Cytosolic Ca 2+ causes muscle contraction by______ a. Binding to troponin b. Bin
ID: 68027 • Letter: C
Question
Cytosolic Ca2+ causes muscle contraction by______
a. Binding to troponin
b. Binding to tropomyosin
c. Binding to myosin
d. Binding to actin
Muscle contraction is caused by_______
a. The shortening of actin filaments, caused by the ATP-dependent action of myosin
b. The shortening of myosin filaments, caused by the ATP-dependent action of actin
c. The sliding of myosin and actin filaments, caused by the ATP-dependent action of myosin
d. The sliding of myosin and actin filaments, caused by the ATP-dependent action of actin
When an action potential reaches a neuromuscular junction the result is____
a. Acetylcholine binds to receptors on the sarcoplasmic reticulum, causing Ca2+ to flood the cytosol
b. Acetylcholine binds to receptors on the sarcolemma (muscle plasma membrane), causing depolarization of the sarcolemma
c. Ca2+ binds to receptors on the sarcolemma, causing depolarization of the sarcolemma
d. Acetylcholine binds to troponin, allowing myosin to bind to actin
The step in the contraction cycle at which ATP binds to myosin is___
a. When myosin binds to actin
b. The “power stroke” when myosin slides the actin filament along
c. Just after the “power stroke”, in order to release myosin from actin
d. Immediately after Ca2+ enters the cytosol
Which of the following statements about the cytoskeleton is true?
a. The cytoskeleton is made up of four types of protein filaments.
b. The bacterial cytoskeleton is important for cell division and DNA segregation.
c. Protein monomers that are held together with covalent bonds form cytoskeletal filaments.
d. The cytoskeleton of a cell can change in response to the environment.
Explanation / Answer
1. a. Binding to troponin
The increased calcium in the cytoplasm tends to bind with troponin C to convert this to tropomyosin. Now the myosin binds to stationary actin filaments causing initiation if rigor mortis. The muscle remains in contracted state because of lack of ATP.
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