16.4 Polymers and Biopolymers | High School Chemistry

This paragraph introduces the concept of polymers, which are long chains of repeating, similar or identical molecules, and their significance in chemistry, particularly in the creation of plastics like polyvinyl chloride (PVC) and styrofoam. It distinguishes between addition polymers, formed from identical subunits, and condensation polymers, which involve the formation of small molecules like water. The paragraph also previews three types of biopolymers: proteins, carbohydrates, and nucleic acids, which are essential components within living organisms.

The second paragraph delves into the specifics of polymerization reactions. It explains how addition polymers are formed from alkenes through a process that involves breaking the double bond and creating new bonds with adjacent molecules, facilitated by an initiator. The paragraph provides polyvinyl chloride as an example of an addition polymer. It then contrasts this with condensation polymers, which result in the release of small molecules, typically water, during the reaction between different monomers, such as an alcohol and a carboxylic acid. The formation of a copolymer from these different monomers is also discussed.

This paragraph focuses on proteins, which are condensation polymers made up of amino acids. Amino acids are characterized by the presence of an amine and a carboxylic acid group, and their polymerization results in the formation of peptide bonds. The paragraph highlights the importance of the sequence of amino acids in determining the protein's three-dimensional structure, which is crucial for its function in the body. It also touches on the role of enzymes, which are proteins acting as catalysts for biochemical reactions.

The fourth paragraph explores carbohydrates, starting with monosaccharides like glucose, which can form rings and exist in different isomeric forms. It discusses how monosaccharides can link to form disaccharides, such as sucrose, and polymerize into polysaccharides like starch and glycogen. Starch is highlighted as a storage form of glucose in plants, while glycogen serves a similar purpose in animals. The paragraph also mentions cellulose, a glucose polymer in plant cell walls that humans cannot digest, thus functioning as dietary fiber.

The final paragraph discusses nucleic acids, DNA and RNA, which are composed of a sugar (ribose in RNA and deoxyribose in DNA), a phosphate group, and a nitrogenous base. It explains that the sequence of these bases in DNA and RNA is responsible for storing and transmitting genetic information. DNA is depicted as a double helix with complementary base pairing, while RNA is portrayed as a single strand involved in protein synthesis. The paragraph emphasizes the uniqueness of nucleic acids and their critical role in the central dogma of molecular biology.