Which of the following ions binds to the troponin complex, initiating contraction of a muscle?

A. Sodium

B. Potassium

C. Calcium

D. Phosphorus

Answer Explanation:

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.

Q #1: Which of the following is the structure through which blood exits the glomerulus?

A. Proximal tubule

B. Distal tubule

C. Afferent arteriole

D. Efferent arteriole

Answer Explanation

The glomerulus is a network of capillaries that filters blood and forms the primary urine. The blood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. The efferent arteriole has a smaller diameter than the afferent arteriole, creating a high pressure in the glomerulus that facilitates filtration.
Q #2: Which of the following statements best describes the function of erythropoietin in the human body?

A. It aids in lowering oxygen levels in the blood.

B. It aids in raising levels of clotting factors in the blood.

C. It aids in raising hemoglobin levels in the blood.

D. It aids in lowering CO2 levels in the blood.

Answer Explanation

Erythropoietin is a hormone that is produced by the kidneys and stimulates the production of red blood cells in the bone marrow. Red blood cells contain hemoglobin, a protein that binds to oxygen and transports it to the tissues. Therefore, erythropoietin helps to maintain adequate oxygen levels in the blood and prevent anemia.
Q #3: Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host T-cell after the AIDS virus enters the cell?

A. Reverse transcriptase, an enzyme encoded by the virus.

B. Receptor proteins located on the surface of the virus.

C. The phospholipids found on the envelope of the virus.

D. The protein that makes up the capsid of the virus.

Answer Explanation

Reverse transcriptase, an enzyme encoded by the virus. This enzyme can convert the viral RNA into DNA, which can then integrate into the host cell's genome and hijack its machinery to produce more viruses. The other options are not relevant to this process. Receptor proteins are involved in binding the virus to the cell membrane, but they do not insert viral DNA into the cell. The phospholipids and the protein capsid are structural components of the virus, but they do not have any enzymatic activity.

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Which of the following ions binds to the troponin complex, initiating contraction of a muscle?

More Questions on TEAS 7 Science

Q #1: Which of the following is the structure through which blood exits the glomerulus?

Answer Explanation

Q #2: Which of the following statements best describes the function of erythropoietin in the human body?

Answer Explanation

Q #3: Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host T-cell after the AIDS virus enters the cell?

Answer Explanation

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