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Transcript
THE STRUCTURE AND FUNCTION OF MACROMOLECULES POLYMERS • POLYMERS- large molecules consisting of many identical or similar subunits connected together • MONOMER- subunits of polymers • MACROMOLECULES- large organic polymer FOUR CLASSES OF MACROMOLECULES • CARBOHYDRATES • LIPIDS • PROTEINS • NUCLEIC ACIDS HOW MACROMOLECULES ARE MADE • POLYMERIZATION REACTIONS- Chemical reactions that link two more small molecules to form larger molecules with repeating structural units • CONDENSATION REACTIONS polymerization reactions during which monomers are covalently linked, producing net removal of a water molecule for each covalent linkage • ***most polymerization reactions are condesation reactions CONDENSATION REACTIONS • One monomer loses a hydroxyl (-OH) and the other monomer loses a hydrogen (-H) • Process requires energy • Process requires biological catalysts or enzymes CONDENSATION REACTION QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. CONDENSATION AND HYDROLYSIS HYDROLYSIS • A REACTION THAT BREAKS COVALENT BONDS BETWEEN MONOMERS BY THE ADDITION OF WATER MOLECULES – A hydrogen from the water bonds to one monomer, and the hydroxyl bonds the adjacent monomer – EXAMPLE: digestive enzymes catalyze hydrolytic reactions which break apart large food molecules into monomers that can be absorbed in the bloodstream CARBOHYDRATES Fuel and Building Material • SUGARS-the smallest carbos, serve as fuel and carbon sources • CARBOHYDRATESorganic molecules made of sugars and their polymers • MONOSACCHARIDESthe building blocks of carbos-called simple sugars monosaccharides MONOSACCHARIDES • A simple sugar in which C,H,O occur in the ration of (CH20) – Are major nutrients for cells; glucose is the most common – Can be produced by photosynthetic organisms – Store energy in their chemical bonds which is harvested by cell respiration STRAIGHT AND RING GLUCOSE • RING FORM USED IN MAKING POLYMERSMORE STABLE CHARACTERTISTICS OF A SUGAR • An -OH group is attached to each carbon except one, which is double bonded to an oxygen (carbonyl) GLUCOSE MOLECULE-NOTICE DOUBLE BOND TO OXYGEN MORE CHARACTERISTICS OF MONOSACCHARIDES • The size of the carbon skeleton varies from three to seven carbons. • Spatial arrangement around asymmetric carbons may vary. For example, glucose and galactose are enantiomers • **the small difference between isomers affects molecular shape which gives each molecule distinctive biochemical properties • In aqueous solutions, many monosaccharides from rings. Chemical equilibrium favors ring structure DISACCHARIDES – A DOUBLE SUGAR THAT CONSISTS OF TWO MONOSACCHARIDES JOINED BY A GLYCOSIDIC LINKAGE – GLYCOSIDIC LINKAGE= covalent bond formed by a condensation reaction between two sugar monomers; for example maltose Glucose+ glucose = maltose Glucose + galactose = lactose Glucose + fructose = sucrose POLYSACCHARIDES • Macromolecules that are polymers of a few hundred or thousand monosaccharides – Are formed by linking monomers in enzyme-mediated condensation reactions – Have 2 important functions: – 1) energy storage (starch and glycogen); – 2) structural support (cellulose and chitin) POLYSACCHARIDES (GLYCOGEN) STORAGE POLYSACCHARIDES • Cells hydrolyze storage polysaccharides into sugars as needed. • Two most common storage polysaccharides are starch and glycogen