Myoglobin __________.
Stores oxygen in muscle cells
Is a protein involved in the direct phosphorylation of ADP
Breaks down glycogen
Transports oxygen throughout the muscle tissue
Produces the end plate potential
The Correct Answer is A
Choice A reason: Myoglobin is a red pigment found in muscle cells that binds oxygen molecules. It serves as an oxygen reservoir, especially important during periods of intense muscular activity when oxygen demand exceeds supply. Its high affinity for oxygen allows it to release oxygen when intracellular levels drop, supporting aerobic metabolism.
Choice B reason: The protein involved in the direct phosphorylation of ADP is creatine kinase, which facilitates the transfer of a phosphate group from creatine phosphate to ADP. Myoglobin is not involved in this process.
Choice C reason: Glycogen breakdown is catalyzed by enzymes such as glycogen phosphorylase. Myoglobin does not participate in carbohydrate metabolism or glycogenolysis.
Choice D reason: Oxygen transport throughout the body is primarily the function of hemoglobin in red blood cells. Myoglobin stores oxygen locally within muscle cells rather than transporting it across tissues.
Choice E reason: The end plate potential is generated at the neuromuscular junction due to the influx of sodium ions following acetylcholine binding. This is an electrical event and does not involve myoglobin.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A reason: A foramen is a round or oval opening through a bone that allows the passage of nerves and blood vessels. It is a common anatomical feature found in various bones, such as the foramen magnum in the occipital bone or the infraorbital foramen in the maxilla.
Choice B reason: A fossa is a shallow depression in a bone, often serving as an articular surface or a site for muscle attachment. It does not serve as a passageway like a foramen.
Choice C reason: A meatus is a canal-like passageway through a bone, such as the external auditory meatus in the temporal bone. While it is a passage, it is more elongated and tunnel-like than a round or oval opening.
Choice D reason: A sinus is a cavity within a bone, typically filled with air and lined with mucous membrane, such as the paranasal sinuses. It is not an opening for passage but rather a hollow space.
Correct Answer is A
Explanation
Choice A reason: Parathyroid hormone (PTH) is secreted by the parathyroid glands in response to low blood calcium levels. It stimulates osteoclast activity, leading to bone resorption and the release of calcium into the bloodstream. PTH also enhances calcium reabsorption in the kidneys and activates vitamin D to increase intestinal calcium absorption.
Choice B reason: Thyroxine, produced by the thyroid gland, primarily regulates metabolism. While it influences bone growth and development indirectly, it does not directly stimulate osteoclast activity or calcium release.
Choice C reason: Osteocalcin is a non-collagenous protein secreted by osteoblasts and is involved in bone mineralization and calcium ion homeostasis. However, it does not stimulate osteoclast activity or increase blood calcium levels.
Choice D reason: Calcitonin is secreted by the parafollicular cells of the thyroid gland in response to high blood calcium levels. It inhibits osteoclast activity, thereby reducing bone resorption and lowering blood calcium levels. It acts in opposition to PTH.
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