Glucose appears in the urine of an untreated diabetic because
Correct answer: A. the blood glucose level exceeds the capacity of the tubule carriers to reabsorb it
- A. the blood glucose level exceeds the capacity of the tubule carriers to reabsorb it
- B. glucose is too large to be reabsorbed
- C. the glomerulus stops filtering glucose
- D. insulin is secreted into the filtrate
Explanation
Reabsorption of glucose depends on a fixed number of carrier proteins in the proximal tubule, and once the blood concentration passes the renal threshold of roughly 180 mg per 100 cm3 the carriers are saturated and the surplus stays in the filtrate. The unabsorbed glucose then holds water osmotically, which explains the large urine volume and the constant thirst of an untreated diabetic.
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The kidney and urinary system remove nitrogenous wastes, regulate water and ion balance, and help maintain blood pH through filtration, selective reabsorption and secretion. Questions cover nephron structure, ultrafiltration, the loop of Henle, collecting ducts, urine formation and the roles of ADH and aldosterone, while distinguishing excretion from egestion.
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