Multiple Choice
In the context of principles of transmembrane transport, what are the two main types of active transport across cellular membranes?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In the context of principles of transmembrane transport, which process does NOT require direct energy input from the cell (e.g., ATP hydrolysis)?
A
Transport of protons () against their electrochemical gradient by a proton pump
B
Secondary active transport of glucose into intestinal epithelial cells via the -glucose symporter (SGLT)
C
Facilitated diffusion of glucose through a GLUT transporter down its concentration gradient
D
Primary active transport of and by the /-ATPase
Verified step by step guidance1
Step 1: Understand the types of transmembrane transport processes. There are three main types: passive transport (including facilitated diffusion), primary active transport, and secondary active transport.
Step 2: Recall that passive transport, such as facilitated diffusion, moves molecules down their concentration gradient and does NOT require direct energy input like ATP hydrolysis.
Step 3: Recognize that primary active transport uses ATP directly to move ions against their electrochemical gradients, such as the Na+/K+-ATPase and proton pumps.
Step 4: Understand that secondary active transport uses the energy stored in ion gradients (created by primary active transport) to move other molecules against their gradients, like the Na+-glucose symporter, but does not use ATP directly at the transport step.
Step 5: Conclude that among the options, facilitated diffusion of glucose through a GLUT transporter down its concentration gradient is the process that does NOT require direct energy input from the cell.
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