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 is correct regarding the pH scale?
A. A substance with a pH of 3 is two times more alkaline than a substance with a pH of 4.
B. A substance with a pH of 3 is 10 times more alkaline than a substance with a pH of 4.
C. A substance with a pH of 3 is two times more acidic than a substance with a pH of 4.
D. A substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4.
Answer Explanation
The correct answer is d. A substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4. The pH scale is a logarithmic scale, which means that each change of one pH unit represents a tenfold change in the hydrogen-ion concentration. A substance with a pH of 3 has a hydrogen-ion concentration that is 10 times greater than that of a substance with a pH of 4.
A. A substance with a pH of 3 is not two times more alkaline than a substance with a pH of 4.
B. A substance with a pH of 3 is not 10 times more alkaline than a substance with a pH of 4.
C. A substance with a pH of 3 is not two times more acidic than a substance with a pH of 4.
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Q #2: Which of the following structures is an exocrine gland?
A. Pineal gland
B. Parathyroid gland
C. Parotid gland
D. Pituitary gland
Answer Explanation
The parotid gland is an exocrine gland that secretes saliva into the mouth. Exocrine glands secrete their products into ducts that carry the secretions to the body's surface or into body cavities. The other options are endocrine glands, which secrete hormones directly into the bloodstream. The pineal gland secretes melatonin, the parathyroid glands secrete parathyroid hormone, and the pituitary gland secretes several hormones that regulate various bodily functions.
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Q #3: A researcher wants to gather data on the average wing strength of all birds found in the American Northwest. The researcher only has one small net, so all large birds were excluded from the study. The researcher's results were different than expected, but he believes his data include enough birds to estimate the strength of all birds. For which of the following reasons should this data be rejected?
A. Data contradict the control group
B. Data were different than expected
C. Data are biased by the methodology
D. Data cannot be displayed graphically
Answer Explanation
The correct answer is c. Data are biased by the methodology. The researcher's data should be rejected because they are biased by the methodology used to gather them. By only using a small net, the researcher excluded all large birds from the study. This means that the data do not accurately represent the average wing strength of all birds found in the American Northwest.
A. The data contradicting the control group is not a reason to reject the data in this case.
B. The data being different than expected is not a reason to reject the data in this case.
D. The data not being able to be displayed graphically is not a reason to reject the data in this case.
