ch 3 life and death of a cell Flashcards
any given time an adult has between how many different cells
50-100 trillion
Cells come in about 260 different varities through they all originates from that
single cell in which you began your life
all cells have the same DNA
cells take on their specialized structure and function through the process called
differentiation
most often chemical triggers lead to differing
gene expressions
* that is some genes are turned on while others are turned off
this is how cardiac muscle cells and nervous cells can be dramatically different despite having the same DNA
cell differentiation is often a process with numerous intermediaries between the
stem cell and the final specialized one
a stem cell is an
undifferentiated cell that can give rise to cells that will then specialize
(or make more of themselves)
only very early in embryotic development do you find
totipotent stem cells
* those that can develop into any cell type found in our bodies including that of the placenta
as the embryo begins to organize the stem cells are now
pluripotent
* which means they can develop into any cell type except the placenta
once the embryo starts to form its layers
(endoderm, mesoderm, ectoderm)
the stem cells are now considered
multipotent
multipotent cells then follow one of three pathways
cells in the mesoderm can develop into muscles and bones (among other things) but cannot become skin; cells in the ectoderm are on that path
differentiated cells then go on about their lives carrying out their
designated function until they either divide or die
some cells like skeletal muscle or neurons share your life span so technically they do neither)
some cells such as bone cells for ex
do not undergo
mitosis
new cells come from
stem cells
once a cell reaches its genetically determined expiration date it begins the process of
programmed cell death (apoptosis)
this continous step-wise process ultimately leads to the cell
shattering
