Biology Reference
In-Depth Information
Table 17.2 (continued)
Cell component
Function
However, the
conformon theory
of molecular machines
by conformational energy of proteins (i.e.,
conformons
)
confined within the inner membrane that can be produced
without the membrane acting as an osmotic barrier and the
transmembrane proton gradient is there to serve as the
communication channel between mitochondria and the rest
of the cell (Ji 1979, 1991).
9 Ribosome
Consists of approximately 60% RNA and 40% proteins. Acts as
molecular machine to synthesize polypeptides from amino
acids using mRNA as templates.
10 Endoplasmic
reticulum (ER)
A network of sacs that produce, process, and transport
molecules to be used inside and outside of the cell. It is
connected to the nuclear envelope and serves as a link
between the nucleus and the cytoplasm.
11 Golgi apparatus
To distribute and export the products of the cell to its external
environment. The Gogi apparatus modifies proteins and fats
produced in ER and prepares them for export to the outside
of the cell via secretory vesicles.
12 Proteosome
To control the intracellular level of proteins by regulated
degradation of unneeded or damaged proteins in
communication/coordination with protein-producing
ribosomes. The proteosome is a large protein complex found
in eukaryotes, archea, and some bacteria. It is a barrel-
shaped protein complex with internal channel and consists
of the core (20 S) and two adaptors (19 S) attached to the
ends of the core. The 19 S adaptors or caps recognize the
ubiquitinated target proteins for degradation and the 20 S
core carries out the task of protein degradation through its
proteinase activity localized in its interior.
13 Lysosome
To help digest foods and to degrade cellular waste products and
debris from the intracellular and extracellular spaces for
recycling. Lysosomes are spherical organelles containing
acid hydrolases (optimally active at pH 4.5) for digesting
endogenous or exogenous proteins and particles. The
lysosomal membrane protects the cytosol from undesired
attack of cellular components by lysosomal enzymes.
Lysosomes are also called “garbage disposal system” of
the cell that keeps the interior of the cell free of unneeded
materials (Ciechanover 2005).
14 Peroxisome
To oxidize fatty acids and other metabolites and to detoxify
hydrogen peroxides. Peroxisomes are a single membrane-
bound organelles that contain enzymes able to remove
peroxides and catalyze the
b
-oxidation of very long chain
fatty acids
15 Cilia
For unicellular eukaryotes to move around. In multicellular
organisms, cilia are used to move fluid or materials past an
immobile cell. Cilia protrude from the cell anchored on the
basal body and encased in the cell membrane. The filaments
within a cilium carries out forward and backward stroke
motions using free energy of ATP hydrolysis.
