Name parts "E" and “F.”
(Note: This filament is simplified in this diagram. In real life it is
much thicker with many more “E” structures.)
E= myosin head F= myosin filament
Structure “D” is named after its chain of protein “beads” called actin.
What is “A” in the diagram (light area on bead structure)?
What happens at "A" during a muscle contraction?
A= active site (on actin) The active site is like a “sticky
spot” on actin that the myosin head attaches to during a
Name parts "B" through “D.”
B= troponin C= tropomyosin D= actin filament (The actin
filament contains actin, troponin, and tropomyosin.)
The proteins “B” and “C” have control over whether the myosin heads
are attached to actin or not. Name “C” and tell its role in this job.
Tropomyosin (“C”) helps control when myosin can attach to actin
in muscle because it covers the active sites on the actin
Calcium that is released from the sarcoplasmic reticulum attaches to
protein “B” to begin a muscle contraction. What does this calcium
cause to happen that allows the muscle contraction to start?
The calcium released from the sarcoplasmic reticulum (SR)
sticks/binds to troponin (“B”). Troponin is like a limp “hand”
holding onto tropomyosin. When calcium binds to troponin, it
pulls tropomyosin off of the active sites. Once the active sites
are uncovered, the myosin heads can now attach to the active
sites on actin to begin a muscle contraction.