CHAPTER 9 –
CELLULAR
REPRODUCTION
CHAPTER 9.1 – CELLULAR
GROWTH
Essential Question:
• Why is it beneficial for cells to remain small?
Main Idea
• Cells grow until they reach their size limit, then they either stop growing or divide.
Vocabulary
• Cell Cycle
• Interphase
• Mitosis
• Cytokinesis
• Chromosome
• Chromatin
CELL SIZE LIMITATIONS
•
Most cells are smaller than a period at the end of a sentence.
•
There are two reasons cells divide rather that continue to grow.
•
The larger the cell becomes, the more demands the cell places on it
DNA.
•
The larger the cell becomes, the more trouble the cell has moving
nutrients and wastes across the cell membrane.
RATIO OF SURFACE AREA TO
VOLUME
•
The key factor that limits the size of a cell is the ratio of its surface
area to volume.
•
The surface area refers to the area covered by the plasma membrane.
•
The volume refers to the space taken by the inner contents of the cell,
including the organelles in the cytoplasm and the nucleus.
RATIO OF SURFACE AREA TO
VOLUME
•
As a cell grows in size, its volume increases faster than its surface
area.
•
This means the cell might have trouble supplying and transporting
nutrients and expelling enough waste products.
•
By remaining small, cells can sustain themselves more easily.
CELL CYCLE
•
Once a cell reaches its size limit, it will either stop growing or divide.
•
Most cells divide. Nerve and muscle cells do not divide.
•
Cell division also is the way the cell reproduces so that you grow and
heal certain injuries.
•
Cells reproduce by a cycle of growing and dividing called the cell
cycle
CELL CYCLE
•
3 main stages……..
•
•
•
Interphase – cell grows, carries out certain cellular functions, replicates its DNA
[3 substages]
Mitosis – cell’s nucleus and nuclear material, DNA, divide [4 substages]
Cytokinesis – cytoplasm divides
STAGES OF INTERPHASE
•
G1 stage (normal cell growth) has the longest duration.
•
G1 - 1st stage, a cell is growing, carrying out normal cell functions,
and preparing to replicate or copy DNA
•
•
S - 2nd stage, cell copies its DNA in preparation for cell division
•
•
The cell is growing, carrying out normal cell functions, and preparing to replicate
DNA.
The cell copies its DNA in preparation for cell division.
Chromosomes contain the genetic material that is passed from one
generation to the next.
STAGES OF INTERPHASE
•
Chromatin is the relaxed form of DNA in a cell’s nucleus.
•
Chromatin condenses or tightens to form chromosomes.
•
G2 - 3rd stage, Cell prepares for the division of its nucleus.
•
•
•
The cell makes sure everything is ready for mitosis.
The cell prepares for the division of its nucleus.
A cell spends the majority of its lifetime in interphase.
9.1 SECTION SUMMARY
•
Cells grow until they reach their size limit, then they either stop
growing or divide.
•
The ratio of surface area to volume describes the size of the plasma
membrane relative to the volume of the cell.
•
Cells are limited in size, with most cells having a diameter of less than
100 µm.
•
The cell cycle is the process of cellular reproduction.
•
A cell spends the majority of its lifetime in interphase.
9.1 SECTION ASSESSMENT
1.
Relate cell size to cell functions, and explain why cell size is limited.
2.
Summarize the primary stages of the cell cycle.
3.
Describe what happens to DNA during the S stage of interphase.
4.
Create a diagram of the stages of the cell cycle and describe what
happens in each.
5.
Hypothesize what the result would be if a large cell managed to
divide, despite the fact that it had grown beyond an optimum size.
6.
Math in Biology. If a cube representing a cell is 100 µm on a side,
calculate the surface area-to-volume ratio, and explain why this is or
is not a good size for a cell.
