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Molecules of Life Molecules of Life • Carbohydrates – monosaccharides – energy supply • Proteins – amino acids – structural components • Lipids – fatty acids – structural components, energy, hormones • Nucleic acids – nucleotides – DNA-genetic material Composition of Molecules of Life most are carbon based • • organic compounds • unique to living systems – with exception of CO2 & carbides • carbon is necessary for life • electroneutral – never loses or gains electrons – always shares or forms covalent bonds Covalent Bonding • carbon can form 4 covalent bonds with other elements or with itself – has 4 electrons in outermost shell • makes each carbon atom a connecting point from which another molecule can branch in four directions H | H--C--H | H Covalent Bonding • since carbon can bind to itself • has capacity to construct endless numbers of carbon skeletons varying in size & branching patterns Organic Compounds • chain of carbons in organic molecule is-carbon skeleton • branched or unbranched • double or single bonds • straight or arranged in ring form • each has unique 3-D shape • properties depend on carbon skeleton & on atoms attached to skeleton • groups of atoms participating in chemical reactions are functional groups H | C ||| C | H Functional Groups • OH- (hydroxyl) • C=O (carbonyl) • COOH (carboxyl) • NH2 (amino) • SH-sulfhydryl group • PO3 (phosphate) Phosphate group Classes of Molecules & Functional Groups • COOH & NH2- amino acids • hydroxyl groups-alcohols • carboxyl groupscarboxylic acids-acetic acid • sugars contain bothcarbonyl group & several hydroxyl groups • phosphate groups-found on nucleic acids Macromolecules • 4 main classes – macromolecules or polymers • consist of many identical or similar molecular units strung together – monomers • cells link monomers in anabolic reactions by dehydration synthesis – chemical reaction which removes water • broken down into constituent monomers by adding water – catabolic reactionshydrolysis Carbohydrates • composed of C, H & O • 1:2:1 ratio • Formula: (CH2O)n should give formula for any carbohydrate • may contain nitrogen, phosphate and/or sulfur • Monomers-monosaccharides – simple sugars – building blocks for all other carbohydrates • 2-10 monosaccharides form oligosaccharide • hundreds- polysaccharide. • hydrophilic – water loving • larger molecules are less soluble in water Glucose Monosaccharides • simple sugars • single chain or ring of 3-7 carbons • named for number of carbons they contain • 5 carbons-pentoses • 6 carbons-hexoses • glucose contains 6 carbons-hexose • formula-C6H1206 – most important metabolic fuel in body – broken downATP + CO2 • fructose-6 carbon monosaccharide • same formula as glucose • fructose & glucose are isomers – chemical compounds with same molecular formula but with elements arranged in different configurations • Galactose-isomer of glucose & fructose Glucose Galactose Fructose • • • • • • • • Disaccharides double sugars covalent bond- between hydroxyl groups of two simple sugars physiologically important disaccharides Sucrose – sugar cane & sugar beets – Glucose + fructosesucrose + H2O Lactose-found in milk of mammals – disaccharide of galactose & glucose Maltose – major degradation product of starch – composed of 2 glucose monomers Disaccharides-too large to pass through cell membranes must be broken down into constituent parts by hydrolysis Sucrose + H20 glucose + fructose. • • • • • • • Polysaccharides complex carbohydrates dehydration synthesis reactions add more monosaccharides polysaccharides most carbohydrates in nature are in this form fairly insoluble – make perfect storage molecules Glycogen – major stored carbohydrate in animal liver & muscle cells – highly branched at about every 8-10 residues Starch – major form of stored carbohydrate in plants – Structure-identical to glycogen-less branching at every 20-30 residues Cellulose – found in plants – most abundant compound on earth – cannot be digested by humans Lipids • contain mostly C & H • 1:2 ratio • also contain oxygen but less than carbohydrates • often have N, S & phosphorous • hydrophobic – do not dissolve in water • include neutral fats, phospholipids & steroids Lipid Functions • physiologically important lipids have 4 major functions • structural components of biological membranes – cholesterol, phospholipids and glycolipids help form and maintain intracellular