Chapter 5~ The Structure & Function of Macromolecules

Carbohydrates, I

Monosaccharides

C(H 2 O)n formula;

multiple hydroxyl (-OH) groups and 1 carbonyl (C=O) group:

aldehyde (aldoses) sugar

ketone sugar

cellular respiration;

raw material for amino acids and fatty acids

Carbohydrates, II

Disaccharides

glycosidic linkage (covalent bond) between 2 monosaccharides;

covalent bond by dehydration reaction

Sucrose (table sugar) -- most common disaccharide

Disaccharides

      two monosaccharides attached by a condensation reaction.

     examples: sucrose, lactose, maltose

Carbohydrates, III

Polysaccharides

Storage:

• Starch~ glucose monomers

• Plants: plastids

• Animals: glycogen

Polysaccharides

Structural:

• Cellulose~ most abundant organic compound;

• Chitin~ exoskeletons; cell walls of fungi; surgical thread

Lipids

No polymers; glycerol and fatty acid

Fats, phospholipids, steroids

Hydrophobic; H bonds in water exclude fats

Carboxyl group = fatty acid

Non-polar C-H bonds in fatty acid ‘tails’

Ester linkage: 3 fatty acids to 1 glycerol (dehydration formation)

Triacyglycerol (triglyceride)

Saturated vs. unsaturated fats; single vs. double bonds

Lipids, II

Phospholipids

• 2 fatty acids instead of 3 (phosphate group)

• ‘Tails’ hydrophobic; ‘heads’ hydrophilic

• Micelle (phospholipid droplet in water)

• Bilayer (double layer); cell membranes

Steroids

• Lipids with 4 fused carbon rings

• Ex: cholesterol: cell membranes; precursor for other steroids (sex hormones); atherosclerosis

• Proteins

Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known

Monomer: amino acids (there are 20) ~ carboxyl (-COOH) group, amino group (NH 2 ), H atom, variable group (R)….

Variable group characteristics: CAN BE: polar (hydrophilic), nonpolar (hydrophobic), acid or base, ionic

Three-dimensional shape (conformation)

Polypeptides (dehydration reaction): peptide bonds~ covalent bond; carboxyl group to amino group (polar)

Protein Structure

Primary Structure

• Conformation: Linear structure

• Molecular Biology: each type of protein has a unique primary structure of amino acids

• Ex: lysozyme

• Amino acid substitution: hemoglobin; sickle-cell anemia

Secondary Structure

• Conformation: coils & folds (hydrogen bonds)

• Alpha Helix: coiling; keratin

• Pleated Sheet: parallel; silk

Tertiary Structure

Conformation:

• irregular contortions from R group bonding

• hydrophobic

• disulfide bridges

• hydrogen bonds

• ionic bonds

Tertiary Protein Structure

Quaternary Structure

Conformation:

• 2 or more polypeptide chains aggregated into 1 macromolecule

• collagen (connective tissue)

• hemoglobin

Nucleic Acids, I

• Deoxyribonucleic acid (DNA)

• Ribonucleic acid (RNA)

• DNA->RNA->protein

• Polymers of nucleotides (polynucleotide): nitrogenous base pentose sugar phosphate group

• Nitrogenous bases: pyrimidines~ cytosine, thymine, uracil purines~adenine, guanine

Nucleic Acids, II

Pentoses:

ribose (RNA), deoxyribose (DNA), nucleoside (base + sugar)

Polynucleotide: phosphodiester linkages (covalent); phosphate + sugar

Nucleic Acids, III

• Inheritance based on DNA replication

• Double helix (Watson & Crick - 1953)

• H bonds~ between paired bases

• van der Waals~ between stacked bases

• A to T; C to G pairing

• Complementary