Porins and Aquaporins

Porins

• Form pores on the outer membranes of the mitochondria.
• Pores are very large.
• Less specific than ion channels.
• Allow larger substances to move through.
• Allow more than one type of molecule to pass through.

Aquaporins

• Allow water to move through them.
• Enable rapid water transport.
• Found in the kidneys, specifically in the proximal convoluted tubules.
• The kidneys filter blood, removing fluid and waste.
• Most of the filtered water (approximately 99%) is reabsorbed back into the bloodstream.
• Aquaporins facilitate the quick movement of water during reabsorption.
• Tetrameric integral membrane proteins: Composed of four polypeptide subunits.
• Transmembrane proteins: Span both layers of the cell membrane, enabling transport across the membrane.
• Channel proteins and carrier proteins must be transmembrane proteins to function effectively.