Biological Molecules

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General Characteristics of Biological Molecules Carbon based Interact by means of functional groups Assembled or disassembled by adding or removing water

Carbon and Biological Molecules Able to form 4 stable bonds Organic Compounds – contain carbon Few inorganic compounds contain carbon C

Functional Groups Group with distinct chemical properties Carbon is skeleton holding groups of atoms Chemical reactions within organisms involve transfer of a functional group Macromolecules –many functional groups

Changing Molecules Assembling molecules –Growth and repair –Producing molecules essential for chemical reactions to take place Disassembling molecules –Digestion –Providing molecules that can enter cells

Assembly: Dehydration Synthesis Monomers = building blocks Monomers are linked with covalent bonds Polymers = chain-like molecules

Dehydration Synthesis One molecule of water is removed Two monomers are joined –One loses hydroxyl group –Other loses hydrogen

Disassembly: Hydrolysis Hydrolysis is opposite of dehydration Covalent bonds broken with addition of H 2 O Energy in bond is released

Major Classes of Biological Molecules

Carbohydrates Contain C,H, & O H:O = 2:1 Primary role is for energy Breaking bonds releases energy Glucose

Carbohydrate Example: Glucose

Monosaccharides Simplest carbohydrates Individual sugar molecules

Disaccharide Monosaccharides linked together Less readily broken during transport

Polysaccharides Long polymers of sugars Insoluble Called complex carbohydrates

Common Polysaccharides Starches –Stored energy in plants Glycogen –Animal energy storage

Some Carbohydrates are Used for Structure Cellulose – plant cell wall material Chitin – in insects, fungi

Lipids H:O ratio higher than 2:1 Not dissolved in water Categories of lipids –Oils, fats & waxes –Phospholipids –steroids

Fats Non-polar & insoluble Work well for storage More energy than equivalent carbohydrates Two types of subunits –Glycerol –Fatty acids

Triglyceride Molecule with 3 fatty acids Includes most dietary fat

Triglycerides Saturated – carries as many H as possible

Triglycerides Unsaturated – double bond replaces H Polyunsaturated – more than 1 double bond

Differences in Fats & Oils Polyunsaturated –Plant oils –Fish oils Saturated –Animal fats There are exceptions

Waxes Chemical backbone differs from fats & oils One carbon chain Water resistant

Phospholipids Phosphate group replaces a fatty acid Key component of cell membrane

Steroids With 4 carbon rings Important for membranes

Proteins Transport other molecules Provide for muscle contraction Help protect body Play role in nerve transmission Control growth Serve as enzymes Act as chemical messenger

Protein Structure Chain of amino acids Polypeptide bond

Protein Synthesis & Hydrolysis

Protein Levels of Structure Primary structure = amino acid sequence Secondary structure = shape –Coils –Folds Tertiary structure = complex shape caused by hydrogen bonds

Protein Function Dependent upon 3-dimensional structure Can be degraded by heat

Nucleic Acids Composed of nucleotides Stores information

Forms of Nucleic Acid DNA = deoxyribonucleic acid RNA = ribonucleic acid

End Chapter 4