14: Biological Polymers
- Page ID
- 341978
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- 14.1: Carbohydrates
- All carbohydrates consist of carbon, hydrogen, and oxygen atoms and are polyhydroxy aldehydes or ketones or are compounds that can be broken down to form such compounds. Examples of carbohydrates include starch, fiber, the sweet-tasting compounds called sugars, and structural materials such as cellulose. The term carbohydrate had its origin in a misinterpretation of the molecular formulas of many of these substances.
- 14.2: Carbohydrates- Monosaccharides
- Last time we learned how a chiral compound's absolute configuration can be described by the R/S naming system. We also considered the situations which can arise when a compound has two (or more) stereogenic carbons. Our examples for that were in fact sugars; monosaccharide aldotetroses. We'll begin by making some structural sense of those terms.
- 14.3: Glycosides, Disaccharides, Polysaccharides
- Today we'll look in more detail at the chemistry of that hemiacetal linkage. In particular, we'll recall how hemiacetals are converted to acetals. We'll find that these acetal linkages are what holds di- and polysaccharides together.
- 14.4: Starch and Cellulose
- The polysaccharides are the most abundant carbohydrates in nature and serve a variety of functions, such as energy storage or as components of plant cell walls. Polysaccharides are very large polymers composed of tens to thousands of monosaccharides joined together by glycosidic linkages. The three most abundant polysaccharides are starch, glycogen, and cellulose. These three are referred to as homopolymers because each yields only one type of monosaccharide (glucose) after complete hydrolysis.
- 14.5: Amino Acids
- The proteins in all living species are constructed from the same set of 20 amino acids, so called because each contains an amino group attached to a carboxylic acid. The amino acids in proteins are α-amino acids, which means the amino group is attached to the α-carbon of the carboxylic acid. Humans can synthesize only about half of the needed amino acids; the remainder must be obtained from the diet and are known as essential amino acids.
- 14.6: Peptides
- The amino group of one amino acid can react with the carboxyl group on another amino acid to form a peptide bond that links the two amino acids together. Additional amino acids can be added on through the formation of addition peptide (amide) bonds. A sequence of amino acids in a peptide or protein is written with the N-terminal amino acid first and the C-terminal amino acid at the end (writing left to right).
- 14.7: Polypeptides and Proteins
- Amino acids are the building blocks for proteins. There are 20 different amino acids commonly found in proteins. All amino acids contain an amino group and a carboxyl (acid) group. To form polypeptides and proteins, amino acids are joined together by peptide bonds, in which the amino of one amino acid bonds to the carboxyl (acid) group of another amino acid. A peptide is two or more amino acids joined together by peptide bonds. Proteins are long chains of amino acids held by peptide bonds.