BIOL 1012 Lecture Notes - Lecture 12: Lipid Bilayer, Passive Transport, Dynamic Equilibrium
17 Feb 2017
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Document Summary
Membranes are fluid mosaics of lipids and proteins with many functions: biologists use the fluid mosaic model to describe membrane structure, the plasma membrane exhibits selective permeability, the proteins embedded in the phospholipid bilayer perform various functions. Types of proteins on cell: transport proteins. Allow specific ions or molecules to enter or exit the cell: enzymes. Carry out sequential reactions: attachment proteins. Help support the membrane: receptor proteins. Relay messages by activating other molecules inside cell: junction proteins. Form intercellular junctions and attach to adjacent cells: glycoproteins. Serve as id tags, can be recognized by other cells. The spontaneous formation of membranes was a critical step in the origin of life: phospholipids spontaneously assemble into simple membranes. Passive transport is diffusion with no energy investment: diffusion: the tendency of particles to spread out evenly in available space. Eventually reach dynamic equilibrium: diffusion across cell membrane requires no energy (passive transport)
