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Chapter 5 The Structure and Function of Large Biological Molecules Focus on: • Elements in each large biological molecule. • How these molecules are linked and unlinked. • Examples and functions of each type of molecule. Macromolecules • Large molecules formed by joining many subunits together. • Also known as “polymers”. Monomer • A building block of a polymer. Condensation Synthesis or Dehydration Synthesis • The chemical reaction that joins monomers into polymers. • Covalent bonds are formed by the removal of a water molecule between the monomers. Hydrolysis • Reverse of condensation synthesis. • Hydro- water • Lysis - to split • Breaks polymers into monomers by adding water. Four Main Types of Macromolecules or Large Biological Molecules • • • • Carbohydrates Lipids Protein Nucleic acids For each Macromolecule know the following: • • • • Elements it contains Monomer units and structures Examples Uses or roles Carbohydrates • Used for fuel, building materials, and receptors. • Made of C,H,O • General formula is CH2O • C:O ratio is 1:1 Types Of Carbohydrates • • • • Monosaccharides Disaccharides Oligosaccharides Polysaccharides Monosaccharides • • • • • Mono - single Saccharide - sugar Simple sugars. 3 to 7 carbons. Can be in linear or ring forms. Monosaccharides • Can be “Aldoses” or “Ketoses” depending on the location of the carbonyl group. Examples • • • • Glucose Galactose Ribose Fructose - OSE • Word ending common for many carbohydrates. Disaccharides • Di - two • Sugar formed by joining two monosaccharides through a “glycosidic linkage”. Examples • Maltose = glucose + glucose • Lactose = glucose + galactose • Sucrose = glucose + fructose Oligosaccharides • Oligo – a few • 2 - 10 joined simple sugars. • Used in cell membranes. Polysaccharides • • • • Poly - many Many joined simple sugars. Used for storage or structure. Examples: • Starch • Cellulose • Glycogen a glucose and b glucose Starch • Made of 1-4 linkages of a glucose. • Linkage makes the molecule form a helix. • Fuel storage in plants. a glucose Cellulose • Made of 1-4 linkages of b glucose. • Linkage makes the molecule form a straight line. • Used for structure in plant cell walls. b glucose Comment • Most organisms can digest starch (1- 4 a linkage), but very few can digest cellulose (1- 4 b linkage). • Another example of the link between structure and function. Glycogen • “Animal starch” • Similar to starch, but has more 1-6 linkages or branches. • Found in the liver and muscle cells. Starch Glycogen Lipids • Diverse hydrophobic molecules • Made of C,H,O • No general formula • C:O ratio is very high in C • Not strictly speaking a macromolecule like the others Fats and Oils • Fats - solid at room temperature. • Oils - liquid at room temperature. Fats and Oils • Made of two kinds of smaller molecules. • Fatty Acids • Glycerol Fatty Acids • A long carbon chain (12-18 C) with a -COOH (acid) on one end and a -CH3 (fat) at the other. Acid Fat Neutral Fats or Triacylglycerols • Three fatty acids joined to one glycerol. • Joined by an “ester linkage” between the -COOH of the fatty acid and the -OH of the alcohol. Saturated Fats Unsaturated Fats • Saturated - no double bonds. • Unsaturated - one or more C=C bonds. Can accept more Hydrogens. • Double bonds cause “kinks” in the molecule’s shape. Question • Why do fats usually contain saturated fatty acids and oils usually contain unsaturated fatty acids? • The double bond pushes the molecules apart, lowering the density, which lowers the melting point. Fats • Differ in which fatty acids are used. • Used for energy storage, cushions for organs, insulation. Question ? • Which has more energy, a kg of fat or a kg of starch? • Fat - there are more C-H bonds which provide more energy per mass. Phospholipids • Similar to fats, but have only two fatty acids. • The third -OH of glycerol is joined to a phosphate containing molecule. Result • Phospholipids have a hydrophobic tail, but a hydrophilic head. • Self-assembles into micells or bilayers, an important part of cell membranes. Steroids • Lipids with four fused rings. • Differ in the functional groups attached to the rings. • Examples: • cholesterol • sex hormones Proteins • The molecular tools of the cell. • Made of C,H,O,N, and sometimes S. • No general formula. Uses Of Proteins • • • • • • • Structure Enzymes Antibodies Transport Movement Receptors Hormones Proteins • Polypeptide chains of Amino Acids linked by “peptide bonds”. Amino Acids • All have a Carbon with four attachments: • -COOH (acid) • -NH2 (amine) • -H • -R (some other side group) R groups • 20 different kinds: • Nonpolar - 9 AA • Polar - 6 AA • Electrically Charged • Acidic - 2 AA • Basic - 3 AA Amino Acids Amino Acids R groups • Contain the S when present in a protein. • Cysteine or Cys • Methionine or Met • The properties of the R groups determine the properties of the protein. Polypeptide Chains • Formed by dehydration synthesis between the carboxyl group of one AA and the amino group of the second AA. • Produce an backbone of: (N-C-C)X Levels Of Protein Structure • Organizing the polypeptide into its 3-D functional shape. • • • • Primary Secondary Tertiary Quaternary Primary • Sequence of amino acids in the polypeptide chain. • Many different sequences are possible with 20 AAs. Secondary • 3-D structure formed by hydrogen bonding between parts of the peptide backbone. • Two main secondary structures: a helix β pleated sheets Tertiary • Bonding between the R groups. • Examples: • • • • hydrophobic interactions ionic bonding Disulfide bridges (covalent bond) Can also include H bonds Quaternary • When two or more polypeptides unite to form a functional protein. • Example: hemoglobin Is Protein Structure Important? Denaturing Of A Protein • Events that cause a protein to lose structure (and function). • Example: • pH shifts • high salt concentrations • heat Chaperone Proteins • Large protein complexes that help fold other proteins into their correct shape. • Often used when cells are stressed to keep proteins intact and functioning. • First found in “heat stress”. Comment • Many other amino acids are possible (change the R group). • Whole new group of proteins with new properties can be made. • Genetic engineering can use bacteria to make these new proteins. Nucleic Acids • • • • Informational polymers Made of C,H,O,N and P No general formula Examples: DNA and RNA Nucleic Acids • Polymers of nucleotides • Nucleotides have three parts: • nitrogenous base • pentose sugar • phosphate Nitrogenous Bases • Rings of C and N • The N atoms tend to take up H+ (act as a base). • Two types: • Pyrimidines (single ring) • Purines (double rings) Pentose Sugar • • • • 5-C sugar Ribose - RNA Deoxyribose – DNA RNA and DNA differ in a –OH group on the 2nd carbon. Nucleosides and Nucleotides • Nucleoside = base + sugar • Nucleotide = has the trio of base + sugar + Pi DNA • Deoxyribonucleic Acid. • Makes up genes. • Genetic information for life. RNA • Ribonucleic Acid. • Structure and protein synthesis. • Genetic information for a few viruses only. • Control mechanisms for genes (major future topic). DNA and RNA • More will be said about DNA and RNA in future lessons. Chapter Summary • Role of hydrolysis and dehydration synthesis • For each macromolecule, know the following: • • • • Elements and monomers Structures Functions Examples