- · Most macromolecules are polymers. Carbohydrates, lipids, proteins, and nucleic acids are the 4 major classes of organic compounds in cells. Some of these compounds are very large and are called macromolecules. Most macromolecules are polymers, chains of identical or similar building blocks called monomers.
- · Monomers form larger molecules by condensation reactions in which water molecules are removedèdehydration
- · Polymers can disassemble by the reverse process, hydrolysis èaddition of water breaks monomers apart)
- · An immense variety of polymers can be built from a small set of monomers (pp. 63-64) Each class of polymer is formed from a specific set of monomers. Although organisms share the same limited number of monomer types, each organism is unique because of the specific arrangement of monomers into polymers.
Carbohydrates:fuel & building material
· Sugars, the smallest carbohydrates, serve as fuel and carbon sources. Monosaccharides are the simplest carbohydrates. They are used directly for fuel, converted to other types of organic molecules, or used as monomers for polymers. Disaccharides consist of two monosaccharides connected by a glycosidic linkage.
- · Carbohydrates are of two types
- o 1) simple èmonosaccharides (singles sugars), disaccharides (2 sugars , oligosaccharides (8-10 sugars) or 2)complex (polysaccharides)
- · Polysaccharides, the polymers of sugars, have storage and structural roles. The monosaccharide monomers of polysaccharides are connected by glycosidic linkages. Starch in plants and glycogen in animals are both storage polymers of glucose. Cellulose is an important structural polymer of glucose in plant cell walls. Starch, glycogen, and cellulose differ in the positions and orientations of their glycosidic linkages.
- · The building blocks (monomers) of carbohydrates are simple sugars.
lipids-diverse hydrophobic Molcules
- · Fats store large amounts of energy. Fats, also known as triacylglycerols, are constructed by the joining of a glycerol molecule to three fatty acids by dehydration reactions. Saturated fatty acids have the maximum number of hydrogen atoms (Ex. Lard, waxes, beef fat butter). Unsaturated fatty acids (present in oils) have one or more double bonds in their hydrocarbon chains.
- · Two Types of FATS based on their fatty acid compositionè1)Saturated (tend to be solid at room temperature, more resistant to burning, more resistant to bacterial/fungal decomposition)and 2)Unsaturated (tend to be liquid at room temperature, less resistant to burning)
- · Fats unlike proteins, carbohydrates or nucleic acids are NOT polymers.
- · Phospholipids are major components of cell membranes. Where fats have a third fatty acid linked to glycerol, phospholipids have a negatively charged phosphate group, which may be joined, in turn, to another small hydrophilic molecule. Thus, the "head" of a phospholipid is hydrophilic.
- · Steroids include cholesterol and certain hormones. Steroids have a basic structure of four fused rings of carbon atoms.
- · A protein consists of one or more polypeptide chains folded into a specific three-dimensional conformation (p. 71).
- · A polypeptide is a polymer of amino acids connected in a specific sequence .
- · Proteins have many functions. These amino acids have specific properties based on their R groups. Polypeptides are constructed from 20 different amino acids, each with a characteristic side chain (R group).
- · The carboxyl and amino groups of adjacent amino acids link together in peptide bonds.
- o A protein’s function depends on its specific conformation.
- o The primary structure of a protein is its unique sequence of amino acids. Protein shape is ultimately determined by its primary structure.
- o Secondary structure is the folding or coiling of the polypeptide into repeating configurations, mainly the a helix and the b pleated sheet, which result from hydrogen bonding between parts of the polypeptide backbone.
- o Tertiary structure is the overall three-dimensional shape of a polypeptide and results from interactions between amino acid side chains.
- o Proteins made of more than one polypeptide chain (subunits) have a quaternary level of structure. The structure and function of a protein are sensitive to physical and chemical conditions.