Mrs. P Honors Biology. Unit 5: Cell structure and function. Cell Theory. In 1665, Englishman Robert Hooke used an early light microscope to look at a thin slice of cork. Under the microscope, cork seemed to be made of thousands of tiny, empty chambers.
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Each of the specialized cell types found in the adult develops from the same fertilized egg cell.
Cells throughout an organism develop in different ways to perform different tasks. This process is called cell specialization.
Different types of cells have different types of shapes and parts so that they can perform different functions.
A series of genes called the HOX genes control the differentiation of the cells and tissues in the embryo.
During the process of differentiation, only specific parts of the DNA are activated. Different parts of the genetic instructions are used in different types of cells (this is influenced by the cell’s environment)
Because all the cells in an organism contain the same DNA, they initially have the potential to become any type of cell; however, once a cell differentiates, the process cannot be reversed.
Red Blood cells – have a small disc like shape to increase the surface area for oxygen absorption; hemoglobin binds and carries oxygen; no nucleus to make more space for the hemoglobin
Muscle cells- A muscle cell is generally elongated and elastic containing mitochondria in large number. The elongated and elastic feature helps muscle tissues to contract; the mitochondria make more ATP for the cell.
Xylem – have a thick cell wall and hollowed center; used to transport water upward from the roots of a plant
Phloem – a specialized plant tissue used for transporting nutrients and glucose; made of specialized cells called sieve tube cells and companion cells.
Stomata – Where transpiration occurs in a plant. Guard cells surround the stoma and open and close to let water in or out.
Embryonic stem cells – found in an embryo; controversial because have to destroy the embryo; are pluripotent (can turn into almost any type of cell)
Adult stem cells – found mostly in bone marrow, but also in liver, brain, skin, and some muscle cells; not as useful as embryonic stem cells.
Umbilical cord/placenta – doctors can now collect an infant’s cord blood; can be used to cure some cancers, blood disorders, and immune disorders.