Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
2 The Chemical Level of Organization PowerPoint® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris © 2012 Pearson Education, Inc. An Introduction to the Chemical Level of Organization • Learning Outcomes • 2-1 Describe an atom and how atomic structure affects interactions between atoms. • 2-2 Compare the ways in which atoms combine to form molecules and compounds. • 2-3 Distinguish among the major types of chemical reactions that are important for studying physiology. • 2-4 Describe the crucial role of enzymes in metabolism. © 2012 Pearson Education, Inc. An Introduction to the Chemical Level of Organization • Learning Outcomes • 2-5 Distinguish between organic and inorganic compounds. • 2-6 Explain how the chemical properties of water make life possible. • 2-7 Discuss the importance of pH and the role of buffers in body fluids. • 2-8 Describe the physiological roles of inorganic compounds. • 2-9 Discuss the structures and functions of carbohydrates. © 2012 Pearson Education, Inc. An Introduction to the Chemical Level of Organization • Learning Outcomes • 2-10 Discuss the structures and functions of lipids. • 2-11 Discuss the structures and functions of proteins. • 2-12 Discuss the structures and functions of nucleic acids. • 2-13 Discuss the structures and functions of highenergy compounds. • 2-14 Explain the relationship between chemicals and cells. © 2012 Pearson Education, Inc. An Introduction to the Chemical Level of Organization • Chemistry • Is the science of change • Topics of this chapter include: • The structure of atoms • The basic chemical building blocks • How atoms combine to form increasingly complex structures © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Matter • Is made up of atoms • Atoms join together to form chemicals with different characteristics • Chemical characteristics determine physiology at the molecular and cellular levels © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Subatomic Particles • Proton • Positive charge, 1 mass unit • Neutron • Neutral, 1 mass unit • Electron • Negative charge, low mass © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Atomic Structure • Atomic number • Number of protons • Nucleus • Contains protons and neutrons • Electron cloud • Contains electrons © 2012 Pearson Education, Inc. Figure 2-1 The Structure of Hydrogen Atoms Electron shell Hydrogen-1 mass number: 1 A typical hydrogen nucleus contains a proton and no neutrons. © 2012 Pearson Education, Inc. Hydrogen-2, deuterium Hydrogen-3, tritium mass number: 2 mass number: 3 A deuterium (2H) nucleus contains a proton and a neutron. A tritium (3H) nucleus contains a pair of neutrons in addition to the proton. Table 2-1 Principal Elements in the Human Body © 2012 Pearson Education, Inc. Table 2-1 Principal Elements in the Human Body © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Elements and Isotopes • Elements are determined by the atomic number of an atom • Remember atomic number = number of protons • Elements are the most basic chemicals © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Elements and Isotopes • Isotopes are the specific version of an element based on its mass number • Mass number = number of protons plus the number of neutrons • Only neutrons are different because the number of protons determines the element © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Atomic Weights • Exact mass of all particles • Measured in moles • Average of the mass numbers of the isotopes © 2012 Pearson Education, Inc. 2-1 Atoms and Atomic Structure • Electrons and Energy Levels • Electrons in the electron cloud determine the reactivity of an atom • The electron cloud contains shells, or energy levels that hold a maximum number of electrons • Lower shells fill first • Outermost shell is the valence shell, and it determines bonding • The number of electrons per shell corresponds to the number of atoms in that row of the periodic table © 2012 Pearson Education, Inc. Figure 2-2 The Arrangement