BIO 1140 Study Guide - Treadmilling, Actomyosin Ring, Endoplasmic Reticulum
Document Summary
Organized into higher order structures forming bundles or 3d networks with properties of semisolid gels. Particularly abundant beneath the plasma membrane where they form a network to provide mechanical support, determine cell shape, allow movement of cell surface. Extremely abundant in all types of eukaryotic cells. Mammals have at least 6 actin genes. 4 in different types of muscle, 2 in nonmuscle cells. Monomer is g actin which polymerizes to form filaments, f actin. Have distinct polarity, plus and minus end. In low ionic strength, actin filaments depolymerize to monomers, and polymerize spontaneously if ionic strength is increased. First step in polymerization is called nucleation, and is the formation of an aggregate of 3 actin monomers. end. Filaments then grow on both ends, but the plus end elongates 5-10 times faster than the minus. Actin monomers bind atp which is hydrolyzed to adp. Actin monomers bound to atp polymerize more readily than those to which adp is bound.
