The blood transports more CO2 in the form of _____ than in any other form.
Carbaminohemoglobin
Carboxyhemoglobin
bicarbonate ions
dissolved CO2 gas
bisphosphocarbonate
The Correct Answer is C
A. Carbaminohemoglobin: Approximately 23% of carbon dioxide is transported by binding to the globin amino groups of the hemoglobin molecule. While this is a significant transport mechanism, it is secondary to the ionic pathway in the plasma. It primarily occurs after oxygen is unloaded at the systemic tissues.
B. Carboxyhemoglobin: This term describes the stable complex formed when carbon monoxide, not carbon dioxide, binds to the heme iron of hemoglobin. This condition is pathological and interferes with oxygen transport. It is not a normal physiological mechanism for the excretion of metabolic carbon dioxide.
C. bicarbonate ions: About 70% of metabolic carbon dioxide is converted into bicarbonate ions within erythrocytes by the enzyme carbonic anhydrase. These ions then diffuse into the plasma for transport to the lungs. This represents the most voluminous and efficient method for carrying carbon dioxide in blood.
D. dissolved CO2 gas: Only about 7% to 10% of carbon dioxide is transported physically dissolved in the blood plasma. Due to the limited solubility of gases in aqueous solutions, this method cannot accommodate the high metabolic output of tissues. Most of the gas must be chemically converted to be carried.
E. bisphosphocarbonate: This molecule is not a recognized physiological transporter of carbon dioxide in human hematology. It may be confused with 2,3-bisphosphoglycerate, which regulates hemoglobin's oxygen affinity. It plays no role in the chemical buffering or transport of carbon dioxide within the circulatory system.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. carbohydrates, proteins, and minerals: While minerals are essential micronutrients, they are required in much smaller quantities compared to the primary macronutrients. They do not constitute a major class of energy-yielding organic compounds. The physiological bulk of the diet consists of carbon-based macromolecules rather than inorganic elements.
B. fats, proteins, and carbohydrates: These three categories represent the fundamental macronutrients required for human energy production and structural maintenance. Carbohydrates provide immediate glucose, proteins supply amino acids for tissue repair, and fats offer concentrated energy storage. They comprise the largest mass of ingested nutritional matter.
C. proteins, nucleic acids, and carbohydrates: Nucleic acids are present in all cellular food sources but are not considered a primary nutritional class for energy. The body synthesizes most required nucleotides endogenously rather than relying on high-volume dietary intake. They do not provide significant caloric value compared to fats.
D. triglycerides, starches, and proteins: Triglycerides and starches are specific subcategories of lipids and carbohydrates, respectively. This choice is too narrow because it excludes other important forms such as phospholipids or simple sugars. A comprehensive classification requires the broader categorical terms for fats and carbohydrates.
E. proteins, fats, and minerals: This selection incorrectly elevates minerals to the status of a primary abundant class alongside macronutrients. Micronutrients like minerals are necessary for enzymatic function but are consumed in milligram or microgram amounts. Fats and proteins are consumed in much larger gram quantities daily.
Correct Answer is ["Erythropoietin"]
Explanation
In response to inadequate oxygen transport, the kidneys and liver increase the synthesis and secretion of the glycoprotein hormone erythropoietin (EPO). This hormone is released into the systemic circulation to act as a chemical messenger. It serves as the primary stimulus for the acceleration of red blood cell production.
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