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Lesson Overview
Regulating the Cell Cycle
Lesson Overview
10.1 Cell Growth, Division,
and Reproduction
Lesson Overview
Regulating the Cell Cycle
Limits to Cell Size
• What are some of the difficulties a cell faces as
it increases in size?
• The larger a cell becomes, the more
demands the cell places on its DNA.
• A larger cell is less efficient in
moving materials
across its cell membrane.
Lesson Overview
Regulating the Cell Cycle
Information “Overload”
Living cells store critical information in DNA.
As a cell grows, more information is needed.
If a cell were to grow without limit, an
“information crisis” would occur.
Lesson Overview
Regulating the Cell Cycle
Information “Overload”
Compare a cell to a growing
town. The town library has a
limited number of books. As the
town grows, these
limited number of books are in
greater demand,
which limits access.
A growing cell makes greater
demands on its genetic “library.” If
the cell gets too big, the DNA
would not be able to serve the
needs of the growing cell.
Lesson Overview
Regulating the Cell Cycle
Exchanging Materials
• The rate at which this exchange takes place
depends on the cell’s surface area.
• The rate at which materials are used up
depends on the cell’s volume.
• The ratio of surface area to volume
is key to understanding why cells must
divide as they grow.
Lesson Overview
Regulating the Cell Cycle
Ratio of Surface Area to Volume
-Imagine a cell shaped like a cube.
-As the length increases,
its volume increases faster than its surface area.
• The SA:V ratio decreases.
Lesson Overview
Regulating the Cell Cycle
Traffic Problems
• Compare to a town – As the
town grows, it becomes
more difficult
to move information and
goods.
Similarly, a cell that continues to
grow would experience
“traffic” problems.
If the cell got too large, it would be
more difficult to get oxygen and
nutrients in and waste out.
Lesson Overview
Regulating the Cell Cycle
Division of the Cell
Before a cell grows too large, it divides into
two new “daughter” cells in a process called
cell division.
Cell division keeps a stable SA:V ratio.
Lesson Overview
Regulating the Cell Cycle
Cell Division and Reproduction
How do asexual and sexual reproduction
compare?
-Asexual reproduction – Produce genetically
identical offspring from
a single parent
Lesson Overview
Regulating the Cell Cycle
-Sexual reproduction – Offspring
inherit some of their genetic information
from each parent.
Lesson Overview
Regulating the Cell Cycle
Asexual Reproduction
• Advantages:
• Quick, produces many.
• Disadvantages
• Genetically identical / no diversity
Lesson Overview
Regulating the Cell Cycle
Sexual Reproduction
• Advantages:
• Genetic diversity
• Disadvantages:
• Time, less produced
Lesson Overview
Regulating the Cell Cycle
Review
1. What are two reasons a large cell is problematic?
-Too much demand on DNA
-Less efficient at moving materials
2. What ratio decreases as a cell gets larger?
-SA:V
Lesson Overview
Regulating the Cell Cycle
Review
3. How many parents are involved in asexual reprod?
-One
4. How do offspring compare to the parent in A.R.?
-They are identical
5. How many parents are involved in sexual reprod?
-Two
6. How do offspring compare to the parent in S.R.?
-Mix of genes
Lesson Overview
Regulating the Cell Cycle
Review
7. Fill in the information below:
-Sexual Reproduction
-Advantage:
-Genetic Diversity
-Disadvantage
-Takes time
Lesson Overview
Regulating the Cell Cycle
Review
8. Fill in the information below:
-Asexual Reproduction
-Advantage:
-Quick and many produced
-Disadvantage
-No diversity
Lesson Overview
Regulating the Cell Cycle
Lesson Overview
10.2 The Process
of Cell Division
Lesson Overview
Regulating the Cell Cycle
Prokaryotes
• Cells carry genetic information in packages of
DNA called chromosomes.
• Most prokaryotes have
only one circular stand of DNA
Lesson Overview
Regulating the Cell Cycle
Eukaryotes
• In eukaryotes, the DNA is wound around a
histone protein
• Together make a nucleosome.
• Chromosomes make the precise
separation of DNA during cell division.
Lesson Overview
Regulating the Cell Cycle
DNA is condensed to form
chromatin, which condense even
more to form chromatids, which
make up chromosomes.
Lesson Overview
Regulating the Cell Cycle
The Prokaryotic Cell Cycle
• In prokaryotes, when DNA replication is
complete, cells go through a process of cell
division known as
binary fission.
• Binary fission = asexual reprod. = Identical offspring
Lesson Overview
Regulating the Cell Cycle
The Eukaryotic Cell Cycle
Interphase
• The time
between
cell divisions.
• Period of growth that
consists of the
G1, S, and G2
phases.
Lesson Overview
Regulating the Cell Cycle
1.
4.
3.
2.
Lesson Overview
Regulating the Cell Cycle
Interphase
• G1 phase – cells get larger
and make new materials.
