Download Cillia and flagella

Cilia and flagella
Cilium , flagellum are projections of cells that can move both in an
undulating fashion like a whip or stiffly like an oar .cilia are short (2-10
µm ) while flagella are longer (usually no more than 200 µm).Ciliated
cells are critical to our respiratory health and to the ability to reproduce.
The ciliated cells that line our respiratory tract sweep debris trapped
within mucus back up the throat, which helps keep the lungs clean
similarly, ciliated cells move an egg along the oviduct, where it will be
fertilized by a flagellated sperm cell. A cilium and flagellum have the
same organization of microtubules within a plasma membrane covering
.Attached motor molecules ,powered by ATP ,allow the microtubules in
cilia and flagella to interact and bend ,and there by move .Cilia and
flagella grow from basal bodies ,structures that have the same
organization as centrioles ,which are structures located in centrosomes
outside the nucleus .
The importance of normal cilia and flagella is illustrated by the
occurrence of a genetic disorder .some individuals have an inherited
defect that leads to malformed microtubules in the cilia and flagella .Not
surprisingly ,they stiffer from recurrent and sever respiratory infections
,because the ciliated cells lining the respiratory passage fail to keep their
lungs clean ,they also are infertile due to the lack of ciliary action to
move the egg in a female or the lack of flagella action by sperm in male.
Other types of cell movements
We have already mentioned that the presence of actin filaments allows
microvilli (short projections of some cells) ,to increase or decrease in
save as assemble and dissemble .Actin filaments can also allow some
types of human cell to crawl .White blood cells can move out of the blood
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vessels into the tissues ,where they help defend us against disease –
causing agents .Then too actin filaments are necessary to the contraction
of muscle cells that allow all of us have the freedom of locomotion.
Mitochondria
Mitochondria (mitochondrion) are often called the powerhouse of the
cell – just as a powerhouse burns fuel to produce electricity; the
mitochondria convert the chemical energy of glucose product into the
chemical energy ATP molecule. In the process, mitochondria use up
oxygen and give of carbon dioxide and water. The oxygen you breathe in
enters cell and the mitochondria; the carbon dioxide you breathe out is
released by mitochondria. Because oxygen is involved, we say that
mitochondria carry on cellular respiration. Cellular respiration is a very
important of cellular metabolism.
Mitochondria are bounded by a double membrane. The inner
membrane is folded to form little shelve called cristae, which project into
the matrix, an inner space filled with a gel- like fluid. The matrix of a
mitochondrion
contains
enzymes
for
breaking
down
glucose
products.ATP production occurs at the cristae .The protein complexes
that aid in the conversion of energy are located in an assembly –line
fashion on these membranous shelves .
Every cell uses a certain amount of ATP energy to synthesized
molecules, but many cells use ATP to carry out their specialized
functions .For example, muscle cells use ATP for muscle contraction,
which produces movement, and nerve cells use it for the conduction of
nerve impulses, which make us aware of our environment.
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Cellular specialization
As advantage that multicellular aggregates and organism
have is that not every cell needs to perform every function. This
allows specialization. In sponges (kingdom animallia, phylum
porifera), cells are specialized but are not organized into tissues.
The cells of all other animal form tissues. A tissue consist of
similar cells and there product located together (structurally
integrated) and functioning together (functionally integrated).
The inner and outer cell layer of animals in the phylum cnidaria
are separate tissue with different function. Although , the cells in
the two layer are different , each cell is still changeable, so that
the cnidaria are able to regenerate an entire organism from a
small pieces .The
cellular flexibility of cnidaria (and other
organisms capable of regeneration from part ) contrasts with the
situation in more complex multicellular organisms in these
complex organisms ,the fate of the cell becomes more and more
restricted as it divides ,through a process called differentiation
.Initially ,a cell is capable of performing a variety of functions
but as the cell differentiation (literally ,becomes different ),its
progressively losses some of its abilities and becomes
specialized at doing only a few things very well .Some cells
such as human muscle or nerve cells ,loss so many important
abilities during differentiation that they may become incapable
of further cell division .
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In human cells, transcription activators are DNA – binding
proteins .Every cells contains many different types of
transcription activators and specific combination is believed to
regulate the activity of any particular gene. After the right
combination of transcription activators binds to DNA, RNA
polymerase attaches to DNA and begins the process of
transcription.
As cells mature, they differentiate and become specialized
.Specialization is determined by which genes are active, and
therefore by which transcription activators are present in that
cell .Signals received from inside and outside the cell could turn
on or of genes that code for certain transcription factors .For
example, the gene for fetal hemoglobin ordinarily gets turned
off as a new born matures, therefore one possible treatment for
sickle –cell disease is to turn this gene on again.
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