of Electrons into Energy Levels The first energy level can hold a maximum of two electrons. Hydrogen, H Atomic number: 1 Mass number: 1 1 electron © 2012 Pearson Education, Inc. Helium, He Atomic number: 2 Mass number: 4 (2 protons 2 neutrons) 2 electrons Figure 2-2 The Arrangement of Electrons into Energy Levels The second and third energy levels can each contain up to 8 electrons. Lithium, Li Atomic number: 3 Mass number: 6 (3 protons 3 neutrons) 3 electrons © 2012 Pearson Education, Inc. Neon, Ne Atomic number: 10 Mass number: 20 (10 protons 10 neutrons) 10 electrons 2-2 Molecules and Compounds • Chemical Bonds • Involve the sharing, gaining, and losing of electrons in the valence shell • Three major types of chemical bonds 1. Ionic bonds • Attraction between cations (electron donor) and anions (electron acceptor) 2. Covalent bonds • Strong electron bonds involving shared electrons 3. Hydrogen bonds • Weak polar bonds based on partial electrical attractions © 2012 Pearson Education, Inc. 2-2 Molecules and Compounds • Chemical Bonds • Form molecules and/or compounds • Molecules • Two or more atoms joined by strong bonds • Compounds • Two or more atoms OF DIFFERENT ELEMENTS joined by strong or weak bonds • Compounds are all molecules, but not all molecules are compounds • H2 = molecule only © 2012 Pearson Education, Inc. H2O = molecule and compound 2-2 Molecules and Compounds • Ionic Bonds • One atom—the electron donor—loses one or more electrons and becomes a cation, with a positive charge • Another atom—the electron acceptor—gains those same electrons and becomes an anion, with a negative charge • Attraction between the opposite charges then draws the two ions together © 2012 Pearson Education, Inc. Figure 2-3a The Formation of Ionic Bonds Formation of ions Sodium atom Attraction between opposite charges Formation of an ionic compound Sodium ion (Na) Sodium chloride (NaCl) Chlorine atom Chloride ion (Cl) 1 A sodium (Na) atom loses an electron, which is accepted by a chlorine (Cl) atom. 2 Because the sodium (Na) and chloride (Cl) ions have opposite charges, they are attracted to one another. 3 The association of sodium and chloride ions forms the ionic compound sodium chloride. Formation of an ionic bond. © 2012 Pearson Education, Inc. Figure 2-3b The Formation of Ionic Bonds Chloride ions (Cl) © 2012 Pearson Education, Inc. Sodium ions (Na) Sodium chloride crystal. Large numbers of sodium and chloride ions form a crystal of sodium chloride (table salt). 2-2 Molecules and Compounds • Covalent Bonds • Involve the sharing of pairs of electrons between atoms • One electron is donated by each atom to make the pair of electrons • Sharing one pair of electrons is a single covalent bond • Sharing two pairs of electrons is a double covalent bond • Sharing three pairs of electrons is a triple covalent bond © 2012 Pearson Education, Inc. Figure 2-4 Covalent Bonds in Four Common Molecules Molecule Electron Shell Model and Structural Formula Hydrogen (H2) HH Oxygen (O2) OO Carbon dioxide (CO2) Nitric oxide (NO) © 2012 Pearson Education, Inc. OCO NO 2-2 Molecules and Compounds • Covalent Bonds • Nonpolar covalent bonds • Involve equal sharing of electrons because atoms involved in the bond have equal pull for the electrons • Polar covalent bonds • Involve the unequal sharing of electrons because one of the atoms involved in the bond has a disproportionately strong pull on the electrons • Form polar molecules — like water © 2012 Pearson Education, Inc. Figure 2-5 Polar Covalent Bonds and the Structure of Water Hydrogen atom Hydrogen atom Oxygen atom Hydrogen atom Oxygen atom 2 © 2012 Pearson Education, Inc. 2-2 Molecules and Compounds • Hydrogen Bonds • Bonds between adjacent molecules, not atoms • Involve slightly positive and slightly negative portions of polar molecules being attracted to one another • Hydrogen bonds between H2O molecules cause surface tension © 2012 Pearson Education, Inc. 2-2 Molecules and Compounds • States of Matter • Solid • Constant volume and shape • Liquid • Constant volume but changes shape • Gas • Changes volume and shape © 2012 Pearson Education, Inc. 2-2 Molecules and Compounds • Molecular Weights • The molecular weight of a molecule is the sum of the atomic weights of its component atoms • H = approximately 1 • O = approximately 16 • H2 = approximately 2 • H2O = approximately 18 © 2012 Pearson Education, Inc. 2-3 Chemical Reactions • In a Chemical Reaction • Either new bonds are formed or existing bonds are broken • Reactants • Materials going into a reaction • Products • Materials coming out of a reaction • Metabolism • All of the reactions that are occurring at one time © 2012 Pearson Education, Inc. Figure 2-7 Chemical Notation Atoms The symbol of an element indicates one atom of that element. A number preceding the symbol of an element indicates more than one atom of that element. VISUAL REPRESENTATION CHEMICAL NOTATION one atom of hydrogen one atom of oxygen one atom one atom of hydrogen of oxygen two atoms of hydrogen two atoms of oxygen two atoms two atoms of hydrogen of oxygen © 2012 Pearson Education, Inc. Figure 2-7 Chemical Notation Molecules A subscript following the symbol of an element indicates a molecule with that number of atoms of that element. VISUAL REPRESENTATION hydrogen molecule composed of two hydrogen atoms oxygen molecule composed of two oxygen atoms water molecule composed of two hydrogen atoms and one oxygen atom © 2012 Pearson Education, Inc. CHEMICAL NOTATION hydrogen oxygen molecule molecule water molecule Figure 2-7 Chemical Notation Reactions In a description of a chemical reaction, the participants at the start of the reaction are called reactants, and the reaction generates one or more products. An arrow indicates the direction of the reaction, from reactants (usually on the left) to products (usually on the right). In the following reaction, two atoms of hydrogen combine with one atom of oxygen to produce a single molecule of water. VISUAL REPRESENTATION Chemical reactions neither create nor destroy atoms; they merely rearrange atoms into new combinations. Therefore, the numbers of atoms of each element must always be the same on both sides of the equation for a chemical reaction. When this is the case, the equation is balanced. © 2012 Pearson Education, Inc. CHEMICAL NOTATION Balanced equation Unbalanced equation Figure 2-7 Chemical Notation Ions A superscript plus or minus sign following the symbol of an element indicates an ion. A single plus sign indicates a cation with a charge of 1. (The original atom has lost one electron.) A single minus sign indicates an anion with a charge of 1. (The original atom has gained one electron.) If more than one electron has been lost or gained, the charge on the ion is indicated by a number preceding the plus or minus sign. VISUAL REPRESENTATION sodium ion chloride ion the sodium the chlorine atom has lost atom has gained one electron one electron A sodium atom becomes a sodium ion Electron lost Sodium atom (Na) Sodium ion (Na) © 2012 Pearson Education, Inc. calcium ion the calcium atom has lost two electrons CHEMICAL NOTATION sodium ion chloride ion calcium ion 2-3 Chemical Reactions • Basic Energy Concepts • Energy • The power to do work • Work • A change in mass or distance • Kinetic energy • Energy of motion • Potential energy • Stored energy • Chemical energy • Potential energy stored in chemical bonds © 2012 Pearson Education, Inc. 2-3 Chemical Reactions • Types of Chemical Reactions 1. Decomposition reaction (catabolism) 2. Synthesis reaction (anabolism) 3. Exchange reaction 4. Reversible reaction © 2012 Pearson Education, Inc. 2-3 Chemical Reactions • Decomposition Reaction (Catabolism) • Breaks chemical bonds • AB A + B • Hydrolysis A-B + H2O A-H + HO-B • Synthesis Reaction (Anabolism) • Forms chemical bonds • A + B AB • Dehydration synthesis (condensation reaction) A-H + HO-B A-B + H2O © 2012 Pearson Education, Inc. 2-3 Chemical Reactions • Exchange Reaction • Involves decomposition first, then synthesis • AB + CD AD + CB © 2012 Pearson