1/5/2015

• Happy New Year!• Presentations of your organelle analogies.• Differentiation of cells• Stem Cell Video Project• HW: Organelle Shape reading: • Summary of each section with key points.

• As cells divide they specialize.

• All of your cells have the same DNA but what is “on” changes

• Chemical signals turn DNA on or off

Differentiation: You were a single cell.

• You are ~7.5 TRILLION cells.

• ~200 different types – work together – form the tissues that

make up organs.• To do their “jobs”– cells come in

different sizes & shapes

– have different numbers of each organelle.

Example of Specialization

Macrophage (White Blood Cell)

• Specialized to digest invading bacteria

Red Blood Cell

• Specialized to carry oxygen (no nucleus or mitochondria)

• about 50 divisions from fertilized egg to “adult”– Adult cell is done dividing…not only in adults in babies too.

• Once the cells reach “adulthood” they are done differentiating.

• Some cells retain the ability to divide and differentiate. They are called “adult (or tissue) stem cells”.

• A stem cell is a cell that is not completely differentiated or “programmed”.

Where are stem cells found?

embryonic stem cellsblastocyst - a very early

embryo

tissue stem cellsfetus, baby and throughout life

Embryonic

• Unprogrammed, can develop into anything• Use in science is controversial

Adult (tissue): semi-programmed

Tissue stem cells:Where we find them

muscles

skin

surface of the eye brain

breast

intestines (gut)

bone marrow

testicles

Induced pluripotent stem cells (iPS cells)

cell from the body

‘genetic reprogramming’= add certain genes to the cell

induced pluripotent stem (iPS) cellbehaves like an embryonic stem cell

Advantage: no need for embryos! all possible types ofspecialized cells

culture iPS cells in the lab

differentiation

Induced pluripotent stem cells (iPS cells)

cell from the body (skin)

genetic reprogramming

pluripotent stem cell(iPS)

differentiation

neuronsgrow under conditions B

Stem cells: Challenges

embryonic stem cells

skin

grow under conditions A

blood

grow under conditions C

liver

grow under conditions D

?

Stem Cell Project and HW

• HW: read the on-line cell shape article• Project: rest of class today finish the majority

or research & planning. Next class bring any props. Time to finalize, record/send to me.