structures • energy reserves – provide 2X as much energy as carbohydrates • hormones & vitamins are a type of lipid-steroids • lipophilic bile acids – important for lipid solubilization Lipids • composed of fatty acids & glycerol (an alcohol) • fatty acids-long-chain hydrocarbon molecules hydrocarbon chains make lipids nonpolar and therefore insoluble in water fat synthesis involves attaching 3 fatty acid chains to one glycerol by dehydration synthesis-producing triglycerides glycerol is always the same; fatty acid composition varies length of neutral fat’s fatty acid chains & degree of saturation determine how solid a fat is at room temperature saturated – fatty acids with no carbon to carbon double bonds unsaturated – have double bonds monounsaturated fats have one unsaturated bond polyunsaturated fats have multiple unsaturated bonds double bonds make for lower melting points presence of unsaturated fatty acids makes fat liquid at room temperature • • • • • • • • • • Hydrolysis of Triglycerides • Hydrolysis breaks triglycerides • fatty acid + glycerol Steroids • large lipid molecules with carbon skeleton bent into 4 rings • most important one-cholesterol • obtained by absorption from animal products in diet – meat, cream & egg yolks • • • • can also be made by the body absolutely essential for life component of cell membranes raw material for Vitamin D, steroid hormones and bile salt synthesis • without cholesterol there would be no steroid hormones such as estrogen and testosterone and therefore no reproduction • without corticosteroids we would die Proteins • C, H, O, N & small amounts of S & sometimes phosphorous • monomer-amino acids • 1-7 amino acids form peptide • up to 100 form polypeptide • more than 100 comprise a protein • • • • • • • • • • • Proteins most abundant organic compounds in human body provide support for cells, tissues & organs and create a 3-D framework for body contractile proteins allow for movement via muscle contractions transport proteins carry insoluble lipids, respiratory gases & minerals in blood serve as buffers; help to prevent dangerous pH changes enzymes are proteins important in metabolic regulation – needed to speed rate of chemical reactions protein hormones coordinate, control & influence metabolic activities of nearly every cell important for defense skin, hair, & nails protect underlying tissues from environment antibodies protect us from disease clotting proteins protect from us from bleeding out Amino Acids • • • • • • • • 20 amino acids (excluding proline) contain carboxylic acidCOOH & amino-NH2 or amine group functional groups are attached to same carbon atom R group attaches to same carbon amino acid is distinguished by its particular R-group 2 broad classes based upon whether Rgroup is hydrophobic or hydrophilic hydrophobic repel aqueous environments – reside predominantly in interior of proteins hydrophilic amino acids interact with aqueous environments & often form Hbonds – found predominantly on exterior of proteins Protein Structure • each protein contains unique sequence of amino acids • four levels of protein structure • Primary • Secondary • Tertiary • Quaternary Structure & Function • structure determines function • shape of protein allows it to carry out specific duties • proteins whose job is to fill in a space (active site) on another molecule are globular in shape • those that make up something like muscles or tendons are fibrous • shapes depend on environmental characteristics – ionic composition, pH & temperature • non homeostatic change in any of these will denature protein • denaturation causes protein to lose shape • loss of shapecannot function properly Nucleic Acids • • • • • • • largest, organic molecules in body C, H, O, N, & phosphorous consists of long stretches of nucleotides – monomer for nucleic acids provide directions for building proteins 2 main types RNA – translates DNA code DNA – contains genetic information that is inherited from our parents Nucleic Acids • RNA –single polynucleotide chain • DNA –double helix form –two polynucleotide chains wrapped around one another Nucleic Acids • exist in mono-, di-, & triphosphorylated forms • often abbreviated to AMP • Mono, Di- & tri-phosphorylated forms of adenosine are abbreviated AMP, ADP & ATP • phosphate bonds are high energy bonds – meaning they contain energy – When broken they yield 7kcals • ATP ADP + Pi + energy • ATP is energy currency of all cells
