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.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. adrenal medulla, epinephrine: The adrenal medulla secretes catecholamines like epinephrine in response to acute sympathetic stimulation. These hormones primarily influence cardiovascular and metabolic activity, such as increasing heart rate and glycogenolysis. They do not have a direct mineralocorticoid effect on renal sodium or water retention.
B. pancreas; cortisol: Cortisol is a glucocorticoid produced by the adrenal cortex, not the pancreas, in response to systemic stress. While it has minor mineralocorticoid activity at very high levels, its primary role involves metabolic regulation and immune suppression. The pancreas focuses on glucose homeostasis through insulin and glucagon.
C. kidneys; corticosterone: The kidneys secrete renin and erythropoietin but do not synthesize corticosterone. Corticosterone is a corticosteroid produced in the adrenal glands of many species. While the kidney is the target for mineralocorticoids, it does not produce them as a local or systemic secretion.
D. adrenal cortex aldosterone: The zona glomerulosa of the adrenal cortex secretes aldosterone, a potent mineralocorticoid. This hormone acts on the distal tubules of the kidney to stimulate the reabsorption of sodium ions, which leads to osmotic water retention. It is a critical component of the renin-angiotensin-aldosterone system.
E. thyroid; calcitonin: Calcitonin is secreted by the parafollicular cells of the thyroid gland to lower blood calcium levels. It inhibits osteoclast activity and promotes calcium excretion by the kidneys. It has no significant effect on the renal handling of sodium or the retention of total body water.
Correct Answer is True
Explanation
True: This clinical term describes the exudate formed during the inflammatory process, particularly in response to pyogenic bacterial infections. It consists of an accumulation of liquefied necrotic tissue, dead and dying leukocytes, and cellular debris. The presence of neutrophils is the hallmark of this acute inflammatory response.
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