ALPHA & BETA LINKAGES • ALPHA & BETA LINKAGES HAVE TO DO WITH WHERE THE HYDROXYL GROUP (-OH) IS ATTACHED TO THE #1 CARBON • ALPHA (a) = below the plane • BETA (b) = above the plane a & b LINKAGES STARCH • Glucose polymer that is a storage polysac. In plants • Helical glucose polymer with a 1-4 linkages • Stored as granules within plant organelles called plastids • Amylose, the simplest form, unbranched polymer • Amylopectin is branched polymer • Most animals have digestive enzymes to hydrolyze starch • Major sources in human diet are potatos and grains POLYSACCHARIDES GLYCOGEN • Glucose polymer that is a storage polysac. In animals • Large glucose polymer that is more highly branched than amylopectin • Stored in the muscle and liver of humans and other vertebrates GLYCOGEN STRUCTURAL POLYSACCHARIDES • INCLUDE CELLULOSE AND CHITIN • CELLULOSE- a major structural component of plant cell walls – Differs in starch in its glycosidic linkages – CELLULOSE FIBRILS FORMED BY HYDROGEN BONDING BETWEEN HYDROXYL GROUPS OF PARALLEL MOLECULES(PAGE 64) – Cannot be digested by most organisms, because they lack an enzyme that can hydrolyze the b 1-4 linkage; grazing animals are an exception to this STRUCTURAL POLYSACCHARIDES • CHITIN- a polymer of an amino sugar • Forms exoskeletons of arthropods • Found as a building material in the cell walls of some fungi • Monomer is an amino sugar, which is similar to b glucose with a nitrogen containing group replacing the hydroxyl on carbon 2. CHITIN IN EXOSKELTONS • WHICH OF THESE ANIMALS HAVE EXOSKELETONS? STARCH AND CELLULOSE • STARCH- glucose monomers are in a configuration (-OH group on carbon is below the ring’s plane) • CELLULOSE- glucose monomers are in b configuration (-OH group on carbon one is above the ring’s plane) LIPIDS • BUTTER: GOOD OR BAD??? LIPIDS: DIVERSE HYDROPHOBIC MOLECULES Lipids are a diverse group of organic compounds That are insoluble in water, but will dissolve in Nonpolar solvent (e.g. ether, chloroform,benzene), Important groups are fats, phospholipids, and Steroids. FATS STORE LARGE AMOUNTS OF ENERGY • FATS = Macromolecules constructed from – 1) GLYCEROL- a 3-carbon alcohol – 2) FATTY ACID- (carboxylic acid) • Made of a carboxyl group at one end and an attached hydrocarbon chain (tail) • Carboxyl functional group (head) has properties of an acid • Hydrocarbon chain has a long carbon skeleton usually with an even number of carbon atoms (16-18) • Nonpolar C-H bonds make the chain hydrophobic and not water soluble FORMATION OF FATS • DURING THE FORMATION OF A FAT, ENZYMECATALYZED CONDENSATION REACTIONS LINK GLYCEROL TO FATTY ACIDS BY AN ESTER LINKAGE, a bond between a hydroxyl group and a carboxyl group SOME CHARACTERISTICS OF FAT • Fats are insoluble in water. The long fatty acid chains are hydrophobic because of the many nonpolar C-H bonds • The source of variation among fat molecules is the fatty acid composition • Fatty acids in a fat may all be the same, or some (or all) may differ • Fatty acids may vary in length • Fatty acids may vary in the number and location of carbon-to-carbon double bonds SATURATED V. UNSATURATED FATS • SATURATED • No double bonds btw. carbons in fatty acid tail • Carbon skeleton of fatty acid is bonded to maximum number of hydrogens (saturated with hydrogens) • Usually solid at room temp • Most animal fats • UNSATURATED • One or