Transporter proteins transport solutes across the membrane via which of the following mechanisms?

• A. Conformational changes that move the solute across the membrane
• B. Formation of open pores that allow free diffusion
• C. Passive diffusion through the lipid bilayer
• D. Direct hydrolysis of ATP at the membrane surface

Answer: (A)

Verified step by step guidance

1. Understand the role of transporter proteins: Transporter proteins are integral membrane proteins that facilitate the movement of specific solutes across the lipid bilayer. They are highly selective and often require specific mechanisms to function.
2. Eliminate incorrect options: Passive diffusion through the lipid bilayer does not involve transporter proteins. Instead, it refers to the movement of small, nonpolar molecules directly through the lipid bilayer without assistance.
3. Analyze the mechanism of open pores: Formation of open pores that allow free diffusion is characteristic of channel proteins, not transporter proteins. Transporter proteins do not create open pores but instead undergo conformational changes.
4. Consider the role of ATP hydrolysis: Direct hydrolysis of ATP at the membrane surface is a feature of ATP-driven pumps (a type of active transport), but not all transporter proteins rely on ATP hydrolysis. Some work via facilitated diffusion without energy input.
5. Identify the correct mechanism: Transporter proteins operate by undergoing conformational changes that move the solute across the membrane. This mechanism ensures specificity and controlled transport of solutes.