# Protein Transport ## Types of Transport ### Active vs Passive Transport > See also: > - [[Diffusion and Osmosis]] uses an energy source to transport molecules against a concentration gradient (low → high) cell mobility is often powered by [[proteins]] **Uniporter:** mycolone direction **Symporter:** multiple in the same direction **Antiporter:** ### Cotranslational vs Posttranslational Translocation Translation is coupled to translocation for most eukary **Posttranslational Translocation** - Proceeds independently of both ribosomes and SRP - It is used extensively in yeast, but is less common in higher eukaryotes except for the smallest of proteins - The associated translocon is distinct in composition, but they share the same channel ![[Pasted image 20250422115031.png]] ## Protein Signal Sequences The accurate transport of proteins requires organelle-specific **signal sequences**. These sequences are discrete stretches of amino acids wtihin a protein’s primary structure that are recognized by machinery associated with the target organelle. ## Membrane Targeting ### Transmembrane Protein Integration --- ### ATP-Binding Cassette (ABC) Transporter Moves things in one direction (uniporter) Primary Active Transporter