Download LEARNING OBJECTIVE 3: Explain how the components of a cell`s

CHAPTER 3
CELLS
LEARNING OBJECTIVE 1: Explain how cells differ from one another.
Lecture Suggestions and Guidelines
1. Give an overview of the cellular basis of life.
2. Describe the relationship between the structure and the function of cells within the human body.
3. Compare the size, shape, and function of various cell types.
Application Question(s)
1. Cells vary tremendously in size. Ask students to cite specific examples of cells within the human body which
illustrate this phenomenon.
Answer: Some possible examples might include bacteria (2 micrometers in diameter) and nerve cells (1 meter
in length).
2. Cells vary dramatically in function. Ask students to cite specific examples of cells within the human body
which illustrate this phenomenon.
Answer: Examples might include white blood cells (immunity, phagocytosis) and nerve cells (nerve impulse
conduction).
Critical Thinking Issue(s)
1. How might the light microscope be limited as a tool for studying cellular structure and function?
Answer: Micrographs produced using the light microscope are typically two-dimensional.
The maximum effective magnification possible is about 1200x.
LEARNING OBJECTIVE 2: Describe the general characteristics of a composite cell.
Lecture Suggestions and Guidelines
1. Introduce the generalized anatomy of a composite cell.
2. Describe the three major parts of a cell: the nucleus, the cytoplasm, and the cell membrane.
3. Introduce a model of a composite cell and ask students to draw it based on their observations.
Application Question(s)
1. Although cells vary dramatically in size, shape, and function, what are some characteristics, which are common
to all cells?
Answer: In general, all cells have three main regions: the nucleus, which serves as the headquarters of the cell;
the cytoplasm, which contains organelles that carry out very specific functions; and a cell membrane, which
keeps the cell intact by providing a boundary and by allowing the transport of substances into and out of the
cell.
Critical Thinking Issue(s)
2. Consider the mature red blood cell. It is unlike many other cells in that it is anucleate, i.e., lacks a nucleus and
contains very few organelles. In fact, mature red blood cells lack mitochondria, the “powerhouses” of the cell.
Why is it important that red blood cells lack mitochondria?
Answer: Red blood cells manufacture adenosine triphosphate (ATP) by anaerobic mechanisms and thus do not
deplete the stores of oxygen they are transporting to other parts of the body.
LEARNING OBJECTIVE 3: Explain how the components of a cell’s membrane provide its functions.
Lecture Suggestions and Guidelines
1. Introduce the components of cell membrane structure: lipids and proteins with a small quantity of
carbohydrates.
10
2. Explain the phospholipid bilayer and introduce the terms hydrophilic and hydrophobic.
3. Discuss proteins, which provide the special functions of the membrane.
Application Question(s)
1. Ask students to discuss the varied roles of proteins, which are scattered throughout the lipid bilayer of the cell
membrane.
Answer: Some proteins serve as enzymes, some are receptors or binding sites, and still others are involved in
transport functions. When proteins combine with sugars to become glycoproteins, they can, among other
things, determine a patient’s blood type.
2. What causes Hyperkalemic Periodic Paralysis?
Answer: See textbook Clinical Application.
Critical Thinking Issue(s)
1.
Cell surface glycoproteins mark the cells of individuals as “self.’’ Give an example of an autoimmune disease
in which this system fails.
Answer: An example would be rheumatic heart disease in which a streptococcus infection migrates to heart
tissue. In an attempt to destroy the foreign bacteria, the immune system recognizes the patient’s healthy
tissue as foreign and proceeds to damage it.
LEARNING OBJECTIVE 4: Describe each kind of cytoplasmic organelle and explain its function.
Lecture Suggestions and Guidelines
1. Introduce the major organelles of a composite cell and describe the function of each.
2. A very effective learning tool is to ask the students to devise a chart, which lists all major organelles in one
column and the corresponding function in the next column. Reinforce this with flash cards. Write the name of
the organelle on one side, and briefly describe its function on the other side. Make a second set of flash cards
by reversing the front and back information.
Application Question(s)
1. Ask students to sketch their interpretation of how proteins, which are tagged for export, are ejected from the
cell.