9.2 – MITOSIS AND
CYTOKINESIS
9.2 – MITOSIS AND CYTOKINESIS
Main Idea
• Eukaryotic cells reproduce by mitosis, the process of nuclear division, and
cytokinesis, the process of cytoplasmic division.
Vocabulary
• Sister Chromatid
• Centromere
• Spindle Apparatus
• Metaphase
• Anaphase
• Telophase
9.2 SECTION SUMMARY
•
Eukaryotic cells reproduce by mitosis, the process of nuclear division,
and cytokinesis, the process of cytoplasm division.
•
Mitosis is the process by which the duplicated DNA is divided.
•
The stages of mitosis include prophase, metaphase, anaphase, and
telophase.
•
Cytokinesis is the process of cytoplasm division that results in
genetically identical daughter cells.
PHASES OF MITOSIS - PROPHASE
•
1st phase - longest
•
Chromatin tightens into chromosomes that are X-shaped and become
visible.
•
Centrioles separate and move to opposite poles of the cell.
•
Nuclear membrane disintegrates.
•
Nucleolus disappears.
•
Mitotic spindle begins to form between the poles.
PROPHASE
•
Spindle apparatus is made of spindle fibers, centrioles, and aster
fibers.
•
The spindle apparatus is important in organizing and moving
chromosomes before cell division.
•
Plant cells do not have centrioles.
BY THE END OF PROPHASE, THE
FOLLOWING HAS OCCURRED
•
By the end of prophase, the following has occurred:
•
Nuclear envelope seems to disappear.
•
Spindle fibers attach to sister chromatids on both sides of the
centromere.
METAPHASE
•
2nd phase - shortest
•
Sister chromatids are pulled along the spindle apparatus to center of
cell and line up in the middle.
•
Tension of spindle fibers pulls them along.
ANAPHASE
•
3rd phase
•
The centromeres that join the sister chromatids split.
•
The sister chromosomes become individual chromosomes.
•
The two sets of chromosomes move apart to opposite poles.
TELOPHASE
•
4th phase - last phase
•
Chromosomes gather at opposite ends of the cell and lose their
shape.
•
Two new nuclear envelopes form.
•
Nucleoli reappear.
•
Spindle apparatus comes apart.
CYTOKINESIS
•
Cytokinesis usually happens at the same time as telophase.
•
The cell membrane is pulled inward until the cytoplasm is pinched into
two nearly equal parts.
•
Results are two cells, with identical nuclei.
•
In plant cells, a cell plate forms that later becomes cell wall to divide
the cells.
9.2 SECTION SUMMARY
•
Eukaryotic cells reproduce by mitosis, the process of nuclear division,
and cytokinesis, the process of cytoplasm division.
•
Mitosis is the process by which the duplicated DNA is divided.
•
The stages of mitosis include prophase, metaphase, anaphase, and
telophase.
•
Cytokinesis is the process of cytoplasm division that results in
genetically identical daughter cells.
9.2 SECTION ASSESSMENT
Explain why mitosis alone does not produce daughter cells.
2. Describe the events of each stage of mitosis.
3. Diagram and label a chromosome in prophase.
1.
Identify the stage of mitosis in which a cell spends the most time.
5. Contrast cytokinesis in a plant cell and an animal cell.
6. Hypothesize what might happen if a drug that stopped microtubule
movement but did not affect cytokinesis was applied to a cell.
7. Math in Biology. If a plant cell completes the cell cycle in 24 hours,
how many cells will be produced in a week?
4.
9.3 – CELL CYCLE
REGULATION
9.3 – CELL CYCLE REGULATION
Main Idea
• The normal cell cycle is regulated by cyclin proteins.
Vocabulary
• cyclin
• cyclin-dependent kinase
• cancer
• carcinogen
• apoptosis
• stem cell
•
9.3 SECTION SUMMARY
•
The normal cell cycle is regulated by cyclin proteins.
• The normal cell cycle is regulated by cyclin proteins.
• The cell cycle of eukaryotic cells is regulated by cyclins.
