One Small Region of a Human Kidney Tubule Known as the Thick

question 83

Multiple Choice

One small region of a human kidney tubule known as the thick ascending limb (or TAL) has tight junctions that are permeable to magnesium (Mg²⁺) ions. What is thought to account for the permeability of this tight junction to magnesium ions?

• A)The membrane in this region is leaky because of special phospholipids.
• B)Loops of claudin molecules that extend into the extracellular space form pores in the TAL.
• C)Loops of claudin molecules that extend into the cytoplasm form pores in the TAL.
• D)Loops of claudin molecules fully embedded in the TAL membrane form pores in the TAL.
• E)Claudin molecules form gap junctions that allow the passage of magnesium ions.

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