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Chemistry Comes Alive Part B Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb 2 Categories of Molecules Organic molecules Contain carbon Covalent bonds Produced by living or once living organisms Inorganic molecules Typically do not contain carbon Include: Water, ammonia, salts, and some acids and bases Salts Electrolytes conduct electrical currents Examples: NaCl, KCl, CaCl2, Ca3(PO4)2 Acids and Bases Acids release H+ HCl H+ + Cl – Bases release OH– NaOH Na+ + OH– Acid-Base Concentration (pH) pH describes the concentration of H+ in a solution pH = -log[H+] A scale based on [H+] found in H2O is used H2O H+ + OHˉ [H+] =1x10-7M and [OHˉ] = 1x10-7M Therefore H2O has a pH = 7 Acidic solutions have [H+] higher than 1x10-7M and therefore a pH < 7 Alkaline solutions have lower [H+] concentrations and therefore a pH > 7 Acid-Base Concentration (pH) Acidic: pH 0–6.99 Neutral: pH 7.00 Basic: pH 7.01–14 Figure 2.12 Buffers Solutions of molecules that resist changes in pH pH of blood is maintained by carbonic acidbicarbonate buffering system Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood H2O + CO2 H2CO3 H+ + HCO3ˉ Organic Molecules Unique to living systems - hence organic Small molecules & macromolecules (biomolecules) Macromolecules are polymers of smaller organic molecules Major biomolecule groups Carbohydrates Lipids Proteins Nucleic Acids Carbohydrates Major functions are energy source support (plants, fungi & bacteria) parts of other macromolecules Monosaccharides or simple sugars Carbohydrates Disaccharides Carbohydrates Polysaccharides - polymers of simple sugars Each monosaccharide is a residue Glycogen - energy storage in animals Starch – energy storage in plants Cellulose – support structures in plants Figure 2.13c Carbohydrates in other Biomolecules Glycoproteins Proteins containing sugar residues Glycolipids Phospholipids with sugar residues Ribose and Deoxyribose sugars as part of nucleotides and nucleic acids Lipids Representatives Neutral fats – triglycerides - adipose tissue Phospholipids – chief component of cell membranes Steroids – cholesterol, bile salts, vitamin D, hormones Vitamins A, E & K Eicosanoids – prostaglandins Fatty Acids & Triglycerides Phospholipids Figure 2.14b Phospholipids in membranes Phospholipids make up cellular membranes (lipid bilayers) Steroid Lipids Prostaglandins Eicosanoids – Used to make prostaglandins Protein Polymers of amino acids Figure 2.16 Amino Acids Building blocks of protein, containing an amine group, a carboxyl group, & a variable side chain Structural Levels of Proteins Structural Levels of Proteins Structural Levels of Proteins Figure 2.17d, e Fibrous and Globular Proteins Fibrous proteins Extended and thread-like proteins Examples: keratin, elastin, collagen, myosin, actin Globular proteins Compact, spherical proteins with tertiary and quaternary structures Examples: antibodies, peptide-hormones, and enzymes Characteristics of Enzymes Proteins that are biological catalysts Chemically specific Usually named for the reaction they catalyze Names often end in suffix -ase Protein Function - Enzymes Protein and substrate fit together in a specific way due to Hbonds, ionic bonds and non-polar interactions Figure 2.18a Mechanism of Enzyme Action Active site Substrates 1 Enzyme (E) Substrates (s) H20 Enzymesubstrate complex (E–S) 2 Free enzyme (E) 3 Covalent bond Internal rearrangements leading to catalysis Product (P) Nucleic Acids Polymers of nucleotides Nucleotide is N-containing base pentose sugar phosphate group DNA and RNA Nucleotides – The Bases Nucleotides – The Sugars for RNA for DNA Nucleosides – Sugar + Base Deoxyadenosine Nucleotide – Nucleoside + Phosphates Nucleic Acids – Polymers of Nucleotides Structure of DNA Complementary base-pairing A-T G-C Figure 2.21a Deoxyribonucleic Acid (DNA) Double-stranded helical molecule Constitutes chromosomes in nucleus Replicates ensuring genetic continuity Provides instructions for protein synthesis Ribonucleic Acid (RNA) Contains the base uracil in place of thymine Made from a DNA template Three major varieties of RNA: mRNA – encodes a protein tRNA – conveys amino acid to ribosome as directed by mRNA rRNA – joins amino acids together to form protein as directed by mRNA Adenosine Triphosphate (ATP) Source of immediately usable energy for the cell Figure 2.22 How ATP Drives Cellular Work Figure 2.23