Education, Inc. 2-3 Chemical Reactions • Reversible Reaction • A + B AB • At equilibrium the amounts of chemicals do not change even though the reactions are still occurring • Reversible reactions seek equilibrium, balancing opposing reaction rates • Add or remove reactants • Reaction rates adjust to reach a new equilibrium © 2012 Pearson Education, Inc. 2-4 Enzymes • Chemical Reactions • In cells cannot start without help • Activation energy is the amount of energy needed to get a reaction started • Enzymes are protein catalysts that lower the activation energy of reactions © 2012 Pearson Education, Inc. Figure 2-8 The Effect of Enzymes on Activation Energy Activation energy required Energy Without enzyme With enzyme Reactants Stable product Progress of reaction © 2012 Pearson Education, Inc. 2-4 Enzymes • Exergonic (Exothermic) Reactions • Produce more energy than they use • Endergonic (Endothermic) Reactions • Use more energy than they produce ANIMATION Chemical Reactions: Enzymes © 2012 Pearson Education, Inc. 2-5 Organic and Inorganic Compounds • Nutrients • Essential molecules obtained from food • Metabolites • Molecules made or broken down in the body • Inorganic Compounds • Molecules not based on carbon and hydrogen • Carbon dioxide, oxygen, water, and inorganic acids, bases, and salts • Organic Compounds • Molecules based on carbon and hydrogen • Carbohydrates, proteins, lipids, and nucleic acids © 2012 Pearson Education, Inc. 2-6 Properties of Water • Water • Accounts for up to two-thirds of your total body weight • A solution is a uniform mixture of two or more substances • It consists of a solvent, or medium, in which atoms, ions, or molecules of another substance, called a solute, are individually dispersed © 2012 Pearson Education, Inc. 2-6 Properties of Water • Solubility • Water’s ability to dissolve a solute in a solvent to make a solution • Reactivity • Most body chemistry occurs in water • High Heat Capacity • Water’s ability to absorb and retain heat • Lubrication • To moisten and reduce friction © 2012 Pearson Education, Inc. 2-6 Properties of Water • The Properties of Aqueous Solutions • Ions and polar compounds undergo ionization, or dissociation in water • Polar water molecules form hydration spheres around ions and small polar molecules to keep them in solution © 2012 Pearson Education, Inc. Figure 2-9 The Activities of Water Molecules in Aqueous Solutions Hydration spheres Negative pole H Cl Positive pole © 2012 Pearson Education, Inc. Na Glucose molecule Figure 2-9a The Activities of Water Molecules in Aqueous Solutions Negative pole H Positive pole Water molecule. In a water molecule, oxygen forms polar covalent bonds with two hydrogen atoms. Because both hydrogen atoms are at one end of the molecule, it has an uneven distribution of charges, creating positive and negative poles. © 2012 Pearson Education, Inc. Figure 2-9b The Activities of Water Molecules in Aqueous Solutions Hydration spheres Cl Na © 2012 Pearson Education, Inc. Sodium chloride in solution. Ionic compounds, such as sodium chloride, dissociate in water as the polar water molecules break the ionic bonds in the large crystal structure. Each ion in solution is surrounded by water molecules, creating hydration spheres. Figure 2-9c The Activities of Water Molecules in Aqueous Solutions Glucose molecule © 2012 Pearson Education, Inc. Glucose in solution. Hydration spheres also form around an organic molecule containing polar covalent bonds. If the molecule binds water strongly, as does glucose, it will be carried into solution—in other words, it will dissolve. Note that the molecule does not dissociate, as occurs for ionic compounds. Table 2-2 Important Electrolytes that Dissociate in Body Fluids © 2012 Pearson Education, Inc. 2-6 Properties of Water • The Properties of Aqueous Solutions • Electrolytes and body fluids • Electrolytes are inorganic ions that conduct electricity in solution • Electrolyte imbalance seriously disturbs vital body functions © 2012 Pearson Education, Inc. 2-6 Properties of