•
Checkpoints occur during most of the stages of the cell cycle to
ensure that the cell divides accurately.
• Cancer is the uncontrolled growth and division of cells.
• Apoptosis is programmed cell death.
• Stem cells are unspecialized cells that can develop into specialized
cells with the proper signals.
CYCLINS
•
In a multicellular organism, cell growth and cell division are carefully
controlled.
•
When an injury such as a cut in the skin occurs, cells at the edge of
the cut divide rapidly.
•
When the healing process is nearly complete, the rate of cell division
slows and then returns to normal.
CYCLINS
•
When cells come into contact with one another, molecules on their
surface signal them to stop growing.
•
Cyclins, a group of proteins, regulate the timing of the cell cycle in
eukaryotic cells.
•
Cyclins are one group of proteins involved in cell cycle regulation.
•
Other proteins, called regulatory proteins, regulate the cell cycle in
different ways.
CANCER
•
Controls on cell growth can be turned on and off by the body.
•
Cancer is a disorder in which some of the body’s cells lose the ability
to control growth.
•
Cancer cells do not respond to the signals that control the growth of
most cells.
•
As a result, cancer cells divide uncontrollably.
CANCER
•
Cancer cells reproduce rapidly because they spend less time in
interphase.
•
Cancer cells do not stop growing when they touch other cells.
•
They continue to grow and divide until their supply of nutrients is used
up.
CANCER CAN BE CAUSED BY …
•
Changes that occur in the regulation of cell growth and division of
cancer cells are due to mutations or changes in segments of DNA.
•
The changes can damage the control of the proteins that regulate the
cell cycle.
•
The genetic change or damage can often be repaired by various
repair systems
•
If repair systems fail, cancer can result.
CARCINOGENS
•
Various environmental factors can affect the occurrence of cancer
cells.
•
Substances that are known to cause cancer are called carcinogens.
•
Examples: cigarettes, asbestos, X rays, the Sun’s ultraviolet rays
APOPTOSIS
•
Apoptosis is programmed cell death.
•
Cells going through apoptosis actually shrink and shrivel in a
controlled process.
•
Example: When hands and feet begin to develop, there are cells
between fingers and toes that look like webbing.
•
The webbing is not present in the mature organism.
STEM CELLS
•
Most cells in a multicellular organism are designed for a specialized
function.
•
Stem cells are unspecialized cells that can develop into specialized
cells when under the right conditions.
•
Two basic types of stem cells:
•
Embryonic- After a sperm sterilizes an egg, the resulting mass of cells
divides until there are about 100-150 cells.
STEM CELLS
•
Adult- Found in various tissues in the body and might be used to
maintain and repair the same kind of tissue where they are found.
•
Researchers think certain kinds of adult stem cells might be able to
develop into different kinds of cells for treatment of disease and
conditions.
9.3 SECTION SUMMARY
•
The normal cell cycle is regulated by cyclin proteins.
• The normal cell cycle is regulated by cyclin proteins.
• The cell cycle of eukaryotic cells is regulated by cyclins.
•
Checkpoints occur during most of the stages of the cell cycle to
ensure that the cell divides accurately.
• Cancer is the uncontrolled growth and division of cells.
• Apoptosis is programmed cell death.
• Stem cells are unspecialized cells that can develop into specialized
cells with the proper signals.
9.3 SECTION ASSESSMENT
1.
Describe how cyclins control the cell cycle.
2.
Explain how the cancer cell cycle is different from a normal cell cycle.
3.
Identify three carcinogens.
4.
Contrast apoptosis and cancer.
5.
Describe a possible application for stem cells.
6.
Explain the difference between embryonic stem cells and adult stem cells.
7.
Hypothesize what might happen if apoptosis did not occur in cells that
have significant DNA damage.
8.
Writing in Biology. Write a public service announcement about
carcinogens. Choose a specific type of cancer, and write about the
carcinogens linked to it.