• S (synthesis) phase –
new DNA is
synthesized
• G2 phase - prepare
for cell division
Lesson Overview
Regulating the Cell Cycle
M Phase: Cell Division
• In eukaryotes, cell division
occurs in two stages:
mitosis and cytokinesis.
• Mitosis - division
of the cell nucleus.
• Cytokinesis –
division of the
cytoplasm.
Lesson Overview
Regulating the Cell Cycle
Mitosis
Cytokinesis
Lesson Overview
Regulating the Cell Cycle
Review
1. How many strands of DNA do prokaryotes have?
- One
2. Nucleosomes are made up of what two things?
-DNA wound around a histone protein
3. Organize “chromatid, chromosomes, DNA, and
chromatin” in order from smallest to largest.
-DNA, chromatin, chromatid, chromosome
4. Prokaryotes go thorugh a process of asex. reprod.
called…
- Binary Fission
Lesson Overview
Regulating the Cell Cycle
Review
5. What are the four phases of the cycle cycle?
- G1, S, G2, M
6. G1, S, and G2 phases are all part of what?
-Interphase
7. What two phases make up the M Phase?
- Mitosis and Cytokinesis
8. What’s the difference between mitosis and cytok.?
-Mitosis – Nucleus splits
-Cytokinesis – Cytoplasm splits
Lesson Overview
Regulating the Cell Cycle
Important Cell Structures
Involved in Mitosis
Chromatid –
each strand of a duplicated
chromosome
Centromere –
the area where chromatids
are joined
Lesson Overview
Regulating the Cell Cycle
Important Cell Structures Involved in
Mitosis
Centrioles –
organize the spindle
Spindle –
microtubules that
separate the
chromatids
Lesson Overview
Regulating the Cell Cycle
Four Steps of Mitosis:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
Lesson Overview
Regulating the Cell Cycle
1. Prophase
• Prophase
-the first phase of mitosis
-chromosomes condense and
becomes visible.
• Centrioles move
to opposite sides of nucleus and
organize the spindle.
• The nucleolus
disappears and
nuclear envelope breaks down.
Lesson Overview
Regulating the Cell Cycle
2. Metaphase
Metaphase,
-second phase of mitosis
-centromeres line up across
the center.
A spindle fiber from each pole
connects to the
centromere.
Lesson Overview
Regulating the Cell Cycle
3. Anaphase
• Anaphase
-third phase of mitosis
-centromeres are
pulled apart
and each chromatid becomes
a separate chromosome.
• The chromosomes move
towards the poles.
Lesson Overview
Regulating the Cell Cycle
4. Telophase
• Telophase,
-fourth and final phase of mitosis
-chromosomes unwind into
chromatin.
• Nuclear envelope
re-forms around
chromosomes.
• Spindle breaks apart, and the
nucleolus becomes visible in each
daughter nucleus.
Lesson Overview
Regulating the Cell Cycle
Cytokinesis
• Not part of mitosis!
• Part of the M Phase
• Cytokinesis completes the process of cell
division – it splits one cell into two.
Lesson Overview
Regulating the Cell Cycle
Cytokinesis – Animals vs. Plants
• Animals
• Cell membrane is drawn in until the cytoplasm
is pinched into two equal parts.
Lesson Overview
Regulating the Cell Cycle
Cytokinesis – Animals vs. Plants
• Plants
• In plants, the cell wall prevents pinching.
• Instead, a cell plate forms between the
divided nuclei that develops into cell membranes.
• A cell wall then forms in between the two new
membranes.
Lesson Overview
Regulating the Cell Cycle
The Stages of the Cell Cycle
Lesson Overview
Regulating the Cell Cycle
Review
1. The chromatids are joined at the
-Centromere
2. The spindle is organized by what structures?
- Centrioles
3. Think of a mnemonic for the 4 stages of mitosis.
-Please Make A Take
4. Cytokinesis is not part of…
-Mitosis
Lesson Overview
Regulating the Cell Cycle
Review
5. Which part of mitosis do chromatids line in the middle?
-Metaphase
6. What part does the chromosomes become visible?
-Prophase
7. What part does the nuclear envelope start to reform?
-Telophase
8. What part pulls the sister chromatid apart?
-Anaphase
Lesson Overview
Regulating the Cell Cycle
Lesson Overview
10.3 Regulating
the Cell Cycle
Lesson Overview
Regulating the Cell Cycle
The Cell Cycle
• Controls on cell growth and division can be
turned on and off.
• For example, when an injury such as a broken bone
occurs, cells are stimulated to divide rapidly and
start the healing process. The rate of cell division
slows when the healing process nears completion.
Lesson Overview
Regulating the Cell Cycle
The Discovery of Cyclins
• Cyclins - proteins that regulate the cell cycle
in eukaryotic cells.
• This graph shows how cyclin levels change
throughout the cell cycle in fertilized clam eggs.
Lesson Overview
Regulating the Cell Cycle
Regulatory Proteins
• Internal regulators - respond to events
inside a cell.