Water • The Properties of Aqueous Solutions • Hydrophilic and hydrophobic compounds • Hydrophilic • hydro- = water, philos = loving • Interacts with water • Includes ions and polar molecules • Hydrophobic • phobos = fear • Does NOT interact with water • Includes nonpolar molecules, fats, and oils © 2012 Pearson Education, Inc. 2-6 Properties of Water • Colloids and Suspensions • Colloid • A solution of very large organic molecules • For example, blood plasma • Suspension • A solution in which particles settle (sediment) • For example, whole blood • Concentration • The amount of solute in a solvent (mol/L, mg/mL) © 2012 Pearson Education, Inc. 2-7 pH and Homeostasis • pH • The concentration of hydrogen ions (H+) in a solution • Neutral pH • A balance of H+ and OH • Pure water = 7.0 © 2012 Pearson Education, Inc. 2-7 pH and Homeostasis • Acidic pH Lower Than 7.0 • High H+ concentration • Low OH concentration • Basic (or alkaline) pH Higher Than 7.0 • Low H+ concentration • High OH concentration • pH of Human Blood • Ranges from 7.35 to 7.45 © 2012 Pearson Education, Inc. 2-7 pH and Homeostasis • pH Scale • Has an inverse relationship with H+ concentration • More H+ ions mean lower pH, less H+ ions mean higher pH © 2012 Pearson Education, Inc. Figure 2-10 pH and Hydrogen Ion Concentration 1 mol/L hydrochloric acid Beer, vinegar, wine, Tomatoes, pickles grapes Stomach acid Extremely acidic pH 0 [H] 100 (mol/L) 1 101 Urine Saliva, milk Increasing concentration of H 2 102 3 103 © 2012 Pearson Education, Inc. 4 104 5 105 1 mol/L sodium hydroxide 6 106 Blood Ocean Household Pure Eggswater bleach water Neutral 7 107 Household ammonia Increasing concentration of OH 8 108 9 109 10 1010 11 1011 12 1012 Oven cleaner Extremely basic 13 1013 14 1014 2-8 Inorganic Compounds • Acid • A solute that adds hydrogen ions to a solution • Proton donor • Strong acids dissociate completely in solution • Base • A solute that removes hydrogen ions from a solution • Proton acceptor • Strong bases dissociate completely in solution • Weak Acids and Weak Bases • Fail to dissociate completely • Help to balance the pH © 2012 Pearson Education, Inc. 2-8 Inorganic Compounds • Salts • Solutes that dissociate into cations and anions other than hydrogen ions and hydroxide ions © 2012 Pearson Education, Inc. 2-8 Inorganic Compounds • Buffers and pH Control • Buffers • Weak acid/salt compounds • Neutralize either strong acid or strong base • Sodium bicarbonate is very important in humans • Antacids • Basic compounds that neutralize acid and form a salt • Alka-Seltzer, Tums, Rolaids, etc. © 2012 Pearson Education, Inc. 2-9 Carbohydrates • Organic Molecules • Contain H, C, and usually O • Are covalently bonded • Contain functional groups that determine chemistry • Carbohydrates • Lipids • Proteins (or amino acids) • Nucleic acids © 2012 Pearson Education, Inc. Table 2-3 Important Functional Groups of Organic Compounds © 2012 Pearson Education, Inc. 2-9 Carbohydrates • Carbohydrates • Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio • Monosaccharide — simple sugar • Disaccharide — two sugars • Polysaccharide — many sugars © 2012 Pearson Education, Inc. 2-9 Carbohydrates • Monosaccharides • Simple sugars with 3 to 7 carbon atoms • Glucose, fructose, galactose • Disaccharides • Two simple sugars condensed by dehydration synthesis • Sucrose, maltose • Polysaccharides • Many monosaccharides condensed by dehydration synthesis • Glycogen, starch, cellulose © 2012 Pearson Education, Inc. Figure 2-12a The Formation and Breakdown of Complex Sugars DEHYDRATION SYNTHESIS Glucose Fructose © 2012 Pearson Education, Inc. Sucrose Figure 2-12a The Formation and Breakdown of Complex Sugars DEHYDRATION SYNTHESIS Glucose Fructose Formation of the disaccharide sucrose through dehydration synthesis. © 2012 Pearson Education, Inc. Figure 2-12a The Formation and Breakdown of Complex Sugars DEHYDRATION SYNTHESIS Sucrose During dehydration synthesis, two molecules are joined by the removal of a water molecule. © 2012 Pearson Education, Inc. Figure 