Answer: Drawings will vary, but should illustrate that proteins accumulate in the Golgi apparatus, then the
membranous sacs swell until their swollen ends are pinched off to form secretory vesicles which migrate to the
cell membrane, where they finally fuse with the membrane, rupture, and eject the contents to the cell’s exterior.
Critical Thinking Issue(s)
1. Explain how proteins synthesized on the rough endoplasmic reticulum insert into the cell membrane.
Answer: They are incorporated into the membrane of the secretory vesicle. The vesicle fuses with the cell
membrane and any proteins in the vesicle membrane become membrane proteins of the cell. How these
proteins insert into the membrane depends on hydrophilic and hydrophobic regions in the protein.
LEARNING OBJECTIVE 5: Describe the cell nucleus and its parts.
Lecture Suggestions and Guidelines
1. Describe the cell nucleus, nuclear membrane, nucleoli, and chromatin.
2. Introduce DNA as the genetic material, which acts as a blueprint for the entire body.
Application Question(s)
1. How might DNA be compared to a strip of magnetic recording tape?
Answer: Its information is not useful until it is decoded. DNA requires not only a decoding mechanism, but
also a messenger in the form of RNA to specify the structure of proteins.
11
Critical Thinking Issue(s)
1. A wide variety of drugs are currently used in the treatment of cancer. Some of these drugs act to interrupt
cellular activity by disrupting the mitotic scaffolding, which appears during prophase. How might these drugs
be fatal to a cell?
Answer: The mitotic spindle provides a foundation for the attachment and movement of chromosomes during
cell division. If the scaffolding is disrupted, normal chromosome alignment cannot take place.
LEARNING OBJECTIVE 6: Explain how substances move into and out of cells.
Lecture Suggestions and Guidelines
1. Discuss active and passive transport.
2. Give examples of passive transport, including diffusion, osmosis, and filtration.
3. Give examples of active transport processes, including solute pumping, exocytosis/endocytosis, and
phagocytosis/pinocytosis.
Application Question(s)
1. Two patients visit the ER of a local hospital. Patient A appears to be edemic, with swollen hands and feet, due
to water retention. Patient B is dehydrated due to excessive exercise under a hot sun. What kind of IV therapy
might each patient be prescribed, i.e., a hypotonic solution or a hypertonic solution? Why?
Answer: Patient A would receive a hypertonic solution, for example, 5% NaCl. This will crenate the cells by
allowing water to leave the cell into the bloodstream to be excreted. Patient B would receive a hypotonic
solution, for example, 0.18% NaCl, to rehydrate the tissues, since this solution contains fewer solutes than are
inside the cell.
Critical Thinking Issue(s)
1. How might hemodialysis illustrate the concept of selective permeability?
Answer: The hemodialyzed patient’s blood is passed through selectively permeable membrane tubing, i.e.,
permeable only to certain substances. As the patient’s blood circulates through this tubing, potassium ion and
nitrogenous wastes diffuse out of the blood, while hydrogen ion buffers move from a bathing solution into the
blood.
LEARNING OBJECTIVE 7: Describe the cell cycle.
and
LEARNING OBJECTIVE 8: Explain how a cell divides.
Lecture Suggestions and Guidelines
1. Describe the events of cell division, including mitosis and cytokinesis.
2. Use the acronym PMATI - Please Memorize All This Information - as a tool to assist students in learning the
cell cycle phases - Prophase Metaphase Anaphase Telophase Interphase.
3. Distribute copies of textbook figure to students as a study aid.
Application Question(s)
1. Ask students to roughly sketch each phase of the cell cycle. Draw each phase on a separate index card and
shuffle them. Students should attempt to place the cell cycle phases in the correct order and describe at least
two major events, which occur in each of the phases.
Critical Thinking Issue(s)
1. Upon maturity, some groups of cells become amitotic. Give an example of this type of cell and explain why
injury or trauma to amitotic cells may have devastating effects.
Answer: Amitotic cells lose the ability to divide and reproduce similar or “like” cells. Examples would
include nerve cells or heart muscle cells. A patient who has experienced a severe heart attack will replace
healthy heart cells with scar tissue, which will inhibit the heart from working at full capacity.
12
2. Viruses lack the cellular machinery to reproduce themselves, yet manage to survive. Explain how this might
happen and describe a natural antimicrobial chemical, which aids humans in combating viral attacks.
