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Actin is one of the protein molecules that (together
with myosin, tropomyosin,
and troponin) forms the cylindrical structures called myofibrils that,
together, form muscle
fibers.
Myofibrils consist of two types of protein filaments, called
thin
filaments, and thick
filaments. Actin molecules, together with
tropomyosin and actin molecules, form the thin filaments which have
a helix structure - as shown in the diagram below.
Above: Diagram of Actin molecules within a Thin Filament.
Actin molecules are the points of attachment (on the thin
filaments) for the myosin heads (which are part of the thick filaments).
Actin has an important combination of strength
and sensitivity. Actin filaments are and continually constructed
and disassembled
as needed and directed for the correct function of the tissue of which
actin is a part. This
dynamic character of actin is controlled by a molecule of Adenosine
Triphosphate (ATP)
bound
to each actin monomer. The state of the ATP
determines the stability of the actin
filament.
For further detail about actin, visit Rensselaer
Polytechnic Institute's website.
This Section consists of short summaries about the
structures that form the muscles of the body.
This list is not exhaustive but is intended to be appropriate for students
of A-Level Human Biology, ITEC courses in massage and related subjects,
and some other courses in Health Sciences. Visitors
are encouraged to supplement their study by reading many different sources.
For more general information about Muscles see
the pages about:
Anterior
Muscles, Posterior
Muscles, Facial
Muscles, Terminology
about Muscles, and the Structure
of Muscles. |