2-12b The Formation and Breakdown of Complex Sugars HYDROLYSIS Sucrose © 2012 Pearson Education, Inc. Glucose Fructose Figure 2-12b The Formation and Breakdown of Complex Sugars HYDROLYSIS Sucrose Breakdown of sucrose into simple sugars by hydrolysis. © 2012 Pearson Education, Inc. Figure 2-12b The Formation and Breakdown of Complex Sugars HYDROLYSIS Glucose Fructose Hydrolysis reverses the steps of dehydration synthesis; a complex molecule is broken down by the addition of a water molecule. © 2012 Pearson Education, Inc. Figure 2-13 The Structure of the Polysaccharide Glycogen Glucose molecules © 2012 Pearson Education, Inc. Table 2-4 Carbohydrates in the Body © 2012 Pearson Education, Inc. 2-10 Lipids • Lipids • Mainly hydrophobic molecules such as fats, oils, and waxes • Made mostly of carbon and hydrogen atoms • Include: • Fatty acids • Eicosanoids • Glycerides • Steroids • Phospholipids and glycolipids © 2012 Pearson Education, Inc. 2-10 Lipids • Fatty Acids • Long chains of carbon and hydrogen with a carboxyl group (COOH) at one end • Are relatively nonpolar, except the carboxyl group • Fatty acids may be: • Saturated with hydrogen (no covalent bonds) • Unsaturated (one or more double bonds) • Monounsaturated = one double bond • Polyunsaturated = two or more double bonds © 2012 Pearson Education, Inc. Figure 2-14b Fatty Acids Saturated Unsaturated A fatty acid is either saturated (has single covalent bonds only) or unsaturated (has one or more double covalent bonds). The presence of a double bond causes a sharp bend in the molecule. © 2012 Pearson Education, Inc. 2-10 Lipids • Eicosanoids • Derived from the fatty acid called arachidonic acid • Leukotrienes • Active in immune system • Prostaglandins • Local hormones, short-chain fatty acids © 2012 Pearson Education, Inc. 2-10 Lipids • Glycerides • Fatty acids attached to a glycerol molecule • Triglycerides are the three fatty-acid tails • Also called triacylglycerols or neutral fats • Have three important functions 1. Energy source 2. Insulation 3. Protection © 2012 Pearson Education, Inc. Figure 2-16 Triglyceride Formation Glycerol Fatty acids Fatty Acid 1 Saturated Fatty Acid 2 Saturated Fatty Acid 3 Unsaturated DEHYDRATION SYNTHESIS © 2012 Pearson Education, Inc. HYDROLYSIS Triglyceride 2-10 Lipids • Steroids • Four rings of carbon and hydrogen with an assortment of functional groups • Types of steroids: • Cholesterol • Component of plasma (cell) membranes • Estrogens and testosterone • Sex hormones • Corticosteroids and calcitriol • Metabolic regulation • Bile salts • Derived from steroids © 2012 Pearson Education, Inc. Figure 2-17 Steroids Cholesterol Estrogen © 2012 Pearson Education, Inc. Testosterone 2-10 Lipids • Phospholipids and Glycolipids • Diglycerides attached to either a phosphate group (phospholipid) or a sugar (glycolipid) • Generally, both have hydrophilic heads and hydrophobic tails and are structural lipids, components of plasma (cell) membranes © 2012 Pearson Education, Inc. Figure 2-18b Phospholipids and Glycolipids Carbohydrate Fatty acids © 2012 Pearson Education, Inc. In a glycolipid, a carbohydrate is attached to a diglyceride. Table 2-5 Representative Lipids and Their Functions in the Body © 2012 Pearson Education, Inc. 2-11 Proteins • Proteins • Are the most abundant and important organic molecules • Contain basic elements • Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) • Basic building blocks • 20 amino acids © 2012 Pearson Education, Inc. 2-11 Proteins • Seven Major Protein Functions 1. Support • Structural proteins 2. Movement • Contractile proteins 3. Transport • Transport (carrier) proteins 4. Buffering • Regulation of pH 5. Metabolic Regulation • Enzymes 6. Coordination and Control • Hormones 7. Defense • © 2012 Pearson Education, Inc. Antibodies 2-11 Proteins • Protein Structure • Long chains of amino acids • Five components of amino acid structure 1. Central carbon atom 2. Hydrogen atom 3. Amino group (—NH2) 4. Carboxyl group (—COOH) 5. Variable side chain or R group © 2012 