Nucleus
 A
NUCLEUS
acts as the control center for the cell. It contains DNA that directs
all functions of the cell. The nucleus has its own lipid bilayer
membrane with large pores. Thus the nuclear membrane is also a selectively
permeable membrane that regulates what can enter or leave the nucleus.
The nucleus has a similar function to the brain of the body.
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NUCLEOLUS
A nucleus usually contains several larger dark-staining bodies of DNA,
RNA, and protein called nucleoli (means little nucleus). One of these bodies
is called a NUCLEOLUS.
Nucleoli contain the genes and proteins that control the synthesis of RNA
for the ribosomes.
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CYTOPLASM
CYTOPLASM
is
actually salt water with additional nutrients, salts (ions), and waste
products. Organelles are suspended in the cytoplasm and the cell
membrane separates the cytoplasm from the outside of the cell. The
cytoplasm is gel-like (like Jello.)
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ENDOPLASMIC
RETICULUM
ENDOPLASMIC RETICULUM is
a network of connected membrane tubes. Reticulum means little net
and endoplasmic means inside the cytoplasm. The endoplasmic reticulum
(E.R.) has three major jobs. It is where certain molecules are synthesized,
stored, and transported. Some endoplasmic reticulum (called smooth,
no ribosomes) is where fatty acids, steroids, and lipids are made.
Some E.R., called rough (with ribosomes), is where proteins are made.
After proteins are made in the endoplasmic reticulum they are packaged
into little transport bodies called VESICLES.
These shuttle across the cytoplasm to the GOLGI APPARATUS.
Thus the rough E.R. and the Golgi apparatus and vesicles are part of the
cell's highway system because they are involved in moving proteins around
the cell and to the outside of the cell. This cell's highway system
is called PROTEIN TRAFFICKING.
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GOLGI APPARATUS
The GOLGI APPARATUS
is a bunch of hollow membranous sacs stacked on top of each other like
a series of hot water bottles. They are connected so that they share
a single inside compartment. Protein arrives at the Golgi in transport
vesicles from the endoplasmic reticulum and leaves the Golgi packaged in
membrane-bound vesicles to go to other organelles or to the outside of
the cell.
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