Protein Structure and Protein Denaturation [HD Animation]


this familiar Gelatin dessert actually is a good example of the process of coagulation of proteins into a three-dimensional lattice work that Entraps water molecules to produce a semi solid gel This animation explains the physical chemistry behind the process Proteins are synthesized by polymerizing amino acids The polymerization occurs by repeatedly forming peptide bonds that link individual amino acids together into a chain There are three structural features that influence the three-dimensional shape of a water soluble protein Primary structure is the peptide bond between individual amino acids that creates a long chain of connected Amino acids? these long chains of polymerized Amino acids have hydrophobic water repelling and Hydrophilic water Attracting projections that are oriented perpendicular to the chain as shown [in] this illustration of a growing protein chain Secondary structure is the helix that the protein chain curls into as a result of hydrogen bonds and other weak forces tertiary structure is created when the protein molecules fold back on themselves outside of the helical segments to put the hydrophobic portions to the interior and the Hydrophilic portions to the exterior Several helical regions can exist in different portions of the molecule When the protein has folded and refolded to reach its most stable configuration It will have mostly hydrophilic amino acid residues on the exterior and mostly Hydrophobic residues directed into the interior when natural proteins are subjected to physical or chemical treatment their structure changes and they become Unnatural we call that process Denaturation in this example heating the proteins in Solution Imparts energy to the protein molecules this added energy is enough to break the relatively weak forces that hold the protein in its refolded and helical tertiary and Secondary configurations as The process of denaturation proceeds the protein molecule unfolds more and more and the internally directed hydrophobic regions now become exposed on the outside of the molecule The Peptide bonds are largely hydrophilic once these segments are set free from each other They attract water molecules The recruitment of water Molecules Entraps the water molecules in close proximity to the protein strands the Hydrophobic portions of the Molecules are also exposed This situation is unfavored because the hydrophobic portions of Molecules are not stable in an aqueous environment Hence upon unfolding the hydrophobic regions on individual protein Molecules will associate with hydrophobic regions on other protein molecules This situation encourages the association of these protein molecules into larger and larger Random three-dimensional structures the Molecules aggregate into very large water insoluble collections that are quite randomly assembled as the proteins denature Latticework structures grow amorphous [Lee] and attract the solvent water Molecules into cell-like structures the self associated water molecules in groups adhere to the surface of hydrophilic regions of the protein while hydrophobic regions of the protein dissolve into each other and provide the energy to retain the structure as this process continues Irreversibly all of the protein Molecules are recruited to this large and soluble mass in a randomly organized structural framework that contains entrapped water molecules One example of the consequences of unfolding and reassociate nKrumah [Liqu] [eul’s] is coagulation of egg white Frying an egg is no more complicated than denaturing the egg white protein the assembly of irreversibly denatured protein Molecules results in formation of a solid gel The gel and traps water molecules inside the white into a semi solid structure which holds its shape under normal conditions Other examples of denatured protein assembling into three-dimensional structures include the baking of yeast risen bread Coagulation of meat proteins by cooking in such products as hot dogs and in the solidification of Gelatin upon cooling of a solute Denaturation and coagulation of proteins is a complex irreversible process But the study of denaturation has allowed [us] to better understand the three-dimensional structure of native proteins

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