Pearson Education, Inc. Figure 2-19 Amino Acids Structure of an Amino Acid Amino group Central carbon Carboxyl group R group (variable side chain of one or more atoms) © 2012 Pearson Education, Inc. 2-11 Proteins • Hooking Amino Acids Together • Requires a dehydration synthesis between: • The amino group of one amino acid and the carboxyl group of another amino acid • Forms a peptide bond • Resulting molecule is a peptide © 2012 Pearson Education, Inc. Figure 2-20 The Fomation of Peptide Bonds Peptide Bond Formation Glycine (gly) DEHYDRATION SYNTHESIS © 2012 Pearson Education, Inc. Alanine (ala) HYDROLYSIS Peptide bond 2-11 Proteins • Protein Shape • Primary structure • The sequence of amino acids along a polypeptide • Secondary structure • Hydrogen bonds form spirals or pleats • Tertiary structure • Secondary structure folds into a unique shape • Quaternary structure • Final protein shape — several tertiary structures together © 2012 Pearson Education, Inc. Figure 2-21 Protein Structure A1 A3 A2 A5 A4 A7 A6 A8 A9 Linear chain of amino acids A1 A1 A6 A3 A3 A4 Hydrogen bond Hydrogen bond A2 A2 A5 A5 A9 A8 A7 A6 A11 A12 A13 A14 A10 A7 A9 Alpha-helix OR Pleated sheet OR Heme units Hemoglobin (globular protein) © 2012 Pearson Education, Inc. Keratin or collagen (fibrous protein) Figure 2-21ab Protein Structure A1 A2 A3 A5 A4 A6 A7 A8 Linear chain of amino acids Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and Hydrogen so on) along bond its length. A2 A1 A6 A3 A5 A7 A9 Alpha-helix Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral (an alpha-helix) or a flattened arrangement known as a pleated sheet. © 2012 Pearson Education, Inc. A9 Figure 2-21ab Protein Structure A1 A2 A3 A4 A7 A6 A5 A9 A8 Linear chain of amino acids Primary structure. The primary structure of a polypeptide is the sequence of amino acids (A1, A2, A3, and so on) along its length. A1 A2 A3 A4 Hydrogen bond A5 A9 A8 A7 A6 A11 A12 A13 A14 A10 Pleated sheet Secondary structure. Secondary structure is primarily the result of hydrogen bonding along the length of the polypeptide chain. Such bonding often produces a simple spiral (an alpha-helix) or a flattened arrangement known as a pleated sheet. © 2012 Pearson Education, Inc. Figure 2-21cd Protein Structure Heme units Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Hemoglobin (globular protein) Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. A single hemoglobin molecule contains four globular subunits. © 2012 Pearson Education, Inc. Figure 2-21cd Protein Structure Heme units Tertiary structure. Tertiary structure is the coiling and folding of a polypeptide. Keratin or collagen (fibrous protein) Quaternary structure. Quaternary structure develops when separate polypeptide subunits interact to form a larger molecule. © 2012 Pearson Education, Inc. 2-11 Proteins • Fibrous Proteins • Structural sheets or strands • Globular Proteins • Soluble spheres with active functions • Protein function is based on shape • Shape is based on sequence of amino acids © 2012 Pearson Education, Inc. Figure 2-21d Protein Structure OR Heme units Hemoglobin (globular protein) © 2012 Pearson Education, Inc. Keratin or collagen (fibrous protein) 2-11 Proteins • Enzyme Function • Enzymes are catalysts • Proteins that lower the activation energy of a chemical reaction • Are not changed or used up in the reaction • Enzymes also exhibit: 1. Specificity — will only work on limited types of substrates 2. Saturation Limits — by their concentration 3. Regulation — by other cellular chemicals © 2012 Pearson Education, Inc. Figure 2-22 A Simplified View of Enzyme Structure and Function Substrates bind to active site of enzyme © 2012 Pearson Education, Inc. Figure 2-22 A Simplified View of Enzyme Structure and Function Once bound to the active site, the substrates are held together and their interaction facilitated Enzyme-substrate complex © 2012 Pearson Education, Inc. Figure 2-22 A Simplified View of Enzyme Structure and Function Substrate binding alters the shape of the enzyme, and this