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Biochemistry is the study of chemical composition and reactions of living matter • All chemicals either organic or inorganic– Inorganic compounds • Water, salts, and many acids and bases • Do not contain carbon– Organic compounds • Carbohydrates, fats, proteins, and nucleic acids • Contain carbon, are usually large, and are covalently bonded • Both equally essential for life © 2016 Pearson Education, Ltd. 2.6 Inorganic Compounds Water • Most abundant inorganic compound– Accounts for 60%–80% of the volume of living cells • Most important inorganic compound because of its properties– High heat capacity– High heat of vaporization– Polar solvent properties– Reactivity– Cushioning © 2016 Pearson Education, Ltd. Water • High heat capacity– Ability to absorb and release heat with little temperature change– Prevents sudden changes in temperature • High heat of vaporization– Evaporation requires large amounts of heat– Useful cooling mechanism © 2016 Pearson Education, Ltd. Water (cont.) • Polar solvent properties– Dissolves and dissociates ionic substances– Forms hydration (water) layers around large charged molecules • Example: proteins– Body’s major transport medium © 2016 Pearson Education, Ltd. Water (cont.) • Reactivity– Necessary part of hydrolysis and dehydration synthesis reactions • Cushioning– Protects certain organs from physical trauma • Example: cerebrospinal fluid cushions nervous system organs © 2016 Pearson Education, Ltd. Salts • Salts are ionic compounds that dissociate into separate ions in water– Separate into cations (positively charged molecules) and anions (negatively charged) • Not including H+ and OH– ions– All ions are called electrolytesbecause they can conduct electrical currents in solution– Ions play specialized roles in body functions • Example: sodium, potassium, calcium, and iron– Common salts in body • NaCl, CaCO3, KCl, calcium phosphates © 2016 Pearson Education, Ltd. Clinical – Homeostatic Imbalance 2.1 • Ionic balance is vital for homeostasis • Kidneys play a big role in maintaining proper balance of electrolytes • If electrolyte balance is disrupted, virtually all organ systems cease to function © 2016 Pearson Education, Ltd. Acids and Bases • Acids and basesare both electrolytes– Ionize and dissociate in water • Acids– Are proton donors: they release hydrogen ions (H+), bare protons (have no electrons) in solution • Example: HCl →H+ + Cl–– Important acids • HCl (hydrochloric acid), HC2H3O2 (acetic acid, abbreviated HAc), and H2CO3 (carbonic acid) © 2016 Pearson Education, Ltd. Acids and Bases (cont.) • Bases– Are proton acceptors: they pick up H+ ions in solution • Example: NaOH → Na+ + OH–– When a base dissolves in solution, it releases a hydroxyl ion (OH–)– Important bases • Bicarbonate ion (HCO3–) and ammonia (NH3) © 2016 Pearson Education, Ltd. Acids and Bases (cont.) • pH: Acid-base concentration– pHscaleis measurement of concentration of hydrogen ions [H+] in a solution– The more hydrogen ions in a solution, the more acidic that solution is– pH is negative logarithm of [H+] in moles per liter that ranges from 0–14– pH scale is logarithmic, so each pH unit represents a 10-fold difference • Example: a pH 5 solution is 10 times more acidic than a pH 6 solution © 2016 Pearson Education, Ltd. Acids and Bases (cont.) • pH: Acid-base concentration (cont.)– Acidic solutions have high [H+] but low pH • Acidic pH range is 0–6.99– Neutral solutions have equal numbers of H+ and OH– ions • All neutral solutions are pH 7 • Pure water is pH neutral– pH of pure water = pH 7: [H+] = 10–7 m– Alkaline (basic) solutions have low [H+] but high pH • Alkaline pH range is 7.01–14 © 2016 Pearson Education, Ltd. Figure 2.13 The pH scale and pH values of representative substances. Concentration (moles/liter) [OH−] [H+] pH 100 10−14 10−1 10−2 10−3 10−4 10−5 10−6 10−7 10−8 10−9 10−13 10−12 10−11 10−10 10−9 10−8 10−7 10−6 14 13 12 11 10 9 8 Examples 1MSodium hydroxide (pH=14) Increasingly basic Oven cleaner, lye (pH=13.5) Household ammonia (pH=10.5–11.5) Household bleach (pH=9.5) Egg white (pH=8) 7 6 10−5 10−10 10−11 10−12 10−13 10−14 10−4 10−3 10−2 10−1 100 5 4 3 2 1 0 Neutral Increasingly acidic Blood (pH=7.4) Milk (pH=6.3–6.6) Black coffee (pH=5) Wine (pH=2.5–3.5) Lemon juice; gastric juice (pH=2) 1MHydrochloric acid(pH=0) © 2016 Pearson Education, Ltd. Acids and Bases (cont.) • Neutralization– Neutralization reaction: acids and bases are mixed together • Displacement reactions occur, forming water and a salt NaOH+ HCl → NaCl+ H2O © 2016 Pearson Education, Ltd. Acids and Bases (cont.) • Buffers– Acidity involves only free H+ in solution, not H+ bound to anions– Buffers resist abrupt and large swings in pH • Can release hydrogen ions if pH