more double bonds between carbons in fatty acid tail • Tail kinks at each C=C, so molecules do not pack closely enough to solidfy at room temp • Usually liquid at room temp • Most plant fats SATURATED AND UNSATURATED FAT MOLECULES WHICH IS SATURATED??? HINT: NO DOUBLE BONDS IN TAIL FATS SERVE USEFUL FUNCTIONS • ENERGY STORAGE- one gram of fat stored twice as much energy as carb or protein • CUSHIONS VITAL ORGANS IN MAMMALS • INSULATES AGAINST HEAT LOSS PHOSPHOLIPIDS • COMPOUNDS WITH MOLECULEAR BUILDING BLOCKS OF GLYCEROL, TWO FATTY ACIDS, A PHOSPHATE GROUP, AND USUALLY AND ADDITIONAL SMALL CHEMICAL GROUP ATTACHED TO THE PHOSPHATE PHOSPHOLIPID INFO. • Differ in fat in that the third carbon of glycerol is joined to a negatively charged phosphate • Can have small variable molecules attached to the phosphate • Show ambivalent behavior toward water. Hydrocarbon tails are hydrophobic and the polar head is hydrophilic • Cluster in water as their hydrophobic portions turn away from water • Are major constituents of cell membranes. PHOSPHOLIPID BILAYER • AT THE CELL SURFACE, PHOSPHOLIPIDS FROM A BILAYER HELD TOGETHER BY HYDROPHOBIC INTERACTIONS AMONG THE HYDROCARBON TAILS. STERIODS • LIPIDS which have four fused carbon rings with various functional groups • CHOLESTEROL IS AN IMPORTANT STERIOD – Is the precursor to many other steroids including vertebrate sex hormones and bile acids – Is the common component of animal cell membranes CHOLESTEROL PROTEINS • POLYPEPTIDE CHAINS- polymers of amino acids that are arranged in a specific sequence and are linked by peptide bonds • PROTEIN-Consists of one or more polypeptide chains folded and coiled into specific conformations – Are abundant, making up 50% or more of cellular dry weight – Vary extensively in structure – Are made up of only 20 different amino acids (mostly) – Have important and varied functions in the cell PROTEIN STRUCTURE QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. FUNCTIONS OF PROTEINS • • • • • • • STRUCTURAL SUPPORT STORAGE OF AMINO ACIDS TRANSPORT (E.G. HEMOGLOBIN) SIGNALING ( CHEMICAL MESSENGERS) MOVEMENT (CONTRACTILE PROTEINS) DEFENSE (ANTIBODIES) CATALYSIS OF REACTIONS (ENZYMES) POLYPEPTIDES • CHAINS OF AMINO ACIDS • CONSIST OF A CARBON, BONDED TO – – – – 1) HYDROGEN ATOM 2) CARBOXYL GROUP 3) AMINO GROUP 4) VARIABLE R GROUP (SIDE CHAIN) SPECIFIC TO EACH AMINO ACID PEPTIDE BOND • COVALENT BOND FORMED BY A CONDENSATION REACTION THAT LINKS CARBOXYL GROUP OF ONE AMINO ACID TO THE AMINO GROUP OF ANOTHER POLYPEPTIDE CHAINS RANGE IN LENGTH FROM A FEW AMINO ACIDS TO MORE THAN A THOUSAND PROTEIN SHAPES • A PROTEIN’S FUNCTION DEPENDS UPON ITS UNIQUE CONFORMATION • PROTEIN CONFORMATION-3-D SHAPE OF A PROTEIN • NATIVE CONFORMATIONFUNCTIONAL CONFORMATION OF A PROTEIN FOUND UNDER NORMAL BIOLOGICL CONDITIONS FOUR LEVELS OF PROTEIN STRUCTURE • PRIMARY STRUCTURE– A UNIQUE SEQUENCE OF AMINO ACIDS – DETERMINE BY GENS – SLIGHT CHANGE CAN AFFECT A PROTEIN’S CONFORMATION AND FUNCTION (E.G. SICKLE CELL HEMOGLOBIN) PRIMARY STRUCTURE PRIMARY STRUCTURE QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. SECONDARY STRUCTURE • REGULAR, REPEATED COILING AND FOLDING OF A PROTEIN’S POLYPEPTIDE BACKBONE • STABILIZED BY H+ BONDS BTW. PEPTIDE LINKAGES IN THE BACKBONE • THE MAJOR TYPES OF SECONDARY STRUCTURE ARE – ALPHA HELIX AND BETA PLEATED SHEET SECONDARY STRUCTURE • ALPHA HELIX