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Chapter 3

Chapter 3







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    Chapter 3 Chapter 3 Presentation Transcript

    • Chapter 3Proteins, Carbohydrates, and Lipids
    • MacromoleculesPolymers with molecular weights >1,000Made up of smaller molecules calledmonomersFour Main Groups: Proteins (Amino Acids) Carbohydrates (Simple Sugars) Lipids (Fatty Acids) Nucleic Acids (Nucleotides - Chapter 4)
    • Functional GroupsGroups of atoms withspecific chemicalproperties and consistentbehavior
    • IsomersMolecules with the same chemical formula, butatoms are arranged differentlyStructural Isomers: differ in how their atomsare joined together
    • Optical IsomersOccur when a carbonatom has fourdifferent atoms orgroups of atomsattached to it.Optical isomers resultfrom asymmetricalcarbons.
    • Macromolecules Found in Living Tissues
    • Functions of Macromolecules• Energy Storage • Maintenance and• Structural Support Homeostasis• Catalysts • Movement• Transport • Growth• Protection and • Development Defense • Heredity• Regulation of • Information Storage Metabolic Activities
    • Condensation ReactionsPolymers are formed incondensation reactions.Monomers are joined bycovalent bonds.A water is removed; sothey are also calleddehydration reactions.
    • Hydrolysis ReactionsPolymers are brokendown into monomersin hydrolysisreactions.
    • Protein StructureProteins are polymers of 20 different amino acids.Polypeptide chain: single, unbranched chain of aminoacids.The chains are folded into specific three dimensionalshapes defined by the sequence of the amino acids.Proteins can consist of more than one type ofpolypeptide chain.
    • Functions of Proteinsenzymes—catalytic proteinsdefensive proteins (e.g., antibodies)hormonal and regulatory proteins—control physiologicalprocessesreceptor proteins—receive and respond to molecular signalsStorage proteins store amino acids.Structural proteins provide physical stability and movement.Transport proteins carry substances within the organism (e.g.,hemoglobin).Genetic regulatory proteins regulate when, how, and to whatextent a gene is expressed.
    • Building Blocks of Proteins: Amino Acidsα-carbon is “asymmetric”4 Main Groups• Amino Group• Carboxyl Group• Hydrogen• Side Chain (R) –Specific to each type of amino acid D-amino acids (dextro, “right”) L-amino acids (levo, “left”)•Optical Isomers (this form is found in organisms)
    • Types of Amino Acid Side Chains (R)These hydrophylic amino acids attractions of opposite charges.
    • Types of Amino Acid Side Chains (R)Hydrophylic amino acids with polar butuncharged side chains form hydrogen bonds.
    • Types of Amino Acid Side Chains (R)Hydrophobic amino acids
    • Types of Amino Acid Side Chains (R)Cysteine: Can form disulfide bridgesGlycine: Smallest a.a. (Unique why?)Proline: Causes “kinks” in protein structure
    • Peptide BondsN-terminus: start of a polypeptide chainC-terminus: end of a polypeptide chain
    • Levels of Protein Structure: Primary StructureMade up of a single chain of amino acidsbound together (polypeptide)The number of different proteins that canbe made from 20 amino acids isenormous!
    • Levels of Protein Structure: Secondary Structureα helix: right-handed coil resulting from hydrogen bonding between N—H groups on one amino acid and C=O groups on another.β pleated sheet: two or more polypeptide chains are aligned; hydrogen bonds from between the chains. Bonds do NOT form between side chains!
    • Levels of Protein Structure: Tertiary Structure• Bending and folding results in a macromolecule with specific three- dimensional shape.• Bonds form between side chains
    • Levels of Protein Structure: Quaternary StructureResults from theinteraction of subunitsby hydrophobicinteractions, van derWaals forces, ionicbonds, and hydrogenbonds.Each subunit has itsown unique tertiarystructure.
    • Environmental Conditions affect Protein FoldingConditions that affect secondary and tertiary structure:• High temperature• pH changes• High concentrations of polar molecules• Nonpolar substances
    • Denaturation
    • ChaperonesHelp some proteins fold correctly
    • CarbohydratesCarbohydrates have the general formulaCn(H2O)nSource of stored energyTransport stored energy
    • Types of CarbohydratesMonosaccharides: simple sugarsDisaccharides: two simple sugars linked by covalent bondsOligosaccharides: three to 20 monosaccharidesPolysaccharides: hundreds or thousands of monosaccharides—starch, glycogen, cellulose
    • MonosaccharidesSimple SugarsHexoses: sixPentoses: five carbonsGlyceraldehyde: three carbons
    • Monosaccharides: GlucoseAll cells use glucose (monosaccharide) as an energy source.Exists as a straight chain or ring form. Ring is more common—it is more stable.
    • Glycosidic LinkagesMonosaccharides bind together in condensation reactions to form glycosidic linkages.Glycosidic linkages can be α or β.
    • OligosaccharidesOften covalently bonded to proteins and lipids on cell surfaces and act as recognition signals.Human blood groups get specificity from oligosaccharide chains.
    • PolysaccharidesGiant polymers of monosaccharides. Starch: storage of glucose in plants Glycogen: storage of glucose in animals Cellulose: very stable, good for structural components
    • Carbohydrates can be modified by the addition of functional groups
    • LipidsNonpolar hydrocarbonsNot polymers in the strict sense, because they are not covalently bonded.FUNCTION:1) Fats and oils store energy2) Phospholipids—structural role in cell membranes3) Carotenoids and chlorophylls—capture light energy in plants4) Steroids and modified fatty acids—hormones and vitamins5) Animal fat—thermal insulation6) Lipid coating around nerves provides electrical insulation7) Oil and wax on skin, fur, and feathers repels water
    • TriglyceridesSimple fats and oilsGlycerol: 3 —OH groups (an alcohol)Fatty acid: nonpolar hydrocarbon with a polarcarboxyl groupCarboxyls bond with hydroxyls of glycerol in anester linkage. (condensation reaction)
    • Ester Linkage
    • Types of Fatty AcidsSaturated fatty acids: no double bonds between carbons—it is saturated with H atoms.Unsaturated fatty acids: some double bonds in carbon chain. monounsaturated: one double bond polyunsaturated: more than one
    • Types of Fatty AcidsSaturated Unsaturated
    • PhospholipidsFatty acids bound toglycerol; a phosphategroup replaces one fattyacid.Hydrophilic “head”Hydrophobic “Tails”Amphipathic:Have opposing chemicalproperties
    • Phospholipid Bilayer• In water, phospholipids line up with the hydrophobic “tails” together and the phosphate “heads” facing outward, to form a bilayer.
    • Other Fats