• Allow the cell cycle to proceed only once certain
processes have happened.
• External regulators - respond to events
outside the cell.
• They direct cells to speed up or slow down the cell
cycle.
• Ex - Growth factors –
Important during embryonic development and wound
healing.
Lesson Overview
Regulating the Cell Cycle
Apoptosis
• Apoptosis - programmed cell death.
• Plays role in shaping the structure
of tissues and organs in plants and animals.
• For example, the foot of a mouse is shaped the way it is
partly because the toes undergo apoptosis during tissue
development.
Lesson Overview
Regulating the Cell Cycle
Cancer and the Cell Cycle
• Cancer - disorder in which body cells
lose ability to control cell growth.
• Cancer cells divide uncontrollably to form a
mass of cells called a tumor.
Lesson Overview
Regulating the Cell Cycle
Cancer and the Cell Cycle
• Benign tumor = noncancerous.
Does not spread to surrounding
healthy tissue.
• Malignant tumor = cancerous.
It spread and destroys surrounding
healthy tissue.
Lesson Overview
Regulating the Cell Cycle
What Causes Cancer?
• Caused by defects in genes
that regulate cell growth and division.
• Causes include smoking tobacco, radiation
exposure, defective genes, and viral infection.
• A damaged p53 gene is common in cancer cells.
• Causes cells to lose the information needed to
respond to growth signals.
Lesson Overview
Regulating the Cell Cycle
Treatments for Cancer
• Some localized tumors can be removed by
surgery.
• Many tumors can be treated with targeted
radiation.
• Chemotherapy is the
use of compounds that kill or slow the growth of
cancer cells.
• Cancer Warrior PBS
Lesson Overview
Regulating the Cell Cycle
Review
1. When might cell growth be stimulated?
- Injury, growth, etc.
2. Which protein regulates the cell cycle in eukar.?
- Cyclin
3. Which regulator would prevent anaphase from
happening before prophase?
- Internal regulators
4. What is an example of an external regulator?
-Growth factor
Lesson Overview
Regulating the Cell Cycle
Review
5. What is apoptosis?
- Programmed cell death
6. During cancer, cells lose the ability to…
-Control cell growth
7. What type of tumor is noncancerous?
- Benign
8. Which damaged gene is commonly found in cancer
cells?
- p 53
Lesson Overview
Regulating the Cell Cycle
10.4 Cell
Differentiation
Lesson Overview
Regulating the Cell Cycle
From One Cell to Many
• All organisms start a single cell.
• Embryo - Early stage of
development
• During development, an organism’s
cells become
differentiated
and specialized
for particular functions.
Lesson Overview
Regulating the Cell Cycle
Defining Differentiation
• Differentiation - process by which cells become
specialized.
• During development, cells differentiate into many
different types and become specialized to perform
certain tasks.
Lesson Overview
Regulating the Cell Cycle
Human Development
• Totipotent - able to do everything,
to form all the tissues of the body (a fertilized egg)
• After a few days, a human embryo forms into a
blastocyst, a hollow ball of cells
with a cluster of cells inside known as the inner cell
mass.
• The inner cell mass are pluripotent –
they are capable of developing into many, but not
all, of the body's cell types.
Lesson Overview
Regulating the Cell Cycle
Stem Cells
Stem cells are unspecialized cells from
which differentiated cells develop.
Lesson Overview
Regulating the Cell Cycle
Embryonic Stem Cells
• Embryonic stem cells –
found in the inner cells mass.
• Embryonic stem cell are
pluripotent.
Lesson Overview
Regulating the Cell Cycle
Adult Stem Cells
• Adult organisms contain
certain stem cells.
• Adult stem cells are
multipotent –
produce a few types of
differentiated cells.
• Adult stem cells of a given
organ or tissue typically
produce only the types of
cells that are unique to that
tissue.
Lesson Overview
Regulating the Cell Cycle
Potential Benefits
• Stem cell research may lead to new ways to
repair the cellular damage
that results from heart attack, stroke, and spinal
cord injuries.
Lesson Overview
Regulating the Cell Cycle
Ethical Issues
• Most techniques for gathering
embryonic stem cells
destroy the embryo.
• Groups seeking to
protect embryos
oppose such research as
unethical. Other groups
support this research as
essential to saving
human lives and so view it as
unethical to restrict the
research.
• BBC Documentary
Lesson Overview
Regulating the Cell Cycle
Review
1. What is the earliest stage of development called?
- Embryo
2. The process by which cells become specialized is…
- Differentiation
3. What is totipotent, pluripotent, and multipotent?
-Totipotent – can become all cells
-Pluripotent – can become most cells
-Multipotent – can become few cells
Lesson Overview
Regulating the Cell Cycle
Review
4. Stem cells are
cells.
-Undifferentiated
5. Adult stem cells produce cells that are…
-Unique to that tissue
6. Why is stem cell research important?
-Repair damaged cells and save lives
7. Why is stem cell research controversial?
-Save embryos vs. save lives