Cell Specialization
All organisms are composed of cells. Unicellular organisms are
composed of a single cell. Multicellular organisms are composed
of many specialized cells. Specialized cells differ in structure
(size, shape...) and function (the role they perform in the
organism). The structural modifications that occur in a
specialized cell equip it to do its job in the organism. An adult
human is composed of approximately 100 trillion cells and has
over 200 different types of specialized cells.
Examples of Specialized Cells
Sperm Cell
http://utahhealthsciences.net/customer/image_gallery/373/13SEM.J
PG
Fat Cells
www.broadinstitute.org
,White Blood
Cell
http://medpediamedia.com/u/653px-
SEM_Lymphocyte.jpg/653px-SEM_Lymphocyte_large.jpg
Macrophage
s
surrounding www.eyeofscience.com
parasite
The life cycle of a cell consists of a growth phase (interphase)
followed by a division phase (either mitosis or meiosis).
Some cells cycle between interphase and division continuously
through the life of an organism. This allows the body to
produce new cells allowing for growth and maintenance of
tissues. Other cells exit the cell cycle and enter a non-dividing
phase called GO. Depending on environmental signals, they may
reenter the cell cycle or remain in GO permanently.
A cell specializes while in interphase or GO. The process in
which a cell becomes specialized is called differentiation and
occurs when the cell selectively activates or inactivates specific
genes.
The specialized cells of an organism contain the exact same
complement of genes. In humans, this means that each cell type
contains approximately 30,000 genes. This is because each cell
is the descendent of a single cell (the fertilized egg) that
underwent mitotic cell division to form a multicellular organism
, during embryonic development. Cell differences are the result
of differences in gene expression. A gene is expressed
(activated) when it is transcribed and translated into a protein.
scienceblog.com
Some genes (such as those responsible for glucose metabolism
or protein synthesis) are expressed in all cells. Other genes
are expressed in a single or select few specialized cells. The
expression of a gene within a particular specialized cell changes
over an individual’s life. For example, all human cells contain a
gene that codes for caesin, the major protein found in
milk. However, the gene is only expressed milk producing cells
of lactating females.
All organisms are composed of cells. Unicellular organisms are
composed of a single cell. Multicellular organisms are composed
of many specialized cells. Specialized cells differ in structure
(size, shape...) and function (the role they perform in the
organism). The structural modifications that occur in a
specialized cell equip it to do its job in the organism. An adult
human is composed of approximately 100 trillion cells and has
over 200 different types of specialized cells.
Examples of Specialized Cells
Sperm Cell
http://utahhealthsciences.net/customer/image_gallery/373/13SEM.J
PG
Fat Cells
www.broadinstitute.org
,White Blood
Cell
http://medpediamedia.com/u/653px-
SEM_Lymphocyte.jpg/653px-SEM_Lymphocyte_large.jpg
Macrophage
s
surrounding www.eyeofscience.com
parasite
The life cycle of a cell consists of a growth phase (interphase)
followed by a division phase (either mitosis or meiosis).
Some cells cycle between interphase and division continuously
through the life of an organism. This allows the body to
produce new cells allowing for growth and maintenance of
tissues. Other cells exit the cell cycle and enter a non-dividing
phase called GO. Depending on environmental signals, they may
reenter the cell cycle or remain in GO permanently.
A cell specializes while in interphase or GO. The process in
which a cell becomes specialized is called differentiation and
occurs when the cell selectively activates or inactivates specific
genes.
The specialized cells of an organism contain the exact same
complement of genes. In humans, this means that each cell type
contains approximately 30,000 genes. This is because each cell
is the descendent of a single cell (the fertilized egg) that
underwent mitotic cell division to form a multicellular organism
, during embryonic development. Cell differences are the result
of differences in gene expression. A gene is expressed
(activated) when it is transcribed and translated into a protein.
scienceblog.com
Some genes (such as those responsible for glucose metabolism
or protein synthesis) are expressed in all cells. Other genes
are expressed in a single or select few specialized cells. The
expression of a gene within a particular specialized cell changes
over an individual’s life. For example, all human cells contain a
gene that codes for caesin, the major protein found in
milk. However, the gene is only expressed milk producing cells
of lactating females.
