Which of the following ions binds to the troponin complex, initiating muscle contraction?
Potassium.
Calcium.
Phosphorus.
Sodium.
The Correct Answer is B
Calcium ions play a crucial role in initiating muscle contraction.
When a muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm.
Some of this calcium attaches to troponin, which causes it to change shape. This shape change exposes binding sites for myosin on the actin filaments.
Myosin’s binding to actin causes cross-bridge formation, and muscle contraction begins.
The other ions mentioned in the question do not have this specific role in muscle contraction.
Potassium ions are important for maintaining the resting membrane potential of cells, but they do not bind to the troponin complex.
Phosphorus ions are important for energy metabolism but do not bind to the troponin complex.
Sodium ions are important for generating action potentials but do not bind to the troponin complex.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Cytokines are chemicals released by one type of immune cell to directly activate another type of immune cell.
They are small proteins that act as messengers between cells and play a key role in regulating the immune response.
Choice B. Lysozymes is not the correct answer because lysozymes are enzymes that break down bacterial cell walls and do not directly activate other immune cells.
Choice C. Perforin is not the correct answer because perforin is a protein that forms pores in the membranes of target cells and does not directly activate other immune cells.
Choice D. Granzymes is not the correct answer because granzymes are enzymes that enter target cells and trigger apoptosis (cell death) and do not directly activate other immune cells.
Correct Answer is B
Explanation
Electrophoresis is a technique that uses an electric field to separate charged molecules, such as DNA fragments, based on their size and charge.
Choice A is not correct because titration is a laboratory method used to determine the concentration of a solution.
Choice C is not correct because filtration is a laboratory method used to separate solids from liquids.
Choice D is not correct because spectrophotometry is a laboratory method used to measure the absorbance of light by a solution.
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