5.5 Multicellular Life
Chapter 5 Cell Growth and Division
Mr. Shilala
DAHS
KEY CONCEPT
Cells work together to carry out complex
functions.
Multicellular organisms depend on
interactions among different cell types.
leaf
stem
vascular
tissue
CELL
TISSUE
ORGAN
lateral
roots
primary
root
shoot system
SYSTEMS
root system
• Tissues are groups of cells that
perform a similar function.
• Organs are groups of tissues that
perform a specific or related function.
• Organ systems are groups of organs
that carry out similar functions.
• Organ systems help an organism
maintain homeostasis
– Example Plants need to maintain a specific
water level or they can wilt and die
– Absorb water through roots and expel through
Stomata in leaves
What label should replace
the X in the diagram
above?
Specialized cells perform specific functions.
• Cells develop into their mature forms through the process
of cell differentiation.
• Most cells contain a full set of DNA.
• However, a cell differentiates among the genes and only
uses certain ones
– Example - Making a specific meal
• DNA = a cookbook
• Different genes = different ingredients
• Different cells = different recipes
Outer: skin cells
Middle: bone cells
Inner: intestines
• A cell’s location in an
embryo helps determine how
it will differentiate.
• Example animal cell
– Many rapid divisions after
fertilization
– Cells migrate to specific region
– Begin to differentiate
– Resemble hollow ball
Outer: skin cells
Middle: bone cells
Inner: intestines
Stem cells are unique body cells. They
can come from adults and embryo’s
• Stem cells have the ability to
–
–
–
–
Divide and renew themselves
Remain undifferentiated in form
Develop into a variety of specialized cell types
When stem cells divide they form 2 stem cells or 1 stem
cell and 1 specialized cell
Stem Cell Classification
• Stem cells are classified into three types.
• When stem cells divide they form 2 stem cells or 1
stem cell and 1 specialized cell
– Totipotent, or growing into any other cell type
– Pluripotent, or growing into any cell type but a totipotent cell
– Multipotent, or growing into cells of a closely related cell
family
Adult stem cells (Somatic stem cell)
• Come from, brain,
liver, muscle,
dental and even
fat cells.
• Can even come
from children and
umbilical cord
blood.
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming
an inner cell mass. These cells are then removed and grown with nutrients.
Scientists try to control how the cells specialize by adding or removing certain
molecules.
Advantages and Disadvantages of Adult
stem cells
Advantages
• Grown in lab.
• Can be put directly
into the body with
very little chance of
rejection
• Less ethical issues
• May be pluripotent
rather than
multipotent
Disadvantages
• Few in number,
difficult to isolate and
tricky to grow in the
lab
• May contain more
DNA abnormalities
Embryonic stem cells
– Come from donated
embryo’s grown in a clinic
– Result of In-vitro fertilization
– Taken from undifferentiated
cells 3 – 5 days old
• Called Inner cell mass
• Don’t have any specific
cell characteristics
– Embryonic stem cells
are pluripotent and
can be grown indefinitely
in culture.
• Can become any of the
200 types of cells
Advantages and Disadvantages of
Embryonic stem cells
Advantages
Disadvantages
• Pluripotent
• Can be grown
indefinitely in culture.
• Can become any of
the 200 types of cells
• Body may reject the
cells
• Could grow
unchecked and
become a tumor
• Kills the embryo
– Creates ethical
issues
Currently realized and potential
benefits of Stem Cells.
• Used to treat leukemia
and lymphoma
• May cure disease –
diabetes
• Replace damaged organs
- heart
• May revolutionize the
drug development
process.
– Downside – time and
money
– Little chance to reach
patient
Stem Cell Wrap up
Do you think stem cell research
should be legal or illegal.
Answer the question at the
bottom of your notes!