I. Objectives:
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A. To identify the cell organelle and their functions
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B. To name the two structures found exclusively in the plant cell
II. Background Information on the Cell
The cell is the basic unit of structure and function in all living organisms. Cells range in size from 1/200th of an inch in diameter as found in the ovum, one of the largest cells, to 1/5000th of an inch. Thus most cells are invisible to the eye without the magnification of the microscope. Until the development of the high power compound microscopes knowledge of the structure and function of the cell was greatly limited.
Our concept of the cell luckily has improved since 1665 when Robert Hooke used a primitive microscope to view wafer thin sections of cork. Hooke observed the cells were “not very deep but consisted of a great many little boxes’ separated out of one continued long pore, by certain diaphragms.” The cell theory formulated by Schleiden and Schwann in 1839 moved boldly beyond to state that all living things are composed of cells and that all cells arise from other cells.
The cell is the smallest unit of a living organism that carries on life functions. Within the human body there are more than one hundred different kinds of cells, each designed to carry on a distinct function. Although cells vary in size, shape, and function, most cell possess a very similar basic structure.
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The
nucleus
is usually the most prominent structure of the cell. It directs the activities of the cell and is especially involved with the cell’s reproductive processes.
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Within the nucleus is a tangled network of material called
chromatin
. These threads of chromatin coalesce during cell division to form chromosomes.
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A thin membrane,
the nuclear membrane
, surrounds the nucleus and regulates the passage of materials into and out of the nucleus.
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Within the nucleus are one or more spherical
chromosomes
, composed of deoxyribonucleic acid and proteins that are visible only during the cell’s reproductive phase.
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The
cell membrane i
s a thin saclike covering of the cell. It regulates the entrance of materials needed for cell growth into the cell as well as the exit of cellular waste products through minute pores in the membrane.
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The
cytoplasm
is the viscous material between the cell membrane and the nuclear membrane.
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The
mitochondria
are found in the cytoplasm and vary in number from cell to cell. They are centers of cellular respiration and energy-producing metabolism.
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The
endoplasmic reticulum
found in the cytoplasm are minute two-walled membranes that function like a canal system connecting the cell and nuclear membranes. They transport as well as store materials.
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Ribosomes
are tiny cellular bodies found on the endoplasmic reticulum. They are sites of protein production used for cellular growth, repair,and reproduction. Enzymes, controlling the rate of metabolism are made in the ribosomes.
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Lysosomes
, located in the cytoplasm, contain enzymes that break down macromolecules into smaller molecules so they may be oxidized in the mitochondria.
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Golgi Bodies
, or Golgi complex, are also in the cytoplasm. They function as accumulating and concentrating areas for secretions of proteins.
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Centrioles
are small paired cylindrical bodies located near the nucleus and function in cell division.
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Vacuoles
are bubblelike spaces found in the cytoplasm and used to regulate and store water, food, and cellular waste products.
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The
cell wall
is a rigid structure made of cellulose surrounding the cell membrane providing strength and support to the plant cell.
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Chloroplasts
are tiny structures found in the plant cell containing chlorophyll.
III. Lesson Plans/ Activities
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A. Viewing prepared slides
Obtain prepared slides from a science supply house of plant and animal cells to facilitate the visualization of the cell.
Using various types of cells, i.e. blood, muscle, neuron, etc. the students will realize that there are numerous types of cells, each with its own size and distinctive shape but all possessing standard characteristics such as the nucleus, cell membrane, cytoplasm, vacuoles.
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B. Making slides
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1. Duplicate Robert Hooke’s observation of cork cells. use a single-edged razor blade to cut a thin slice of cork. Place the cork on the slide under the microscope to observe. Just as Hooke observed over four hundred years ago, rows of tiny empty boxes can be seen.Since the cork is dead material,only the nonliving material cellulose composing the cell wall can be seen.
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2. Take the inner leaf of an onion and slice a 1/4 inch square on the inner side of the leaf. Mount and stain. You should be able to observe the nucleus, cytoplasm, cell membrane and cell wall.
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3. Place a drop of water on the slide and add an elodea leaf. Stain with iodine and cover with slip. Cell organelles should be visible under low microscopic power.
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4. Obtain an amoeba either from a supply house or pond water. Place a drop of water on the slide and cover. Examine under a microscope at low power to focus. Change to a higher power to observe organelles.
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C. Drawing the cell
Using reference material, have students draw stylized plant and animal cells. Also view and draw various types of cells to illustrate the diversity in size and shape while emphasizing the commonality of certain cell organelles.
D. Three dimensional model
We usually picture the cell in two dimensions. To develop a more accurate concept a three-dimensional model would be appropriate.
Obtain a clear plastic container of some sort, the type used for food storage is fine. Prepare a package of gelatin and allow it to begin to congeal. Before completely set use various food items to represent cell organelles. Have the class determine what items would be most appropriate. Making a tasty salad as well as an accurate model can be a task requiring much thought. Some suggestions might include hard boiled eggs or brussel sprouts as nuclei; shredded carrots or pickled eggplant provide convincing endoplasmic reticulum;mini chocolate chips could be used for ribosomes. Allow mold to set completely. Bon Appetite if you dare.
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5. View film
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Obtain VCR tape of “The Fantastic Voyage”. In this old science fiction film, a crew of scientists and doctors and their equipment are miniaturized to be inserted into the ailing body of some eminent scientist to repair damage. It includes sequences that depict the functions of cells and organs. It also serves to help explain the concept of cell size as various small objects are shown as massive obstacles to be overcome throughout the voyage.
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Innerspace here we come. Enjoyable and informative.
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6. Vocabulary puzzle sheet
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On separate sheet
