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Biochemistry Organic compounds Contain carbon, are covalently bonded, and are often large Inorganic compounds Do not contain carbon Water, salts, and many acids and bases Properties of Water High heat capacity – absorbs and releases large amounts of heat before changing temperature High heat of vaporization – changing from a liquid to a gas requires large amounts of heat Polar solvent properties – dissolves ionic substances, forms hydration layers around large charged molecules, and serves as the body’s major transport medium Properties of Water Reactivity – is an important part of hydrolysis and dehydration synthesis reactions Cushioning – resilient cushion around certain body organs PLAY InterActive Physiology®: Fluid, Electrolyte, and Acid/Base Balance: Introduction to Body Fluids Salts Inorganic compounds Contain cations other than H+ and anions other than OH– Are electrolytes; they conduct electrical currents Acids and Bases Acids release H+ and are therefore proton donors HCl H+ + Cl – Bases release OH– and are proton acceptors NaOH Na+ + OH– Acid-Base Concentration (pH) Acidic solutions have higher H+ concentration and therefore a lower pH Alkaline solutions have lower H+ concentration and therefore a higher pH Neutral solutions have equal H+ and OH– concentrations Acid-Base Concentration (pH) Acidic: pH 0–6.99 Basic: pH 7.01–14 Neutral: pH 7.00 Figure 2.13 Buffers Systems that resist abrupt and large swings in the pH of body fluids Carbonic acid-bicarbonate system PLAY Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood InterActive Physiology®: Fluid, Electrolyte, and Acid/Base Balance: Acid/Base Homeostasis Organic Compounds Molecules unique to living systems contain carbon and hence are organic compounds They include: Carbohydrates Lipids Proteins Nucleic Acids Carbohydrates Contain carbon, hydrogen, and oxygen Their major function is to supply a source of cellular food Examples: Monosaccharides or simple sugars Figure 2.14a Carbohydrates Disaccharides or double sugars PLAY Disaccharides Figure 2.14b Carbohydrates Polysaccharides or polymers of simple sugars PLAY Polysaccharides Figure 2.14c Lipids Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates Examples: PLAY Neutral fats or triglycerides Phospholipids Steroids Eicosanoids Fats Neutral Fats (Triglycerides) Composed of three fatty acids bonded to a glycerol molecule Figure 2.15a Other Lipids Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group Figure 2.15b Other Lipids Steroids – flat molecules with four interlocking hydrocarbon rings Eicosanoids – 20-carbon fatty acids found in cell membranes Figure 2.15c Representative Lipids Found in the Body Neutral fats – found in subcutaneous tissue and around organs Phospholipids – chief component of cell membranes Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones Representative Lipids Found in the Body Fat-soluble vitamins – vitamins A, E, and K Eicosanoids – prostaglandins, leukotrienes, and thromboxanes Lipoproteins – transport fatty acids and cholesterol in the bloodstream Amino Acids Building blocks of protein, containing an amino group and a carboxyl group Amino group NH2 Carboxyl groups COOH Amino Acids Figure 2.16a–c Amino Acids Figure 2.16d, e Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond H H R O N C C OH H Amino acid + H H R O N C C OH H Amino acid Dehydration H O 2 synthesis Hydrolysis H H2O H R O H R O N C C N C C H H OH Dipeptide Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds H H R O N C C OH H Amino acid + H H R O N C C OH H Amino acid Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds H H R O N C C OH H Amino acid + H H R O N C C Dehydration H O 2 synthesis OH H Amino acid Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond H H R O N C C OH H Amino acid + H H R O N C C OH H Amino acid Dehydration H O 2 synthesis H H R O H R O N C C N C C H H OH Dipeptide Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond H H R O H R O N C C N C C H H OH Dipeptide Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond Hydrolysis H H2O H R O H R O N C C N C C H H OH Dipeptide Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond H H R O N C C OH H Amino acid + H H R O H R O H R O N C C N C C N C C OH H Amino acid Hydrolysis H H2O H H OH Dipeptide Figure 2.17 Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Peptide bond H H R O