Biology Questions and Answers
sarcomeres blocks of actin and myosin
molecules armanner. The sarcomee posed in organizedres align in
sequence forming myofibrils that are
longitudinallythe muscle fibers (cells). placed in the cytoplasm o The grouping f
of consecutive blocks of actin and
myosin striped pattern oin parallel filamef the striated mnts creates theuscle
tissue seen under the microscope.
- What are sarcomeres?
Sarcomethe muscle tissue formed of alternatingres are the contractile units of (^)
actin blocks (thin filaments) and myosin
blocks (thick filaments). Sevsarcomeres placed in linear sequenceeral (^)
form a myofibril. Therefore one muscle
fiber (cell) has masacomeres. ny myofibrils made of
The compartmeinserted are delimitents where myofibrils ared by an excitable
membrane known as sarcolemma. The
sarcolemma is ththe muscle cell. e plasma membrane of
- What are the main
proteins that constitute the
sarcomere? What is the
function of those molecules in
the muscle cells?
In the sarcomere actin and myosin blocks.there are organized Troponin and (^)
tropomyosin also appear associated to
actin.
The actin molecules when activated by
calcium ions liof the sarcomerberated in the proximitiese are pulled by myosin
molecules. This interaction between
actin anoriginating d myosin the phenomenon of muscleshortens the myofibrils
contraction.
- What are the positions of
actin and myosin molecules in
the sarcomere before and
during the muscle
contraction?
Schematicallyperpendicularly to b actin filaments attachedoth sarcomere
extremities (longitudinal sides) make
contact with myosin fpositioned in the middle of theilaments (^)
sarcomere and in parallel to the actin
filaments.
Before the contraction the are extended (relaxed) since thsarcomerese contact (^)
between actin and myosin filaments is
only madcontractione by their extremities. D actin filaments slide alouringng
the myosin filaments and the
sarcomeres shorten.
- How do calcium ions
participate in muscle
contraction? Why do both
muscle contraction and
muscle relaxation spend
energy?
In the muscle cellsstored within the sarcoplasmic calcium ions are
reticulum. Whstimulus for the muscle coen a motor neuron emitsntraction
neurotransmitters called acetylcholine
are released in the neuromuscularjunction and the sarcolemma is excited. (^)
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