change promotes product formation © 2012 Pearson Education, Inc. Figure 2-22 A Simplified View of Enzyme Structure and Function Product detaches from enzyme; entire process can now be repeated © 2012 Pearson Education, Inc. 2-11 Proteins • Cofactors and Enzyme Function • Cofactor • An ion or molecule that binds to an enzyme before substrates can bind • Coenzyme • Nonprotein organic cofactors (vitamins) • Isozymes • Two enzymes that can catalyze the same reaction © 2012 Pearson Education, Inc. 2-11 Proteins • Effects of Temperature and pH on Enzyme Function • Denaturation • Loss of shape and function due to heat or pH © 2012 Pearson Education, Inc. 2-11 Proteins • Glycoproteins and Proteoglycans • Glycoproteins • Large protein + small carbohydrate • Includes enzymes, antibodies, hormones, and mucus production • Proteoglycans • Large polysaccharides + polypeptides • Promote viscosity © 2012 Pearson Education, Inc. 2-12 Nucleic Acids • Nucleic Acids • Are large organic molecules, found in the nucleus, which store and process information at the molecular level • Deoxyribonucleic acid (DNA) • Determines inherited characteristics • Directs protein synthesis • Controls enzyme production • Controls metabolism • Ribonucleic acid (RNA) • Controls intermediate steps in protein synthesis © 2012 Pearson Education, Inc. 2-12 Nucleic Acids • Structure of Nucleic Acids • DNA and RNA are strings of nucleotides • Nucleotides • Are the building blocks of DNA and RNA • Have three molecular parts 1. A pentose sugar (deoxyribose or ribose) 2. Phosphate group 3. Nitrogenous base (A, G, T, C, or U) © 2012 Pearson Education, Inc. Figure 2-23a Nucleotides and Nitrogenous Bases Generic nucleotide The nitrogenous base may be a purine or a pyrimidine. Sugar Phosphate group © 2012 Pearson Education, Inc. Nitrogenous base Figure 2-23b Nucleotides and Nitrogenous Bases Purines Adenine Guanine © 2012 Pearson Education, Inc. Figure 2-23c Nucleotides and Nitrogenous Bases Pyrimidines Cytosine Thymine (DNA only) Uracil (RNA only) © 2012 Pearson Education, Inc. 2-12 Nucleic Acids • DNA and RNA • DNA is double stranded, and the bases form hydrogen bonds to hold the DNA together • Sometimes RNA can bind to itself but is usually a single strand • DNA forms a twisting double helix • Complementary base pairs • Purines pair with pyrimidines • DNA • Adenine (A) and thymine (T) • Cytosine (C) and guanine (G) • RNA • Uracil (U) replaces thymine (T) © 2012 Pearson Education, Inc. Figure 2-24 The Structure of Nucleic Acids Phosphate group Deoxyribose Adenine Thymine Hydrogen bond DNA strand 1 DNA strand 2 RNA molecule. Cytosine DNA molecule. © 2012 Pearson Education, Inc. Guanine 2-12 Nucleic Acids • Types of RNA • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA) © 2012 Pearson Education, Inc. Table 2-6 Comparison of RNA with DNA © 2012 Pearson Education, Inc. 2-13 High-Energy Compounds • Nucleotides Can Be Used to Store Energy • Adenosine diphosphate (ADP) • Two phosphate groups; di- = 2 • Adenosine triphosphate (ATP) • Three phosphate groups; tri- = 3 • Phosphorylation • Adding a phosphate group to ADP with a high-energy bond to form the high-energy compound ATP • Adenosine triphosphatase (ATPase) • The enzyme that catalyzes the conversion of ATP to ADP © 2012 Pearson Education, Inc. Figure 2-25 The Structure of ATP Adenine Ribose Phosphate Phosphate Phosphate High-energy bonds Adenosine Adenosine monophosphate (AMP) Adenosine diphosphate (ADP) Adenosine triphosphate (ATP) Adenine Phosphate groups Ribose Adenosine © 2012 Pearson Education, Inc. 2-14 Chemicals and Cells • Chemicals and Cells • Biochemical building blocks form functional units called cells • Metabolic turnover lets your body grow, change, and adapt to new conditions and activities • Your body recycles and renews all of its chemical components at intervals ranging from minutes to years © 2012 Pearson Education, Inc. Table 2-7 Classes of Inorganic and Organic Compounds © 2012 Pearson Education, Inc. Table 2-8 Turnover Times © 2012 Pearson Education, Inc.