8/26/09 Biological Macromolecules Large molecules unique to living organisms Include: * Carbohydrates * Lipids * Nucleic Acids * Proteins Central properties of macromolecules 20 elements found in living organisms 6 found in high amounts: C, H, O, P, S, N Joined by chemical bonds: Covalent bonds are strong (ex. H2, NH3); formed and broken by enzymes Non-covalent bonds are weak example hydrogen bonds exist between hydrogen and a more electronegative element (ex. O, N). Presence of many H-bonds within and between macromolecules enhances stability of entire structure. Formed and broken spontaneously. Made up of monomers or monomeric subunits Subunits may be connected to each other by covalent and/or non-covalent bonds Polymers made up of similar or identical monomers ex. Starch-glucose monomers; proteins-amino acid monomers Carbohydrates Also known as sugars or polysaccharides; act as energy source; constituent of cell wall; subunits connected by covalent bonds Gylcosidic bonds to form: Disaccharides (2) Trisaccharides (3) Polysaccharides (>50) The Lipids Relatively insoluble in water or aqueous environments; soluble in non-polar organic solvents (ex. Ether, benzene) Important energy source and constituent of plasma membranes Most lipids contain Fatty Acids Simple fat = glycerol + fatty acids Complex fat = simple-fat + additional compounds (ex. PO4, N, ect.) Steriods- Cholesterol-like fats Nucleic Acids Made up o nucleotide monomers Polymers are RNA and DNA Proteins Made up of amino acid monomers connected by covalent peptide bond. Most (NOT ALL) known enzymes are proteins. Proteins are highly folded molecules (specific shape and structure). This structure defines function of individual proteins. Proteins also form important structural components of cells (ex. Eukaryotic cytoskeleton) There are up to 4 different levels of organization in protein structure: Primary Structure: Linear order of amino acids Secondary Structure: Shape along single axis Tertiary Structure: 3D organization of the individual secondary structures. Quaternary structure: occurs when a protein has more than 1 sub-unit. Shows how subunits associate with each other. All proteins have primary, secondary, and tertiary structures. Only those with 2 or more sub-units posses quaternary structure. Secondary, tertiary, and quaternary structures are primarily stabilized by non-covalent bonds. Thus, the shape of proteins is relatively flexible.
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