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This chapter explores the properties and structures of organic compounds, focusing on carbon atoms, isomers, functional groups, polymers, carbohydrates, lipids, and proteins.
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The Chemistry of Life:Organic Compounds Chapter 3
Learning Objective 1 • What properties make carbon the central component of organic compounds?
Carbon Atoms • form four covalent bonds • single, double, or triple • straight or branched chains • rings • bond with many different elements
Organic Molecules • Chains
Organic Molecules • Double bonds
Organic Molecules • Branched chains
Organic Molecules • Rings
KEY CONCEPTS • Carbon atoms join with one another or other atoms to form large molecules with a wide variety of shapes
Learning Objective 2 • What is an isomer? • What are the 3 principal isomer types?
Isomers • Structural isomers • different covalent arrangements
Isomers • Geometric isomers (cis–trans isomers) • different spatial arrangements
Isomers • Enantiomers • mirror images
Learning Objective 3 • What are the major functional groups present in organic compounds, and their properties?
Hydrocarbons • Organic compounds • carbon and hydrogen only • nonpolar • hydrophobic • Methyl group
Polar and Ionic Functional Groups • Partial charges on atoms • at opposite ends of a bond • interact with one another • hydrophilic • Hydroxyl and carbonyl groups
Acidic and Basic Groups • Acidic • release hydrogen ions • become negatively charged • carboxyl and phosphategroups • Basic • accepts a hydrogen ion • become positively charged • amino group
Functional Groups • Polar (hydroxyl) • Acidic (carboxyl) • Basic (amino)
KEY CONCEPTS • Hydrocarbons • nonpolar and hydrophobic • Properties depend on functional groups: • hydroxyl and carbonyl groups (polar) • carboxyl and phosphate groups (acidic) • amino groups (basic)
Learning Objective 4 • What is the relationship between polymers and macromolecules?
Polymers and Macromolecules • Polymers • long chains of monomers • linked through condensation reactions • Macromolecules • large polymers • polysaccharides, proteins, and DNA • broken down by hydrolysis reactions
Condensation Enzyme A HO OH HO OH HO O OH H2O + Hydrolysis Monomer Monomer Dimer Enzyme B Fig. 3-5, p. 50
Learning Objective 5 • Distinguish among monosaccharides, disaccharides, and polysaccharides • What is the difference between storage polysaccharides and structural polysaccharides?
Carbohydrates • Ratio • 1carbon: 2 hydrogen: 1 oxygen • Monosaccharide • simple sugar • glucose, fructose, ribose • Disaccharide • 2 monosaccharides • joined by glycosidic linkage • maltose, sucrose
Glyceraldehyde (C3H6O3) (an aldehyde) Dihydroxyacetone (C3H6O3) (a ketone) (a) Triose sugars (3-carbon sugars) Fig. 3-6, p. 51
Ribose (C5H10O5) (the sugar component of RNA) Deoxyribose (C5H10O4) (the sugar component of DNA) (b) Pentose sugars (5-carbon sugars) Fig. 3-6, p. 51
Glucose (C6H12O6) (an aldehyde) Fructose (C6H12O6) (a ketone) Galactose (C6H12O6) (an aldehyde) (c) Hexose sugars (6-carbon sugars) Fig. 3-6, p. 51
Polysaccharides • Long chains • repeating units of simple sugar • Storage polysaccharides • starch in plants • glycogen in animals • Structural polysaccharide • cellulose, cell walls of plants
Polysaccharides • Starch
KEY CONCEPTS • Carbohydrates are composed of sugar subunits (monosaccharides), which can be joined to form disaccharides, storage polysaccharides, and structural polysaccharides
Learning Objective 6 • What are the characteristics, composition, and biological functions of fats, phospholipids, and steroids?
Lipids • Mainly hydrocarbon-containing regions • few oxygens (polar or ionic groups) • Greasy or oily consistency • relatively insoluble in water
Fats • Triacylglycerol • main storage fat • glycerol + 3 fatty acids • Monoacylglycerols & diacylglycerols • 1 or 2 fatty acids • saturated or unsaturatedfatty acid • hydrogens
Ester linkage A triacylglycerol Fig. 3-12b, p. 56
Phospholipids • Structure • glycerol • 2 fatty acids • phosphate group • Function • cell membrane component
Phosphate group Glycerol Fatty acids Choline Water Hydrophilic head Hydrophobic tail Fig. 3-13, p. 58
Steroids • Carbon atoms arranged in 4 rings • cholesterol, bile salts, some hormones
Indicates double bond Cholesterol (a) Cholesterol is an essential component of animal cell membranes. Fig. 3-15a, p. 59
KEY CONCEPTS • Lipids store energy (triacylglycerol) and are the main structural components of cell membranes (phospholipids)
Learning Objective 7 • What are the structures and functions of proteins?
Proteins • Polypeptides • long, linear polymers • 20 amino acids (monomers) • joined by peptide bonds • Many functions • enzymes • structural components • cell regulators
Carboxyl group Amino group Peptide bond R group R group Glycine Alanine Glycylalanine (a dipeptide) Fig. 3-18, p. 63
Learning Objective 8 • What features are shared by all amino acids? • How are amino acids grouped into classes based on their side chains?
Amino Acids • Amino group and carboxyl group • Side chains • determine chemical properties • nonpolar, polar, acidic, or basic • Dipolar ions at cell pH • important biological buffers