Download Lesson 7A Specialized Cells

Lesson 7A
Specialized Cells, Stem Cells & Cellular Differentiation
Learning Goals
• I can explain the concept of cell differentiation
and cell specialization.
• I can explain how the cell structure relates to the
functions of the specialized cells.
• I can explain the different types of stem cells.
• I can explain the importance of stem cell
research and the ethical issues related to stem
cell applications.
Specialized Cells
• Specialized cells have special shapes and structures
that allow them to do specific functions (jobs)
How do cells become specialized?
• Cell differentiation: A cell
becomes specialized to
perform a specific job
• Is directed by the genetic
information (in DNA) inside
the cell
• Occurs in during early
development of living
organisms
Cell Differentiation
What is cell specialization?
• Cell specialization: Cells change from similar
cells into cells that have specific functions
within a multi-cellular organism
• E.g. A stem cell becomes a red blood cell that carries
oxygen.
What is the difference between cell
specialization and cell differentiation?
Cell specialization refers to the functions that certain cells
have, such as red blood cells are specialized to carry oxygen.
Cell differentiation is the process that a cell undergoes to
get that specialization.
We would say stem cells undergo cell differentiation to
become red blood cells.
What is a specialized cell?
A specialized cell: A cell that
•comes from a non-specialized cell (stem cell)
•look different from each other: smooth surface
(red blood cells); long and thin with many
branches (nerve cells)
A Specialized Cell: A cell that • is different internally (inside cell)
o muscle cells that use a lot of energy – have
more mitochondria
o cells in intestine that produce mucus – have
more Golgi bodies
o fat cells that store fat molecules – have a
large vacuole
A Specialized Cell:
specific job
• carry out a ______________________
o bone cells store calcium and build
new bone
o skeletal muscle cells contract to
allow movement
o fat cells store energy in the form of
fat
o nerve cells conduct electrical
signals or coordinate activities
o hair cells in the inner ear detect
sound vibrations
o red blood cells deliver oxygen and
remove carbon dioxide
o skin cells cover the body and
reduce water loss
Where do the specialized cells come
from??
Stem cell
What are Stem Cells?
Non-specialized cells
• Stem Cells: _______________________________
that can produce various specialized cells
Human Embryonic Stem Cells
Coloured scanning electron micrograph of human embryonic stem cells (Image: Miodrag Stojkovic/Science Photo Library)
What are Stem Cells?
• Can divide to
produce copies of
themselves through
mitosis and
cytokinesis
• Daughter cells can
develop into
different types of
cells based on
which genes are
switched on
What are Stem Cells?
• Occurred in groups that
differentiate into
different tissues layers
(epithelial, muscle, and
nerve tissues)
• Can be found in various
parts of the human
body at every stage of
development from
embryo to adult
Stomach stem cells labelled with green fluorescent protein
3 Types of Human Stem Cells
Within 24 hrs
Within 4‐5 Embryonic Stem days
Cells 1. Totipotent Stem Cells 2. Pluripotent Stem Cells Form any type of tissue
After that …
3. Adult Stem Cells Form specific types of tissue
Form many types of tissue
3 Types of Stem Cells:
Embryonic Stem Cells
•Found in very young embryos (< 1 week old)
2 Types of Embryonic Stem Cells:
1) Totipotent stem cells (early embryo – within 24 hours)
any kindof cell
•Can become _______________
2) Pluripotent stem cells (embryo – 4 to 5 days)
many kinds cells, but not all types
•Can become __________________of
of cells
3 Types of Stem Cells:
2. Adult Stem Cells
(Tissue stem cells)
•Found in the late
development of the fetus
or after birth
•Exist within specialized
tissue or organ
•Only able to differentiate
into certain type of cells
•Purpose: to maintain and
repair the tissue in which
they are found
Adult stem cells
in bone marrow
Adult Stem Cells
(Tissue stem cells)
• can produce all of the cell types associated with the tissues
from which they
originate
• E.g. In heart – produce cardiac muscle cells
• maintain and repair
the body’s tissues in which they are found.
Why are Stem Cells Useful?
repair
replace damaged
• To ______________
and ______________
human tissue
treat
cure
• To ______________
and ______________
disease and
injuries
How might Stem Cells be used to develop treatments for diseases?
• Natural processes cannot replace most body’s
specialized cells if they are seriously damaged
or diseased.
• Transplantation of healthy organs from donors
has posed high risks
• Treat patients by transplanting specialized
cells that are grown from stem cells in the lab.
Limb Amputations
Spinal Cord Injuries
Disorders in Brain
Heart Disease
Burns
Diabetes
Potential Uses of Stem Cells
The Medical Potential of Stem Cells:
Adult Stem Cell Transplantation
• Bone marrow has
adult stem cells that
can differentiate into
blood cells → bone
marrow transplants
are often use to treat
cancers that affect
blood cells
Bone marrow transplant: A procedure to replace damaged or destroyed bone marrow with healthy bone marrow stem cells; to replace replenish bone marrow that has been destroyed by drug or radiation therapy for cancer (leukemia).
stem cells treat diseases like cancer
The Medical Potential of Stem Cells:
Adult Stem Cell Transplantation
Umbilical cord blood has a high concentration of the adult stem cells → treat childhood leukemia
(cancer in bone marrow)
Issue with Embryonic Stem Cells:
Where do the embryonic stem cells come from?
1. From human embryo left over from fertility
treatments
2. From cloned human embryos developed in
the lab
Human Embryos from In Vitro Fertilization (outside the body)
Issue with Embryonic Stem Cells
•The use of stem cells from human embryos may
not be acceptable, so adult stem cells offer an
alternative that has less ethical and moral
complications.
Ethical Issues in Stem Cell Research
Ethical
________________
issues: Consider the potential moral
outcomes of stem cell technologies
The controversy centered on the moral implications of
destroying human embryos.
•Do embryonic stem cells represent a human life?
When does life begin – at fertilization, in the womb, or
at birth?
•Is a human embryo the same as a human child?
•Does a human embryo have any rights?
•Might the killing of a single embryo be justified if it
provides a cure for a countless number of patients?
•Should frozen embryos created through in vitro
fertilization be used to create stem cells? Why or why
not?
Legal Issues in Stem Cell Research
Legal
____________
issues: Require researchers and the
public to help policymakers decide whether and
how stem cell technologies should be
regulated by the government
•Should there be laws to regulate stem cell research?
•If so, what would they look like? For example, how
would you regulate research using different types of
stem cells, such as embryonic, fetal or adult stem
cells? What about embryonic stem cells created using
cloning technologies?
Social Issues in Stem Cell Research
Social issues: The impact of stem cell
__________
technologies on society as a whole
•Will the medical benefits of stem cell research be
available to all people?
•With the high costs of treatment and research will
there be equality of access?