rises • Can bind hydrogen ions if pH falls– Convert strong acids or bases (completely dissociated) into weak ones (slightly dissociated) • Carbonic acid–bicarbonate system (important buffer system of blood): © 2016 Pearson Education, Ltd. 2.7 Organic Compounds: Synthesis and Hydrolysis • Organic molecules contain carbon– Exceptions: CO2 and CO, which are inorganic • Carbon is electroneutral– Shares electrons; never gains or loses them– Forms four covalent bonds with other elements– Carbon is unique to living systems • Major organic compounds: carbohydrates, lipids, proteins, and nucleic acids © 2016 Pearson Education, Ltd. 2.7 Organic Compounds: Synthesis and Hydrolysis • Many are polymers– Chains of similar units called monomers (building blocks) • Synthesized by dehydration synthesis • Broken down by hydrolysis reactions © 2016 Pearson Education, Ltd. Figure 2.14 Dehydration synthesis and hydrolysis. Dehydration synthesis Monomers are joined by removal of OH from one monomer and removal of H from the other at the site of bond formation. H2O Monomer 1 Monomer 2 Hydrolysis Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other. H2O Monomers linked by covalent bond Example reactions Monomers linked by covalent bond Monomer 1 Dehydration synthesis of sucrose and its breakdown by hydrolysis Water is released Water is consumed Glucose Fructose H2O H2O Sucrose Monomer 2 © 2016 Pearson Education, Ltd. 2.8 Carbohydrates • Carbohydrates include sugars and starches • Contain C, H, and O– Hydrogen and oxygen are in 2:1 ratio • Three classes– Monosaccharides: one single sugar • Monomers: smallest unit of carbohydrate– Disaccharides: two sugars– Polysaccharides: many sugars • Polymers are made up of monomers of monosaccharides © 2016 Pearson Education, Ltd. 2.8 Carbohydrates • Monosaccharides– Simple sugars containing three to seven carbon atoms– (CH2O)n: general formula • n = number of carbon atoms– Monomers of carbohydrates– Important monosaccharides • Pentose sugars– Ribose and deoxyribose • Hexose sugars– Glucose (blood sugar) © 2016 Pearson Education, Ltd. Figure 2.15a Carbohydrate molecules important to the body. Monosaccharides Example Monomers of carbohydrates Example Hexose sugars (the hexoses shown here are isomers) Pentose sugars Glucose Fructose Galactose Deoxyribose Ribose © 2016 Pearson Education, Ltd. Carbohydrates (cont.) • Disaccharides– Double sugars– Too large to pass through cell membranes– Important disaccharides • Sucrose, maltose, lactose– Formed by dehydration synthesis of two monosaccharides • glucose + fructose → sucrose + water © 2016 Pearson Education, Ltd. Figure 2.15b Carbohydrate molecules important to the body. Disaccharides Consist of two linked monosaccharides Example Sucrose, maltose, and lactose (these disaccharides are isomers) Glucose Fructose Glucose Glucose Galactose Glucose Sucrose Maltose Lactose © 2016 Pearson Education, Ltd. Carbohydrates (cont.) • Polysaccharides– Polymers of monosaccharides • Formed by dehydration synthesis of many monomers– Important polysaccharides • Starch: carbohydrate storage form used by plants • Glycogen: carbohydrate storage form used by animals– Not very soluble © 2016 Pearson Education, Ltd. Figure 2.15c Carbohydrate molecules important to the body. Polysaccharides Example Long chains (polymers) of linked monosaccharides This polysaccharide is a simplified representation of glycogen, a polysaccharide formed from glucose molecules. Glycogen *Notice that in Figure 2.15 the carbon (C) atoms present at the angles of the carbohydrate ring structures are not illustrated and in Figure 2.15c only the oxygen atoms and one CH2group are shown. The illustrations at right give an example of this shorthand style: The full structure of glucose is on the left and the shorthand structure on the right. This style is used for nearly all organic ringlike structures illustrated in this chapter. © 2016 Pearson Education, Ltd. 2.9 Lipids • Contain C, H, O, but less than in carbohydrates, and sometimes contain P • Insoluble in water • Main types:– Triglycerides or neutral fats– Phospholipids– Steroids– Eicosanoids © 2016 Pearson Education, Ltd. Lipids (cont.) • Triglycerides or neutral fats– Called fats when solid and oils when liquid– Composed of three fatty acidsbonded to a glycerol molecule– Main functions • Energy storage • Insulation • Protection © 2016 Pearson Education, Ltd. Lipids (cont.) • Triglycerides can be constructed of:– Saturated fatty acids • All carbons are linked via single covalent bonds, resulting in a molecule with the maximum number of H atoms (saturated with H) • Solid at room temperature (Example: animal fats, butter)– Unsaturated fatty acids • One or more carbons are linked via double bonds, resulting in reduced H atoms (unsaturated) • Li...