
2. Prepare wet mount slides of eukaryotic cells.
3. Study and locate under the microscope six specific cell parts - cell wall, cell membrane, cytoplasm, nucleus, nucleolus and
chloroplasts.
4.
Compare the cell parts found in plant and animal cells.
MATERIALS
Microscope
Coverslips
Water
Microscope slides
Pipette
Methylene blue stain
Onion Slide
Toothpicks
Privet Leaf Cells Slide
Bacterial Cell Slide
In the 17th century Robert Hooke built a microscope powerful enough to see objects at greater magnification than had previously
been possible. Hooke used his microscope to examine a thin piece of cork. While viewing this section of cork, he observed many
individual units making up the cork. He published a report in 1655 in which he called these units “cells” because they reminded him
of the small cubicles in which monks lived.
Other scientists began to use microscopes to examine many different plants and animals and these scientists often saw structures
that reminded them of the cork cells Hooke described. Over the next 150 years, scientists realized that all living things are composed
of cells.
With better microscopes, scientists observed that although cells vary in organization, size, and function, all cells have the following
structures:
• A plasma membrane defining the boundary of the living material,
• A region of DNA (deoxyribonucleic acid), which holds the genetic information, and
• A cytoplasm (everything inside the plasma membrane that is not part of the DNA region).
There are two basic types of cells: eukaryotic, those with a clearly defined nucleus and membrane-bound organelles, and
prokaryotic, those without a nucleus and membrane-bound organelles. The Greek word karyon means kernel, referring to
the nucleus. Thus, prokaryotic means “before a nucleus”, while eukaryotic means true nucleus. The table below compares
the characteristics of prokaryotic and eukaryotic cells.
Characteristics
Genetic
Material
Cytoplasm
Prokaryotic Cells
Located in nucleoid (region of cytoplasm not
bounded by membrane)
Consists of a single, circular DNA molecule
Has no associated proteins
Small ribosomes (70s). Photosynthetic
membranes arising from the plasma membrane in
some species.
Eukaryotic Cells
Located in nucleus (membrane-bound compartment within
the cytoplasm)
Made up of DNA molecules associated with proteins.
Organized into linear chromosomes.
Large ribosomes (80s). Membrane-bound organelles
present. Organelles are compartments which perform
specific cell functions.
PART I: PROKARYOTIC CELLS (BACTERIAL CELLS)
1. Observe the microscopic structure of the bacteria on demonstration. Draw the specimen at high power and label the
magnification in the space below.
Magnification _________
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2.
Return the slide to your instructor when you are finished.
Examine the drawing of the bacterium Escherichia coli below. The cell has a cell wall, a structure different from the wall of plant cells
but serving the same primary function. The plasma membrane is flat against the cell wall and may be difficult to see. Look for two
components in the cytoplasm: the small block dots called ribosomes give the cytoplasm its granular appearance; the nucleoid, a
relatively region (appears light) containing fine threads of DNA.
Label the structures highlighted structures discussed above on the diagram below.
Part II: Eukaryotic Cells – Animal Cells (Cheek Cells)
1. Obtain a clean toothpick, slide, and cover-slip.
2. Use a clean toothpick to gently scrape the inside of your cheek. (You will not be able to see anything on the toothpick)
3. Add ONE drop of methylene blue from the pipette to the slide. Roll the toothpick with your cheek cells in the drop. Add a cover
slip and throw the toothpick in the trash.
4. Locate the cheek cells using low power, then switch to middle power, then switch to high power. Find the nucleus, a round
centrally located body within each cell.
6. Carefully draw several cells as they appear under the microscope under high power and label the magnification in the space
below. Label the cytoplasm, nucleus, and plasma membrane. Record the magnification used.
7. Clean off your slides, dry them and return them to your instructor.
HINT: Locate and examine cells that are separated from one another rather than those that are in clumps.
Magnification ___________
Part II: Eukaryotic Cells – Plant Cells (ONION CELLS)
1. An onion epidermal cell slide has been prepared.
2. Observe the fixed slides with your microscope under low power, then switch to middle power, then switch to high power.
3. The nucleus will be a large sphere within the cytoplasm. Examine the nucleus carefully and you will spot several nucleoli inside the
nucleus. Nucleoli are the areas within the nucleus were RNA (ribonucleic acid) is produced. The rest of the nucleus is largely DNA.
4. Carefully draw several onion epidermal cells under high power and label the magnification in the space below.
Label the nucleus, cell wall, cell membrane, and cytoplasm.
5. Return the slide to your instructor when you are finished.
Magnification ______
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Part II: Eukaryotic Cells--Plant Cells (PRIVET LEAF CELLS)
7. An privet leaf cell slide has been prepared.
8. Carefully draw several privet leaf cells. Draw the specimen under high power in the space below. Label the chloroplasts, nucleus
(if seen; it may be hard to see), cell wall, cell membrane, and cytoplasm and any other organelles you can make out.
9. Return the slide to your instructor when you are finished.
Magnification ______
Analysis Part A
ONION CELLS-Cell wall, Cell membrane, Nucleus, Cytoplasm
1.Describe the shape of an onion cell:
2. a) Are onion cells produced by plants or animals?
b) How do you know?
3.What is the function of a cell’s nucleus?
CHEEK CELLS-The Cell Membrane, Cytoplasm, and Nucleus
1. Describe the shape of a cheek cell:
2.
a) Are cheek cells produced by plants or animals?
b) How do you know?
3.
Are cheek cells alive? Explain.
PRIVET LEAF -Cell Wall, Cell Membrane, Cytoplasm, and Chloroplast
1.Describe the shape of a lettuce cell:
2. a) Are lettuce cells from a plant or animal cells?
b) Provide two pieces of evidence to defend your answer in 2a.
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3.Describe the:
a) color of the chloroplast
b) function of the chloroplast?
Analysis Part B
1) Determine if each of the following characteristics is true of Prokaryotic cells, Eukaryotic cells, or Both cell types.
______ No membrane-bound nucleus
______ Membrane-bound nucleus
______ No membrane-bound organelles
______ Contains membrane-bound organelles
______ Small ribosomes present
______ Large ribosomes present
______ Cell membrane present
______ Chromosomes present
______ Cytoplasm present
______ Mitochondria, endoplasmic reticulum, Golgi, and vacuoles present
______ Genetic material is linearly arranged
2) How does the size of the bacterial cell observed compare with the size of the eukaryote cells you viewed? Explain.
3) Name 4 structures common to all cells.
4) Name 3 differences between plant and animal cells.
5) Mitochondria and chloroplasts have their own DNA and ribosomes. What does this tell you about their possible origin?
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