BETA SHEETED • FOUND IN FIBROUS PROTEINS (KERATIN AND COLLAGEN) • H+ BONDS HELP WITH STABILIZATION SECONDARY STRUCTURE QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. TERTIARY STRUCTURE • THE 3-D SHAPE OF A PROTEIN • THE IRREGULAR CONTORTIONS OF A PROTEIN ARE DUE TO BONDING BTW. AND AMONG SIDE CHAINS (R GROUPS) AND TO INTERACTIONS BETWEEN R GROUPS AND THE AQUEOUS ENVIRONMENT • HYDROPHOBIC R GROUPS CLUMPS TOWARDS INSIDE AND HYDROPHILIC R GROUPS CLUMP TO THE OUTSIDE TERTIARY STRUCTURE • MANY ARE GLOBULAR PROTEINS TERTIARY STRUCTURE QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. QUARTERNARY STRUCTURE • RESULTS FROM THE INTERACTIONS BETWEEN AND AMON SEVERAL POLYPEPTIDE CHIANS – EX: COLLAGEN, A FIBROUS PROTEIN FOUND IN ANIMAL CONNECTIVE TISSUE, VERY STRONG DUE TO SHAPE QUARTERNARY STRUCTURE • MADE OF 2 OR MORE SEPARATE CHAINS, HELD TOGETHER BY H+ BONDS, INTERACTIONS AMONG R GROUPS, AND DISULFIDE BONDS QUARTERNARY STRUCTURE QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re. WHAT DETERMINES A PROTEIN’S SHAPE? • A PROTEIN’S 3-D SHAPE IS A CONSEQUENCE OF THE INTERACTIONS RESPONSIBLE FOR SECONDARY AND TERTIARY STRUCTURE • THIS CONFORMATION IS INFLUENCED BY PHYSICAL AND CHEMICAL ENVIRONMENTAL CONDITONS • IF A PROTEIN’S ENVIRONMENT IS ALTERED, IT MAY BECOME DENATURED AND LOSE ITS NATIVE CONFORMATION DENATURATION • PROTEINS CAN BE DENATURED BY: – TRANSFER TO AN ORGANIC SOLVENT – CHEMICAL AGENTS THAT DISRUPT H+ BONDS, IONIC BONDS AND DISULFIDE BRIDGES – EXCESSIVE HEAT – ***SOME DENATURED PROTEINS WILL RETURN TO THEIR NATIVE CONFORMATION WHEN CONDITIONS RETURN TO NORMAL NUCLEIC ACIDS: INFORMATIONAL POLYMERS • NUCLEIC ACIDS STORE AND TRANSMIT HEREDITARY INFORMATION • PROTEIN CONFORMATION IS DETERMINED BY PRIMARY STRUCTURE. PRIMARY STRUCTURE IN TURN, IS DETERMINED BY GENES; HEREDITARY UNITS THAT CONSIST OF DNA, A TYPE OF NUCLEIC ACID. • THERE ARE 2 TYPES OF NUCLEIC ACIDS 2 TYPES OF NUCLEIC ACIDS • DNA – CONTAINS CODED INFO THAT PROGRAMS ALL CELL ACTIVITY – CONTAINS DIRECTIONS FOR ITS OWN REPLICATION – IS COPIED AND PASSED FROM ONE GENERATION OF CELLS TO ANOTHER – IS FOUND IN THE NUCLEUS – MAKES UP GENES THAT CONTAIN INSTRUCTIONS FOR PROTEIN SYNTHESIS • RNA – FUNCTIONS IN THE ACTUAL SYNTHESIS OF PROTEINS CODED FOR BY DNA – SITES OF PROTEIN SYNTHESIS ARE ON RIBOSOMES IN THE CYTOPLASM – MESSENGER RNA (mRNA) CARRIES ENCODED GENETIC MESSAGE FROM THE NUCLEUS TO THE CYTOPLASM – THE FLOW OF GENETIC INFO GOES FROM: – DNA>>>RNA>>>PROTEINS DNA TO PROTEINS NUCEIC ACID STRAND: A POLYMER OF NUCLEOTIDES • NUCLEIC ACID- polymer of nucleotides linked together by condensation reactions • NUCLEOTIDE- building block molecule of nucleic acid; made of – 1) five carbon sugar covalently bonded to – 2) phosphate group – 3) a nitrogenous base THE STRUCTURE OF NUCLEOTIDES NUCLEOTIDE WITH ADENINE (BASE) NITROGENOUS BASES • THERE ARE 2 FAMILIES OF NITROGENOUS BASES – PYRIMIDINES: A SIX-MEMBERED RING MADE OF CARBON AND NITROGEN • CYTOSINE(C) • THYMINE (T);FOUND ONLY IN DNA • URACIL (U); FOUND ONLY IN RNA -PURINES: A FIVE-MEMBERED FING FUSED TO A SIXMEMBERED RING ADENINE(A) GUANINE(G) ATP- chemical energy nucleotide • Adenine, 5-carbon sugar, 3 phosphate groups DNA • RESULTS FROM JOINING NUCLEOTIDES TOGETHER BY COVALENT BONDS CALLED PHOSPHODIESTER LINKAGES. THE BOND IS FORMED BETWEEN THE PHOSPHATE OF ONE NUCLEOTIDE AND THE SUGAR OF THE NEXT