N C C OH H Amino acid + H H R O N C C OH H Amino acid Dehydration H O 2 synthesis Hydrolysis H H2O H R O H R O N C C N C C H H OH Dipeptide Figure 2.17 Structural Levels of Proteins Primary – amino acid sequence Secondary – alpha helices or beta pleated sheets PLAY Chemistry of Life: Introduction to Protein Structure PLAY Chemistry of Life: Proteins: Primary Structure PLAY Chemistry of Life: Proteins: Secondary Structure Structural Levels of Proteins Tertiary – superimposed folding of secondary structures Quaternary – polypeptide chains linked together in a specific manner PLAY Chemistry of Life: Proteins: Tertiary Structure PLAY Chemistry of Life: Proteins: Quaternary Structure Structural Levels of Proteins Figure 2.18a–c Structural Levels of Proteins Figure 2.18b,d,e Fibrous and Globular Proteins Fibrous proteins Extended and strand-like proteins Examples: keratin, elastin, collagen, and certain contractile fibers Fibrous and Globular Proteins Globular proteins Compact, spherical proteins with tertiary and quaternary structures Examples: antibodies, hormones, and enzymes Protein Denuaturation Reversible unfolding of proteins due to drops in pH and/or increased temperature Figure 2.19a Protein Denuaturation Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes Figure 2.19b Molecular Chaperones (Chaperonins) Help other proteins to achieve their functional three-dimensional shape Maintain folding integrity Assist in translocation of proteins across membranes Promote the breakdown of damaged or denatured proteins Characteristics of Enzymes Most are globular proteins that act as biological catalysts Holoenzymes consist of an apoenzyme (protein) and a cofactor (usually an ion) Enzymes are chemically specific Characteristics of Enzymes Frequently named for the type of reaction they catalyze Enzyme names usually end in -ase Lower activation energy Characteristics of Enzymes Figure 2.20 Mechanism of Enzyme Action Enzyme binds with substrate Product is formed at a lower activation energy Product is released PLAY How Enzymes Work Active site Amino acids + Enzyme (E) Substrates (S) Enzyme-substrate complex (E-S) H2O Free enzyme (E) Peptide bond Internal rearrangements leading to catalysis Dipeptide product (P) Figure 2.21 Active site Amino acids + Enzyme (E) Substrates (S) Enzyme-substrate complex (E-S) H2O Figure 2.21 Active site Amino acids + Enzyme (E) Substrates (S) Enzyme-substrate complex (E-S) H2O Internal rearrangements leading to catalysis Figure 2.21 Active site Amino acids + Enzyme (E) Substrates (S) Enzyme-substrate complex (E-S) H2O Free enzyme (E) Peptide bond Internal rearrangements leading to catalysis Dipeptide product (P) Figure 2.21 Nucleic Acids Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group Nucleic Acids Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) Two major classes – DNA and RNA Deoxyribonucleic Acid (DNA) Double-stranded helical molecule found in the nucleus of the cell Replicates itself before the cell divides, ensuring genetic continuity Provides instructions for protein synthesis Structure of DNA Figure 2.22a Structure of DNA Figure 2.22b Ribonucleic Acid (RNA) Single-stranded molecule found in both the nucleus and the cytoplasm of a cell Uses the nitrogenous base uracil instead of thymine Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA Adenosine Triphosphate (ATP) Source of immediately usable energy for the cell Adenine-containing RNA nucleotide with three phosphate groups Adenosine Triphosphate (ATP) Figure 2.23 Membrane protein Pi P Solute Solute transported (a) Transport work ADP + Pi ATP Relaxed smooth muscle cell Contracted smooth muscle cell (b) Mechanical work Pi X P X Y + Y Reactants Product made (c) Chemical work Figure 2.24 Membrane protein P Solute (a) Transport work ATP Figure 2.24 Membrane protein Pi P Solute Solute transported (a) Transport work ATP ADP + Pi Figure 2.24 ATP Relaxed smooth muscle cell (b) Mechanical work Figure 2.24 ADP + Pi ATP Relaxed smooth muscle cell Contracted smooth muscle cell (b) Mechanical work Figure 2.24 ATP X P + Y Reactants (c) Chemical work Figure 2.24 ADP + Pi ATP Pi X P X Y + Y Reactants Product made (c) Chemical work Figure 2.24 Membrane protein Pi P Solute Solute transported (a) Transport work ADP + Pi ATP Relaxed smooth muscle cell Contracted smooth muscle cell (b) Mechanical work Pi X P X Y + Y Reactants Product made (c) Chemical work Figure 2.24