While traveling through the rain forests of Peru, you are introduced to a rare and exotic plant. You discover that it contains a toxin that blocks the reabsorption of sodium ions from the proximal tubule. If administered, what affect would this toxin have on the reabsorption of water and other electrolytes?
a. The toxin would significantly increase the amount of water absorbed and the electrical gradient for reabsorbing chloride.
b. The toxin would significantly decrease the amount of water and certain electrolytes reabsorbed by the proximal tubule.
c. The toxin would significantly increase the amount of water and calcium ions reabsorbed by the proximal tubule.
d. The toxin would significantly decrease the amount of water reabsorbed but would significantly increase the number of other electrolytes reabsorbed by the proximal tubule.

C. The toxin will significantly decrease the amount of water and certain electrolytes reabsorbed by the proximal tubule.

Explanation: Reabsorption takes place majorly in the proximal convoluted tubule of the nephron. Mostly all water, glucose, potassium, amino acids are lost during glomerular filtration.

A factor that increasingly affects reabsorption and urinary excretion is urine pH, mostly in the case with weak electrolytes. Weak acids are more ionized and excretion is higher when the urine is alkaline. Weak acids are less ionized if the urine is acidic and will undergo reabsorption causing renal excretion to reduced. The urinary excretion rates of weak electrolytes vary because urinary PH varies in humans.

When a toxin that blocks reabsorption of sodium ions from the proximal tubule is administered, as a result substance are ionized in and remain in urine which decreases the amount of water and some electrolytes reabsorbed in the proximal tubule.

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