12.15.3 The Sliding Filament: Interaction of ATP, Actin, Myosin, and Calcium Flashcards
1
Q
The Sliding Filament: Interaction of ATP, Actin, Myosin, and Calcium
A
- The sliding filament theory is a model for muscular contraction.
- Myosin filaments interact with actin filaments using ATP to cause muscular contraction
2
Q
Review:
A
- The sarcoplasmic reticulum releases calcium ions
that bind to the troponin complex. The binding of calcium ions to troponin results in a change in the position of tropomyosin. The shift of the tropomyosin strand exposes the myosin binding sites of the actin filament so that muscular contraction can occur.
3
Q
note
A
- The diagram to the left depicts the model for muscular
contraction. - The myosin head bound to ATP is in its low-energy
configuration (shown in the upper left-hand corner of the diagram). - When ATP is hydrolyzed, the myosin head pulls back into its high-energy configuration.
- The myosin head then forms a cross-bridge with the actin filament. When ADP + Pi is released, the myosin head returns to its low-energy state and shifts the actin filament. The cycle continues when another molecule of ATP binds to the myosin head.
4
Q
The ATP used in muscle contractions comes from
A
- creatinine phosphate
5
Q
The strength of a contraction depends upon the
A
- number of units contracted.
- number of cross bridges that participate in the power stroke.
- availability of ATP.
6
Q
Sustained muscle contraction is caused by
A
- repeated interactions of the myosin and actin of the contracting units.
7
Q
The energy necessary for muscle contraction comes from
A
- ATP bound to the myosin heads
8
Q
The attachment of the myosin head to the actin filament causes
A
- the actin filament to slide to its contracted position as the myosin head returns to its original position.
9
Q
Simultaneous to Ca2+ binding to tropomyosin and exposing binding sites on actin,
A
- ATP is hydrolized into ADP + Pi causing the myosin head to move into a high energy position.
