Download Observing Specialized Cells Lab

Name______________________________
Chapter 10
Class __________________
Date ______________
Cell Growth and Division
Observing Specialized Cells
Introduction
You may want to refer students to Section 7–4 in
the textbook for a discussion of tissue and organ
formation.
Time required: 50 minutes
The cell is the basic unit of structure and function in all living things.
All of the processes necessary for life occur in cells. In single-celled
organisms, such as amoebas, all of the functions required by the
organism take place within one cell. Multicellular organisms, such
as humans and plants, are made up of many cells with different
structures and functions. The shape and size of a cell, as well as the
structures found inside it, are determined by the functions of the cell.
In this investigation, you will observe several different types of cells.
You will compare and contrast the structures you see in the cells, and
relate the structures to the functions the different cells perform.
Problem
How are the structures of specialized cells adapted to fit their
particular functions?
Pre-Lab Discussion
Read the entire investigation. Then, work with a partner to
answer the following questions.
1. What types of cells have a cell membrane, cytoplasm, and a
nucleus? Where would you expect to find the cytoplasm in a cell?
All plant and animal cells have these structures. The cytoplasm is found between the cell membrane
and the nucleus.
2. In what types of cells would you expect to see a cell wall?
Plant cells.
3. Saclike structures called vacuoles are found in many cells. What is
the function of vacuoles?
Vacuoles store materials such as water, salts, proteins, and carbohydrates.
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4. An organelle is a cell structure with a specialized function. Plastids
are plant organelles. Which plastid traps the energy of sunlight and
converts it into chemical energy?
Chloroplast.
5. The outer layer of cells of a leaf is called the epidermis. These cells
protect the tissues inside the leaf by slowing down the loss of water
through evaporation. Predict what these cells will look like.
Students may predict that the cells will be stacked closely together like bricks in a wall.
6. Some functions are exclusive to plants, while others are performed
only by animals. Which specialized cells or tissues would you
expect to find only in plants? Only in animals?
Specialized cells such as guard cells are found only in plants. Bone, connective, and nerve tissues are
found only in animals.
Biology Laboratory Manual B/Chapter 10 95
Materials (per group)
compound light microscope
lens paper
lettuce leaf
A common freshwater aquarium plant is Elodea. This plant is generally available from pet
water plant leaf
stores or can be collected throughout most of the year from ponds and slow-moving
dropper pipette
streams. To maintain Elodea in the classroom, fill an aquarium or large (4 liter) glass jar
2 microscope slides with pond or spring water. If pond or spring water is not available, fill the container with tap
water and set it aside uncovered for at least 24 hours before introducing the Elodea. Float
2 coverslips
Elodea sprigs loosely on the surface of the water. If Elodea is banned as a weed in your
forceps
area, alternative water plants are available from aquarium shops and biological suppliers.
dissecting probe
prepared slides of 3 types of human tissues Obtain prepared slides of human tissues from biological
supply houses. Slides may include the following tissues:
skeletal, muscle, blood, nerve, bone, skin.
Safety
Put on a laboratory apron. Handle all glassware and sharp tools
carefully. Always handle the microscope with extreme care. If you are
using a microscope with a lamp, follow all safety rules related to
electrical equipment. You are responsible for its proper care and use.
Use caution when handling microscope slides, as they can break easily
and cut you. Note all safety alert symbols and review the meaning of
each symbol by referring to Safety Symbols on page 8.
Procedure
1. Obtain a microscope and place it about 10 centimeters from the
edge of the laboratory table.
2. Carefully clean the eyepiece and the objective lenses with lens paper.
3. Locate a rib in the lettuce leaf. As shown in Figure 1, bend the
lettuce leaf against the curve until it snaps.
Bend leaf
against curve
Figure 1
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Biology Laboratory Manual B/Chapter 10
Remove
lower epidermis
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B
A
Name______________________________
Class __________________
Date ______________
4. With the forceps, carefully remove the thin layer of tissue called the
epidermis from the piece of lettuce. Spread out the epidermis as
smoothly as possible on a microscope slide. Note: If the epidermis
becomes folded on the slide, use a dissecting probe to gently unfold and
flatten it. CAUTION: Microscope slides can break easily.
5. To prepare a wet-mount slide, place a drop of water in the center of
the slide. Using the dissecting probe, gently lower the coverslip
onto the lettuce as shown in Figure 2. CAUTION: Be careful when
handling sharp instruments.
Coverslip
Microscope slide
Dissecting probe
Figure 2
6. Observe the lettuce epidermis under the low-power objective of the
microscope. Note: It may be necessary to adjust the diaphragm so there is
sufficient light passing through the cells. Notice the irregular shapes of
the epidermal cells.
7. Switch to the high-power objective. CAUTION: When turning to the
high-power objective, you should always look at the objective from the side of
your microscope so that the objective lens does not hit or damage the slide.
8. In the Data Table on page 98, write the name of the cell that you
examined. Describe its general shape and place a check mark in the
columns below the structures that you are able to observe under the
high-power objective.
9. In the appropriate place on page 98, draw and label what you see
under the high-power objective. Record the magnification of the
microscope.
10. Repeat steps 5 to 9 using the water plant leaf.
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11. Repeat steps 6 to 9 using the 3 prepared slides of human cells
and/or tissues. Draw and label what you see in the appropriate
place on pages 98 and 99.
Biology Laboratory Manual B/Chapter 10 97
Data Table
Plastids
Vacuoles
Cytoplasm
Nuclear envelope
Nucleus
Shape
Cell wall
Cell Type
Cell membrane
Cell Structures
Answers will depend on slides available.
Magnification __________
Lettuce epidermis
Water plant epidermis
Prepared Slide 1
Prepared Slide 2
Magnification __________
Magnification __________
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Magnification __________
Tissue _____________________________
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Biology Laboratory Manual B/Chapter 10
Tissue _____________________________
Name______________________________
Class __________________
Date ______________
Prepared Slide 3
Magnification __________
Tissue _____________________________
Analysis and Conclusions
1. Observing Do all the cells share any common structures? Explain
your answer.
Students should observe a cell membrane, a nucleus, and cytoplasm in all of the cells.
2. Comparing and Contrasting Compare the shapes of the different
cells. Describe any similarities or differences.
Answers will depend upon tissue selected.
3. Inferring What factors might affect the size and shape of a cell?
The specific function of the given cell; the pressure of adjacent cells.
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4. Comparing and Contrasting For each type of tissue that you
observed, describe one feature that is not found in any of the others.
Some possible answers may include: bone tissue has circular layers; epithelial tissue (human and plant) is flat;
blood tissue contains disk-shaped cells without nuclei and large irregularly shaped cells with nuclei; skeletal
muscle tissue is striated.
5. Analyzing Data How is each tissue you observed adapted to
perform its special function?
Answers will depend on the tissues selected.
Biology Laboratory Manual B/Chapter 10 99
6. Drawing Conclusions Why do the cells that make up the different
tissues have different shapes and sizes?
Cells with different shapes and sizes have different functions; in other words, cell shape and size are related
to cell function.
Going Further
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Obtain additional prepared slides of specialized cells and tissue from
your teacher. Prepare labeled sketches of each of these slides.
100 Biology Laboratory Manual B/Chapter 10