Membrane Transport Proteins (Overview)

MEMBRANE TRANSPORT PROTEINS
Allow molecules to cross the membrane faster and more efficiently than simple diffusion
i. Channels: form open pores in the membrane
ii. Transporters: undergo conformational changes during transport

• Solute binds solute binding site
• Binding produces conformational change in protein
• Solute leaves transporter (release facilitated by conformational change)

TWO TYPES OF TRANSPORT ACROSS MEMBRANES

Passive transport

• Molecules move down their electrochemical gradient
• No energy is required

Active transport

• Molecules move against their concentration gradient
• Energy is required

ELECTROCHEMICAL GRADIENT
Accounts for voltage across the membrane (electro-) and concentration gradient (chemical)