Which of the following ions binds to the troponin complex, initiating the contraction of a muscle?
A. Sodium
B. Potassium
C. Calcium
D. Phosphorus
When a muscle cell is stimulated by a nerve impulse, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm. The calcium ions bind to the troponin complex, which is a protein that regulates the interaction between actin and myosin filaments. The binding of calcium to troponin causes a conformational change that exposes the binding sites for myosin on the actin filaments. This allows the myosin heads to attach to the actin and pull the filaments past each other, resulting in muscle contraction.
Therefore, the Correct Answer is C.
More Questions on TEAS 7 Science
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Q #1: Which of the following correctly orders structures from simple to complex?
A. Cells, tissues, atoms, organs
B. Atoms, organs, tissues, cells
C. Atoms, cells, tissues, organs
D. Organs, tissues, cells, atoms
Answer Explanation
The correct answer is c. Atoms, cells, tissues, organs. This is the correct order of structures from simple to complex. Atoms are the smallest and simplest units of mater. Cells are made up of atoms and are the basic units of life.
Tissues are groups of similar cells that work together to perform a specific function. Organs are made up of different types of tissues and perform more complex functions.
A. Cells, tissues, atoms, organs is not the correct order from simple to complex.
B. Atoms, organs, tissues, cells is not the correct order from simple to complex.
D. Organs, tissues, cells, atoms is not the correct order from simple to complex.
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Q #2: To accurately measure the density of a series of small irregular solids made of plastic, wood, fibreglass, and glass, a student will need which of the following laboratory tools?
A. Graduated cylinder, water, weighing balance
B. Graduated cylinder, spectrophotometer, water
C. Graduated beaker, metric ruler, water
D. Weighing balance, Bunsen burner, metric ruler
Answer Explanation
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, a student will need a graduated cylinder, water, and a weighing balance. The student can use the water displacement method to determine the volume of each solid by measuring the volume of water displaced when the solid is submerged in a graduated cylinder filled with water. The mass of each solid can be measured using a weighing balance. The density can then be calculated by dividing the mass by the volume.
The other options are not correct because they do not provide the necessary tools to accurately measure the density of the solids. A spectrophotometer is used to measure light absorption and is not necessary for measuring density. A graduated beaker is less accurate than a graduated cylinder for measuring volume. A Bunsen burner is used for heating and is not necessary for measuring density.
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Q #3: Use the table below to answer the question. Object Mass (g) Time of fall (sec) 1 5.0 2.0 2 5.0 1.0 3 30.0 0.5 4 35.0 1.5 Which of the following conclusions is supported by the data?
A. Objects A and B will fall at the same rate.
B. The greater the mass of an object, the faster it will fall.
C. The time of fall is independent of the mass of the object.
D. Air resistance could be greater for A than for B.
Answer Explanation
