Which of the following statements is incorrect w.r.t tubular reabsorp...
Tubular reabsorption in the kidney
Tubular reabsorption is an important process that occurs in the kidney to selectively reabsorb certain substances from the filtrate back into the bloodstream. It takes place in the renal tubules, which are part of the nephrons in the kidney. The reabsorption process ensures that essential substances, such as water, glucose, amino acids, and ions, are retained in the body while waste products are eliminated.
Incorrect statement: Substances like glucose, amino acids, and Na in the filtrate are always reabsorbed only passively, whereas nitrogenous wastes are absorbed by active transport.
This statement is incorrect because the reabsorption of glucose, amino acids, and sodium (Na+) in the renal tubules is primarily an active process. These substances are actively transported from the tubular lumen into the renal tubule cells and then across the basolateral membrane into the bloodstream.
Active reabsorption of glucose:
- Glucose is actively reabsorbed in the proximal convoluted tubule (PCT) of the nephron.
- It is transported from the tubular lumen into the tubule cells by sodium-glucose cotransporters (SGLTs).
- SGLTs use the energy derived from the sodium gradient created by the Na+/K+ ATPase pump on the basolateral membrane.
- Glucose is then transported across the basolateral membrane into the bloodstream by facilitated diffusion through glucose transporters (GLUTs).
Active reabsorption of amino acids:
- Amino acids are actively reabsorbed in the PCT along with sodium ions.
- They are transported from the tubular lumen into the tubule cells by sodium-amino acid cotransporters.
- These cotransporters use the energy from the sodium gradient created by the Na+/K+ ATPase pump on the basolateral membrane.
- Amino acids are then transported across the basolateral membrane into the bloodstream by facilitated diffusion.
Active reabsorption of sodium:
- Sodium reabsorption occurs throughout the renal tubules, but the majority of it occurs in the PCT.
- It is actively transported from the tubular lumen into the tubule cells by sodium-potassium ATPase pumps on the basolateral membrane.
- This creates a sodium concentration gradient that drives the passive reabsorption of other substances, such as glucose and amino acids, through cotransporters.
Conclusion:
In summary, substances like glucose, amino acids, and sodium are actively reabsorbed in the renal tubules. This is contrary to the statement provided, which incorrectly states that these substances are always reabsorbed passively. Tubular reabsorption is a highly regulated process that ensures the retention of essential substances and the elimination of waste products.
Which of the following statements is incorrect w.r.t tubular reabsorp...
Glucose and amino acids are reabsorbed actively.
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