The Structure and Function of Macromolecules

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Chapter 5

• The Structure and Function of Macromolecules

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Macromolecules

• Four Classes
• 1. Carbohydrates
• 2. Lipids
• 3. Proteins
• 4. Nucleic acids

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Polymer

• Chain of linked monomers
• polymer monomer
• 1. Carbohydrates ------ sugar
• 2. Proteins --------------- amino acids
• 3. Nucleic acids -------- nucleotides

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Composite molecule

• Lipids ---------glycerol fatty acid(s)

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Bonds

• macromolecule bond type
• 1. Carbohydrates - glycosidic linkage
• 2. Lipids ------------- ester linkage
• 3. Proteins ---------- peptide bond
• 4. Nucleic acids --- phosphodiester
  
  bond

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Chemical Reactions

• Condensation synthesis (Dehydration ) - remove a
  water molecule, polymerize
• Hydrolysis - add a water molecule, depolymerize

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Metabolism

• Anabolism - synthesize molecules
• polymerization
• dehydration
• Catabolism - breakdown molecules
• depolymerization
• hydrolysis

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Carbohydrates

• CHO
• function energy storage
• three groups
• -monosaccharides
• -disaccharides
• -polysaccharides

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1. Monosaccharides

• (CH2O) n 3 to 7
• n3 triose
• n4 tetrose
• n5 pentose
• n6 hexose
• n7 heptose
• some exceptions to empirical formula

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Monosaccharides cont.

• Examples of hexoses C6H12O6
• glucose
• fructose
• galactose
• structural isomers

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2. Disaccharides

• Ex
• monosaccharides disaccharide
• glucose glucose maltose
• glucose galactose lactose
• glucose fructose sucrose
• formed through dehydration

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3. Polysaccharide

• Covalently bonded glucose units
• Glycosidic linkage - covalent bond between
  glucose units

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3. Polysaccharides cont.

• Examples
• a. Starches amylose - unbranched
• amylopectin-branched
• b. glycogen - highly branched
• c. cellulose - unbranched,
• alternating OH groups
• d. chitin - glucose N

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Lipids

• CHO
• Function long-term energy storage
• fats, phospholipids, steroids, pigments
• water-insoluble, nonpolar

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1. Fats

• Glycerol fatty acid (s)
• fatty acids (f.a.)
• 1 f.a. monoglyceride
• 2 f.a. diglyceride
• 3 f.a. triglyceride, (triacylglycerol)
• glycerol - 3C alcohol

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Fats cont.

• ester linkage - bond
  between carboxyl (f.a.) and hydroxyl
  (glycerol)
• fatty acids
• saturated
• unsaturated

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Fatty acids

• Saturated
• -maximum number of H
• -no double bonds
• -usually solid
• -ex. animal fats (butter, lard)

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Fatty acids cont.

• Unsaturated
• - 1 double bond (mono-)
• - more than 1 double bond (poly-)
• -usually liquid
• -ex. Oils (nut and seed)

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Fatty acids cont.

• peanut oil peanut butter
• hydrogenation unsaturated
  saturated
• fat yields 2X energy/gram than carbo

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2. Other Lipids

• Phospholipids
• phosphate 2 f.a. glycerol
• Steroids
• cholesterol
• Pigments
• chlorophylls - xanthophylls
• carotenes - anthocyanins

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Proteins

• CHON
• Function diverse
• structures, contraction, storage, defense,
  transport, messengers, enzymes
• monomer amino acid

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Proteins cont.

• amino acids (20) most contain
• -central C
• -amino group
• -carboxyl group
• -H atom
• -functional group (R)

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Proteins cont.

• -dipeptide------------- 2 a.a.
• -tripeptide------------- 3 a.a.
• -polypeptide---------- 4 or more a.a
• Peptide bond is found between 2 amino acids
  (a.a.)
• dehydration reaction
• protein usu. several polypeptides

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Levels of Protein Structure

• The following determine the shape of the protein
  (polypeptide)
• primary
• secondary
• tertiary
• quaternary

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Primary Structure of a Protein

• a.a. sequence

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Secondary Structure of a Protein

• Bending and H-bonding to form alpha helices
  (coils) and beta sheets (strands)

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Tertiary Structure of a Protein

• overall conformation of the polypeptide
• hydrophobic interactions
• ionic bonds
• disulfide bridges

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Quaternary Structure of a Protein

• Relationship between 2 or more polypeptides that
  make up the protein

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Protein Conformation

• Altering any level will change the final
  conformation
• denaturation - unravel the protein
• caused by several different factors

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Nucleic Acids

• CHONP
• Function store information
• monomer - nucleotide
• ex.
• DNA
• RNA

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Nucleotide

• Phosphate sugar N-base
• phosphodiester bond
• between phosphate and sugar

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DNA

• Deoxyribonucleic acid
• dsDNA
• nucleus
• nucleotide
• phosphate sugar N-base
• phosphate deoxyribose A,G,C or (pentose)
  T

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RNA

• Ribonucleic acid
• ssRNA
• cytoplasm
• nucleotide
• phosphate sugar N-base
• phosphate ribose A,G,C or
  (pentose) U

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N-bases

• Purines
• two-ringed structures
• A,G
• Pyrimidines
• single-ringed structures
• C,T,U
• N-base pairing purine---pyrimidine

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N-base pairing

• DNA-----DNA
• A ----------T
• G --------- C
• T ---------- A
• C --------- G

• RNA------DNA
• A -----------T
• G ---------- C
• U ---------- A
• C ---------- G

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Chapter 5

• The End