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Multiple Choice
Which of the following statements is true regarding the sodium-glucose transport protein (SGLT)?
A
SGLT only functions when sodium ions are absent from the extracellular fluid.
B
SGLT transports glucose into cells by coupling its movement with sodium ions via secondary active transport.
C
SGLT uses ATP directly to transport glucose across the membrane.
D
SGLT is responsible for exporting glucose out of the cell into the bloodstream.
Verified step by step guidance
1
Understand the role of the sodium-glucose transport protein (SGLT): SGLT is a type of symporter that moves glucose into cells by coupling its transport with sodium ions. This process is an example of secondary active transport, which relies on the sodium gradient established by the sodium-potassium pump.
Clarify the concept of secondary active transport: Unlike primary active transport, which directly uses ATP, secondary active transport uses the energy stored in the electrochemical gradient of one molecule (in this case, sodium ions) to drive the movement of another molecule (glucose).
Evaluate the first statement: 'SGLT only functions when sodium ions are absent from the extracellular fluid.' This is incorrect because SGLT requires sodium ions in the extracellular fluid to function, as the sodium gradient is essential for glucose transport.
Evaluate the second statement: 'SGLT transports glucose into cells by coupling its movement with sodium ions via secondary active transport.' This is correct because SGLT uses the sodium gradient to move glucose into the cell against its concentration gradient.
Evaluate the remaining statements: 'SGLT uses ATP directly to transport glucose across the membrane' is incorrect because SGLT does not directly use ATP. 'SGLT is responsible for exporting glucose out of the cell into the bloodstream' is also incorrect because SGLT imports glucose into the cell, not exports it.