The Diversity of Cellular Life Chapter 7-4

Introducing….stem cells! This slide is designed to be interactive. Start with a question like “What do you think of when someone mentions stem cells?” and allow the students to suggest key words. At the click of a mouse in will come key words associated with stem cell research. 2

Introducing stem cells 3

I. What are stem cells? the body is made up of about 200 different kinds of specialized cells such as muscle cells, nerve cells, fat cells and skin cells all cells in the body come from stem cells a stem cell is a cell that is not yet specialized the process of specialization is called differentiation once the differentiation pathway of a stem cell has been decided, it can no longer become another type of cell on its own This slide introduces some basic terms and concepts about stem cells. 4

Embryonic stem cells (pluripotent) Tissue stem cells (multipotent) II. What makes stem cells so special? Stem cells can: self-renew to make more stem cells differentiate into a specialized cell type Embryonic stem cells (pluripotent) Stem cells that can become many types of cells in the body are called pluripotent Tissue stem cells (multipotent) Stem cells that can become only a few types of cells are called multipotent This slide explains the basic properties of stem cells and introduces the concept of classification based on potency.

III. Sources of Stem Cells A. Human embryos (Pluripotent) 1. Very controversial 2. Raises many moral and ethical questions B. Also found in human tissues (multipotent): 1. Adult bone marrow 2. Umbilical cord blood cells.

IV. Somatic Cell Nuclear Transfer A. Recently scientists have been able to reverse the “clock” of cells from adult tissue and turn them into embryonic like cells! B. One day we may be able to replace damaged tissue with stem cells from our own body!

VI. How do cells become Specialized? It starts with fertilization of an egg cell by a sperm cell which creates a zygotye (The organisms first somatic cell). The zygote will: Make IDENTICAL copies of itself by mitosis Become a ball of TOTIPOTENT cells (stem cells that could separate from each other and produce a new organism. Identical twins, triplets, etc. As more cells are produced by mitosis, they will form a BLASTOCYST, made of PLURIPOTENT stem cells.

VII. Pluripotent(stem)cells All have exactly the same DNA. Have the POTENTIAL to become ANY TYPE OF CELL in the organism!! Can NOT become a brand new fetus, like Totipotent cells can. Once pluripotent cells differentiate or specialize into a specific type of cell in the organism, they can not become any other cell. Can come from a blastocyst in an early developing fetus or umbilical cord blood or bone marrow cells after birth!

VIII. Pluripotent cells have the potential to treat disorders/conditions such as: Spinal cord injuries Parkinson’s Diabetes Amputations Hemophilia Serious skin injuries

IX. Cell Specialization =DIFFERENTIATION A. Once a pluripotent cell turns into a specific type of cell in the organism, it has differentiated or specialized and cannot change.

B. Cells in multi-cellular organisms become SPECIALIZED by turning ON the genes needed for a particular cell’s function and turning OFF the genes not necessary for that cell to function. Nerve cell Skin cell Muscle cell Stem or Pluripotent cell

a. Protein called hemoglobin carries the oxygen in the RBC. 1. Red blood cells transport O2, and CO2 a. Protein called hemoglobin carries the oxygen in the RBC. b. So, RBC’s need genetic info for making hemoglobin turned on.

A Day in the Life of a Red Blood Cell

So, genes for making proteins like insulin need to be turned on. 2. Cells in the pancreas produce proteins that function as hormones and enzymes important in the breakdown of food. So, genes for making proteins like insulin need to be turned on. Photo Credit: ©Don Fawcett/Photo Researchers, Inc.

3. Striated muscle cells allow movement So, Genes necessary for proteins that allow muscles to contract must be turned on. Photo Credit: ©Manford Kage/Peter Arnold, Inc.

SPECIALIZED ANIMAL CELLS Muscle cells Red blood cells Cheek cells

B. Specialized Plant Cells Plants exchange carbon dioxide, oxygen, water vapor, and other gases through tiny openings called stomata on the undersides of leaves. Highly specialized cells, known as guard cells, regulate this exchange.

Specialized Plant cells Guard cells Xylem cells Pollen