Prokaryotes
have several structures sticking out from them; hairlike pili.(function
largely unknown).and
bacterial
flagellum.(bacteria
that swim which have propellor like movements).used
for locomotion.
This motor turns the long, helical.flagellum.propelling
the cell
through its environment.
Eukaryotic cells contain
a number of subcellular
spaces that are separated from the cytoplasm
by their own membranes.
These are called organelles,
which allow this cell to conduct specialized functions in specialized compartments.
One specialized organelle is the nucleus
containing the cell's DNA.
Many other fascinating parts
for cellular functions occur. The 'simpler' prokaryotes include; nuclear
pores, mitochondria,
lysosomes,
endoplasmic
reticulum, with its smooth and rough sides, Golgi
apparatus, cytoskeltons
with its microtubules.(made
of actin, a specific
protein).and
its protein filaments.comprising
three different thicknesses, like three gauges.(sizes).of
wire; macro filaments and intermediate sized filaments, mitotic
spindles, chromosomes.(and
in the case of plants, added to these prokaryotes is cholorplast
containing chlorophyll), vacules,
covalent
hoarding of atoms to form molecules
with their compositional materials, amino
acids, proteins.(which
typically contain 50 to 3,000 amino acids),
nucleic
acids with its parts, either ribose.(RNA).which
has a composition attached made from specified
combinations of its 4 bases, being adenine,
cytidine,
uracil
and
guanine,
or deoxyribose.(DNA),
which similarly has adenine, cytidine, guanine and
thymine.
Uracil replaces thymine.
This design allows for the code's meaning to remain consistent for both
RNA and DNA, while affecting the chemical mechanisms. It's like typing
a word with one letter in a different font, CAR as compared to car. The
information is clear, the meaning remains the same; yet the composition
varies, there being more chemicals.(ink,
if this was paper).in
this composition.(CAR).than
in this one.(car
or Car).
An amino
acid side chain gives an amino acid its particular character.
It is the particular shape of a
folded protein and the precise position of the different kinds of amino
acids that allow a protein to function in the various ways it does.
Complexity is evidenced in
the 'enzyme sacks' called bacterial
cells.(prokaryotes).
Here there are many levels of subcellular organization, for example; a
typical Escherichia coli cell is surrounded by two membranes enclosing
a periplasmic compartment that is used for acquiring and sorting nutrients
and wastes. The center of the cell contains DNA strands folded into a compact
nucleoid,
forming a loosely defined compartment devoted to storage and use of genetic
information. The cytoplasm occupies the remaining portions of the cell
and is filled with ribosomes
and many different enzymes.
Many proteins are formed into complexes and thus enabled, subsequently
engage in many tasks. Some of these complexes combine several tasks to
increase efficiency. For example, molecules are delivered step to step
by the use of a flexible arm.
Proteins
are created and folded and old ones are dispensed with, thanks to the functioning
chaperonins and proteasomes.
This
is.extremely
complex and requires highly efficient coding.
There is astonishing complexity
involved in how DNA polymerase.(a
polynucleotide).is
the repository
and copying factory of genetic
information, telling the cell how to make polypeptides.
How does a cell know when
to transcribe
a gene?
How does it select a specific gene from the thousands available? How does
the information get transferred from one 'polymer'
language to the other?
A cell makes an RNA
copy of a small portion of its DNA.(called
a gene).by
a process called
transcription
which codes for a protein.(a
special protein is manufactured using the DNA code).and
by a process termed as translation,
whereby the information in the RNA is used to produce a protein by latching
onto DNA at a binding site that it selects for utilization of a particular
sequence.
The transcription of a gene
entails numerous decisions, one being where along the DNA chain to start.
This complicated, fascinating and mysterious
process involves balance of functioning, as when transcription is in
process.(forming),
it becomes overwound, yet automatically corrects by cutting strands of
overwound DNA, passing the uncut strands through the cut strands and then
resealing the cut. Transcription stops when the RNA runs into a special
DNA sequence.
In DNA replication, a great
deal of effort is required in cell division to ensure the genetic information
be copied and handed down uncorrupted. Tasks are necessary to ensure accuracy
in the copying of the two parent strands and their separation and unknotting
as they form. Enzymes
repair DNA damaged
by ultraviolet
light, chemical
mutagens,
or other environmental insults. The enzyme complex polymerase
unbinds the nucleotide double helix of the DNA.
