Which of the following ions binds to the troponin complex, initiating contraction of a muscle?
A. Potassium.
B. Calcium.
C. Phosphorus.
D. Sodium
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 crossbridge formation, and contraction of the muscle 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 they do not bind to the troponin complex.
Sodium ions are important for generating action potentials, but they do not bind to the troponin complex.
Therefore, the Correct Answer is B.
More Questions on TEAS 7 Science
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Q #1: Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host cell after the AIDS virus enters the cell?
A. The phospholipids found on the envelope of the virus.
B. Reverse transcriptase, an enzyme encoded by the virus.
C. Receptor proteins located on the surface of the virus.
D. The protein that makes up the capsid of the virus.
Answer Explanation
Reverse transcriptase, an enzyme encoded by the virus.
Reverse transcriptase is a virus-specific enzyme that transcribes an RNA template to DNA1.
This allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host cell after the AIDS virus enters the cell.
Choice A, The phospholipids found on the envelope of the virus, is not the correct answer because phospholipids are a major component of cell membranes and do not play a direct role in inserting viral DNA into the DNA of a host cell.
Choice C, Receptor proteins located on the surface of the virus, is not the correct answer because receptor proteins located on the surface of the virus play a role in attachment and fusion of HIV virons to host cells, but do not play a direct role in inserting viral DNA into the DNA of a host cell.
Choice D, The protein that makes up the capsid of the virus, is not the correct answer because capsid is the outer protein shell of a virus and does not play a direct role in inserting viral DNA into the DNA of a host cell.
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Q #2: Which of the following physiological responses is caused by the release of antidiuretic hormone?
A. Increase in the concentration of calcium in the glomerulus.
B. Increase in water reabsorption in the collecting duct
C. Decrease in the concentration of calcium in the glomerulus.
D. Decrease in water reabsorption in the collecting duct
Answer Explanation
Antidiuretic hormone (ADH), also known as vasopressin, is a hormone that helps regulate the amount of water in your body.
It works to control the amount of water your kidneys reabsorb as they filter out waste from your blood.
Choice A is not correct because an increase in the concentration of calcium in the glomerulus is not a physiological response caused by the release of antidiuretic hormone.
Choice C is not correct because a decrease in the concentration of calcium in the glomerulus is not a physiological response caused by the release of antidiuretic hormone.
Choice D is not correct because a decrease in water reabsorption in the collecting duct is not a physiological response caused by the release of antidiuretic hormone.
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Q #3: In a plant in which fuzzy leaves (F) are dominant over smooth leaves (f), which of the following crosses will produce only offspring with smooth leaves?
A. FF x FF
B. Ff x Ff
C. ff x ff
D. Ff x ff
Answer Explanation
ff.
In this cross, both parents are homozygous recessive for the smooth leaf trait
(ff).
This means that all of their offspring will inherit two copies of the recessive allele (f) and will therefore have smooth leaves.
Choice A.
FF x FF is not correct because both parents are homozygous dominant for the fuzzy leaf trait (FF) and all of their offspring will inherit two copies of the dominant allele (F) and will therefore have fuzzy leaves.
Choice B.
Ff x Ff is not correct because both parents are heterozygous for the leaf trait (Ff) and their offspring can inherit either one dominant allele (F) or one recessive allele (f) from each parent, resulting in a 3:1 ratio of fuzzy to smooth leaves. Choice D.
Ff x ff is not correct because one parent is heterozygous for the leaf trait (Ff) while the other is homozygous recessive (ff), resulting in a 1:1 ratio of fuzzy to smooth leaves in their offspring.
