Polar groups like O-H and N-H are also important for binding dyes to fibers (see Pigments & Dyes.). In that case, the protein albumin is denatured from a clear viscous liquid to produce a white solid. When this bonding network is disrupted, the proteins are said to be denatured, which is the process that takes place when eggs are cooked. The long chains of amino acids fold and coil in such a way as to give a very well-defined structure that is crucial to the function of the protein, and this structure is held in place largely by hydrogen bonding. O are important in determining and stabilizing the protein structure.Hydrogen bonding is also important for proteins where hydrogen bonds involving -O-H These hydrogen-bonding interactions hold the cellulose molecules together in a more rigid structure than would be possible otherwise. The unique properties of water are due in large part to hydrogen bonding between the water molecules. In aqueous solution, these hydrogen atoms are constantly exchanging with each other and the the hydrogen atoms of the water. They are stronger than many other types of dipole-dipole forces, and hydrogen bonds become a facile way for hydrogen to be transferred from one molecule to another. This creates a slight dipole moment that allows that hydrogen to be attracted to electronegative atoms possessing lone pairs of electrons, and these interactions can be both intramolecular and intermolecular. Whenever hydrogen atoms are attached to an electronegative atom such as oxygen, nitrogen or fluorine, that hydrogen becomes slightly positively charged. This gives rise to the possibility of hydrogen-bonding. One of the important features of the cellulose polymer is the presence of numerous -O-H groups along the chain. Putting glucose into glycogen is how the body stores glucose in a compact form. Glycogen contains branched polymers of glucose attached to a central protein core called glycogenin. Another commonly encountered polymer of glucose is glycogen. The straight chain form of starch is called amylose and the branched form is amylose pectin. Additionally, the glucose polymer in starch may have branches created by attaching additional glucose molecules along the sides of the chain. Starch is water soluble but cellulose is not, consequently starch can be digested but not cellulose. While this seems like a very minor change in structure, it has a major impact on the properties of the two molecules.
If one examines the α and β forms of glucose in the figures below, one will see that the -OH group on the carbon adjacent to the oxygen atom in the ring and the -CH 2OH groups are on opposite sides of the ring in α-D-glucose but are on the same side of the ring in β-D-glucose. In starch, they connect via α linkages while those in cellulose are the β form. Cellulose is related to starch, which is also a polymer of glucose, but the glucose molecules in the chains are slightly different. Image from Mamichaelraj, CC BY-SA 4.0, via Wikimedia Commons.Ĭellulose is a polymer of glucose that forms fibers providing structural stiffness for plants and trees. Polymers may form in straight chains, but in some cases they can also be branched, meaning that they have side polymers that fork off at various points along the main chain.Ī cotton plant ready for harvest. Proteins are polymers composed of the 20 different naturally-occurring amino acids, and the amino-acid sequence is critical to determining the function of the molecule.
Different monomers can be polymerized in segments to give block copolymers, - x- y- z-, etc. If more than one type of monomer is present, the polymer can have a regular repeating of the monomers such as -A-B-A-B-A-B- etc., or they can be connected randomly: -A-B-B-B-A-A-B-A-A-, etc. A polymer can be made up of a single monomer (here labelled A or B), or the polymer can be made up of more than one type of monomer. There is a limitless variety in the way polymers are put together. Polymers are long strings of small organic molecules, known as monomers, that are connected end-to-end to produce very long covalently-bound strands. Whether naturally-occurring or man-made, these fibers are made up of polymers. All textiles and paper are based on molecules that can be combined to form fibers.
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