Lesson Overview
Regulating the Cell Cycle
Lesson Overview
10.3 Regulating
the Cell Cycle
Lesson Overview
Regulating the Cell Cycle
The Cell Cycle
The 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 are a family of proteins that regulate the timing of
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 are proteins that respond to events
inside a cell. They allow the cell cycle to proceed only once
certain processes have happened inside the cell.
External regulators are proteins that respond to events
outside the cell. They direct cells to speed up or slow down
the cell cycle.
Growth factors are external regulators that stimulate the
growth and division of cells. They are important during
embryonic development and wound healing.
Lesson Overview
Regulating the Cell Cycle
Lesson Overview
Regulating the Cell Cycle
HeLa Cells
The Story of Henrietta Lacks
http://www.youtube.com/watch?v=0gF8bCE4wqA&feature=related
Lesson Overview
Regulating the Cell Cycle
Apoptosis
Apoptosis is a process of programmed cell death.
Apoptosis plays a role in development by 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 is a disorder in which body cells lose the
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
A benign tumor is noncancerous. It
does not spread to surrounding
healthy tissue.
A malignant tumor is cancerous. It
invades and destroys surrounding
healthy tissue and can spread to
other parts of the body. The spread
of cancer cells is called metastasis.
Cancer cells absorb nutrients needed
by other cells, block nerve
connections, and prevent organs from
functioning.
Lesson Overview
Regulating the Cell Cycle
What Causes Cancer?
Cancers are caused by defects in genes that regulate cell
growth and division.
Some sources of gene defects are smoking tobacco,
radiation exposure, defective genes, and viral infection.
A damaged or defective p53 gene is common in cancer
cells. It 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
From One Cell to Many
All organisms start life as just one
cell.
Most multicellular organisms pass
through an early stage of
development called an embryo,
which gradually develops into an
adult organism.
During development, an organism’s
cells become more differentiated
and specialized for particular
functions.
Lesson Overview
Regulating the Cell Cycle
Defining Differentiation
The process by which cells become specialized is known as
differentiation.
During development, cells differentiate into many different types
and become specialized to perform certain tasks.
Lesson Overview
Regulating the Cell Cycle
Human Development
Biologists say that such a cell is totipotent, literally able to do
everything, to form all the tissues of the body. (a fertilized egg)
After about four days of development, 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 cells of the inner cell mass are said to be pluripotent, which
means that 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 are found in the
inner cells mass of the early embryo.
Embryonic stem cells are pluripotent.
Researchers have grown stem cells
isolated from human embryos in
culture. Their experiments confirmed
that embryonic stem cells have the
capacity to produce most cell types in
the human body.
Lesson Overview
Regulating the Cell Cycle
Adult Stem Cells
Adult organisms contain some types
of stem cells. Adult stem cells are
multipotent. They can produce many
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 harvesting, or
gathering, embryonic stem cells cause
destruction of the embryo.
Government funding of embryonic stem cell
research is an important political issue.
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