Cell Biology 2B Intro to Cells Continued, Ultrastructure of Cells.notebook
Introduction to Cells Continued and Ultrastructure of Cells

January 30, 2015

Gene Expression and Cell Differentiation
All Cells have the same set of genes- the genes that are used determine differentiation
Example
- rod cells (pigment to absorb light)
- lens (no pigment)
Genes for pigmentation only used in rod cells
Extra "instruction manual" for all cells
25,000 genes in human genome, but most cells less than half will be used

itshumour.blogspot.com

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When a gene is being used, it is being "expressed" can make proteins* Cell differentiation occurs because a unique sequence of genes is expressed for each cell type

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Cell differentiation in olfactory receptors
Each cell expresses only one
"smell"
gene-- why we can detect so many kinds of smells

Stem Cells
Life begins when a sperm fertilizes an egg

zygote

Cell division occurs- 2, 4, 8, 16...

In these early stages of cell division and embryonic development, large amounts of undifferentiated tissue is formed- all other tissues stem from these

These cells begin to differentiate as the embryo develops. catalog.flatworldknowledge.com Jan 30-9:52 AM

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Cell Biology 2B Intro to Cells Continued, Ultrastructure of Cells.notebook

January 30, 2015

Significance of STEM cells
Stem cells can divide over and over to make large quantities of new cells- can help replace cells that have been lost or damaged
Can differentiate in several ways to produce many different cell types www.systembio.com Jan 30-9:42 AM

Therapeutic Uses

re-grow skin- burn victims replace lost/malfunctioning cells- Type I
Diabetes
potential to replace whole organs hearts, kidneys, etc.

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As cells develop, they eventually are forced to differentiate, and choose a certain pathway...BUT...
Some cells stay stem cells into adulthood, valuable for repair!
Ex) bone marrow, skin, liver, brain, kidney, heart

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Electron Microscopes
Have a much higher resolution than light microscopes
Resolution = making the separate parts of an object distinguishable by eye
Light microscopes, cells can be seen
> Max resolution = 200 nm (*400)
Electron microscopes, ultrastructure can