Chapter 5 Cell Growth and Division Mr. Shilala DAHS 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. 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. vascular tissue leaf stem lateral roots primary root SYSTEMS root system shoot system CELL TISSUE ORGAN

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 have the ability to 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) 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. Come from, brain, liver, muscle, dental and even fat cells. Can even come from children and umbilical cord blood.

Advantages and Disadvantages of Adult stem cells 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 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 Body may reject the cells Could grow unchecked and become a tumor Kills the embryo Creates ethical issues Pluripotent Can be grown indefinitely in culture. Can become any of the 200 types of cells

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!