Answer: Viruses damage the body by entering cells and confiscating the components necessary to reproduce
themselves. Virus-infected cells can secrete interferons which bind to healthy cell membranes and interfere with
viral replication.
LEARNING OBJECTIVE 9: Describe several controls of cell division.
Lecture Suggestions and Guidelines
1. Introduce the internal and external factors, which control cell reproduction.
2. Discuss the health consequences of the loss of cell reproduction and control.
Application Question(s)
1. Ask the students to bring to class information from a recent newspaper or magazine article or from an
experience with which they are familiar regarding cancer. Allow the students to highlight major points and
share their information with the class. Which cancers were classified as benign? Malignant? Which kinds of
cancer were reported to be the most common? Rarest? What kinds of treatment are currently available, etc.
Discuss and summarize these findings with the class.
Answer: N/A
Critical Thinking Issue(s)
1. Cloning has come to the forefront as an issue of major concern for both scientists and the general population.
Divide the classroom into groups of students. Group A represents scientists who support cloning in the interest
of furthering scientific knowledge and understanding. Group B represents a religious sector, which refutes the
value of such experimentation. Group C represents a capitalistic company that stands to profit greatly from the
“future of cloning.” Group D represents the federal government, which must decide to support or oppose future
cloning experimentation. Allow students to debate any relevant issues surrounding the controversy over
cloning.
Answer: N/A
SUGGESTIONS FOR ADDITIONAL READING
Barinaga, Marcia. April 23, 1993. Secrets of secretion revealed. Science, vol. 260. A fleet of vesicles carries out the
process of secretion, stopping at various organelles.
Bayley, Hagan. September 1997. Building Doors Into Cells. Scientific American.
Cech, Thomas R. October 21, 1994. Chromosome end games. Science, vol. 266. Once thought not to be very
important, we now know that telomeres are vital for chromosome stability and for control of cell division.
Ember, Lois R. November 28, 1994. The nicotine connection. Chemistry & Engineering News, vol. 72. Tobacco
addiction results from activity at cell surfaces.
Folkman, Judah. January 1995. Angiogenesis in cancer, vascular, rheumatoid, and other diseases. Nature Medicine,
vol. 1. Cell division not only causes a tumor to grow, but also provides a blood vessel supply to the abnormal
tissue.
Glover, David M., Cayetano Gonzales, and Jordan W. Raff. June 1993. The centrosome. Scientific American. A
complex interplay between microtubules and other cytoskeletal elements helps cells divide.
Hartwell, Leland H. and Michael B. Kastan. December 16, 1994. Cell cycle control and cancer. Science, vol. 266.
Cell biology is revealing how cancer arises.
Lewis, Ricki. March 1994. Gateway to the brain. BioScience, vol. 44. Understanding the function of the blood-brain
barrier leads to development of new drug delivery systems.
Lewis, Ricki. February 6, 1995. Cell death a lively area. The Scientist. At the cellular level, death is a part of life.
Marx, Jean. December 1994. Oncogenes reach a milestone. Science, vol 266. Understanding oncogenes has helped
explain cancer as well as normal cell function.
Miller, Robert V. January 1998. Bacterial Gene Swapping in Nature. Scientific American.
PantJ, Welly, and Veli Aebi. September 1993. The nuclear pore complex. Journal of Cell Biology, vol. 122, no. 5.
Nuclear pores are much more than simple holes.
13
Rodan, Eduardo R.S., Murase Tetsuma, and Qi-Xian Si. December 2, 1994. Exocytosis in spermatozoa in response
to progesterone and zona pellucida. Science, vol. 266. Exocytosis releases enzymes from a sperm’s tip that enable
it to penetrate the ovum.
Spudich, James. December 8, 1994. How molecular motors work. Nature, vol. 370. Molecules that move keep a cell
active.
Thompson, Dick. September 28, 1992. The glue of life. Time. People missing adhesion molecules live dangerously.
Valle, David, and Jutta Gartner. February 25, 1993. Penetrating the peroxisome. Nature, vol. 361.
Adrenoleukodystrophy is caused by a missing or abnormal peroxisomal protein-but not the one researchers had
suspected.
14