1. Chapter 2 Chemistry

2. Major Elements of the Human Body Oxygen (O) Carbon (C) Hydrogen (H) Nitrogen (N)

3. Lesser and Trace Elements of the Human Body Lesser elements make up 3.9% of the body and include: –Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), iodine (I), and iron (Fe)

4. Atomic Structure The nucleus consists of neutrons and protons –Neutrons – have no charge and a mass of one atomic mass unit (amu) –Protons – have a positive charge and a mass of 1 amu Electrons are found orbiting the nucleus –Electrons – have a negative charge and 1/2000 the mass of a proton (0 amu)

5. Identification of Elements Atomic number – equal to the number of protons Mass number – equal to the mass of the protons and neutrons Atomic weight – average of the mass numbers of all isotopes

6. Identification of Elements Isotope – atoms with same number of protons but a different number of neutrons Radioisotopes – atoms that undergo spontaneous decay called radioactivity

7. Molecules and Compounds Molecule – two or more atoms held together by chemical bonds Compound – two or more different kinds of atoms chemically bonded together

8. Mixtures and Solutions Mixtures – two or more components physically intermixed (not chemically bonded) Solutions – homogeneous mixtures of components –Solvent – substance present in greatest amount –Solute – substance(s) present in smaller amounts

9. Concentration of Solutions Percent, or parts per 100 parts Molarity, or moles per liter (M) A mole of an element or compound is equal to its atomic or molecular weight (sum of atomic weights) in grams

10. Colloids and Suspensions Colloids (emulsions) – heterogeneous mixtures whose solutes do not settle out Suspensions – heterogeneous mixtures with visible solutes that tend to settle out

11. Mixtures Compared with Compounds No chemical bonding takes place in mixtures Most mixtures can be separated by physical means Mixtures can be heterogeneous or homogeneous Compounds cannot be separated by physical means All compounds are homogeneous

12. Types of Chemical Bonds Ionic Covalent Hydrogen

13. Ionic Bonds Ions are charged atoms resulting from the gain or loss of electrons Anions have gained one or more electrons Cations have lost one or more electrons

14. Formation of an Ionic Bond Ionic bonds form between atoms by the transfer of one or more electrons Ionic compounds form crystals instead of individual molecules Example: NaCl (sodium chloride)

15. Formation of an Ionic Bond Figure 2.5a

16. Covalent Bonds Covalent bonds are formed by the sharing of two or more electrons Electron sharing produces molecules

17. Single Covalent Bonds Figure 2.7a

18. Polar and Nonpolar Molecules Electrons shared equally between atoms produce nonpolar molecules Unequal sharing of electrons produces polar molecules Atoms with six or seven valence shell electrons are electronegative Atoms with one or two valence shell electrons are electropositive

19. Comparison of Ionic, Polar Covalent, and Nonpolar Covalent Bonds Figure 2.9

20. Hydrogen Bonds Too weak to bind atoms together Common in dipoles such as water Responsible for surface tension in water Important as intramolecular bonds, giving the molecule a three-dimensional shape

21. Hydrogen Bonds Figure 2.10a

22. Oxidation-Reduction (Redox) Reactions Reactants losing electrons are electron donors and are oxidized Reactants taking up electrons are electron acceptors and become reduced

23. Factors Influencing Rate of Chemical Reactions Temperature – chemical reactions proceed quicker at higher temperatures Particle size – the smaller the particle the faster the chemical reaction Concentration – higher reacting particle concentrations produce faster reactions Catalysts – increase the rate of a reaction without being chemically changed Enzymes – biological catalysts

24. 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

25. 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 Reactivity – is an important part of hydrolysis and dehydration synthesis reactions Cushioning – resilient cushion around certain body organs

26. Salts Inorganic compounds Contain cations other than H + and anions other than OH – Are electrolytes; they conduct electrical currents

27. Acids and Bases Acids release H + and are therefore proton donors HCl  H + + Cl – Bases release OH – and are proton acceptors NaOH  Na + + OH –

28. 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

29. Acid-Base Concentration (pH) Acidic: pH 0–6.99 Basic: pH 7.01–14 Neutral: pH 7.00 Figure 2.13

30. Buffers Systems that resist abrupt and large swings in the pH of body fluids Carbonic acid-bicarbonate system –Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons –The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood

31. Organic Compounds Molecules unique to living systems contain carbon and hence are organic compounds They include: –Carbohydrates –Lipids –Proteins –Nucleic Acids

32. 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

33. Carbohydrates Disaccharides or double sugars Figure 2.14b

34. Carbohydrates Polysaccharides or polymers of simple sugars Figure 2.14c

35. Lipids Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates Examples: –Neutral fats or triglycerides –Phospholipids –Steroids –Eicosanoids

36. Neutral Fats (Triglycerides) Composed of three fatty acids bonded to a glycerol molecule Figure 2.15a

37. Other Lipids Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group Figure 2.15b

38. Other Lipids Steroids – flat molecules with four interlocking hydrocarbon rings Eicosanoids – 20-carbon fatty acids found in cell membranes Figure 2.15c

39. 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 Fat-soluble vitamins – vitamins A, E, and K Eicosanoids – prostaglandins, leukotrienes, and thromboxanes Lipoproteins – transport fatty acids and cholesterol in the bloodstream

40. Amino Acids Building blocks of protein, containing an amino group and a carboxyl group Amino group NH 2 Carboxyl groups COOH

41. Protein Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Figure 2.17 Amino acid Dehydration synthesis Hydrolysis Dipeptide Peptide bond +N H H C R H O N H H C R CC H O H2OH2O H2OH2O N H H C R C H O N H C R C H O OH

42. Structural Levels of Proteins Primary – amino acid sequence Secondary – alpha helices or beta pleated sheets Tertiary – superimposed folding of secondary structures Quaternary – polypeptide chains linked together in a specific manner

43. Structural Levels of Proteins Figure 2.18a–c

44. Structural Levels of Proteins Figure 2.18b,d,e

45. Fibrous and Globular Proteins Fibrous proteins –Extended and strand-like proteins –Examples: keratin, elastin, collagen, and certain contractile fibers Globular proteins –Compact, spherical proteins with tertiary and quaternary structures –Examples: antibodies, hormones, and enzymes

46. Protein Denuaturation Reversible unfolding of proteins due to drops in pH and/or increased temperature Figure 2.19a

47. Protein Denuaturation Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes Figure 2.19b

48. 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

49. 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 Frequently named for the type of reaction they catalyze Enzyme names usually end in -ase Lower activation energy

50. Characteristics of Enzymes Figure 2.20

51. Mechanism of Enzyme Action Enzyme binds with substrate Product is formed at a lower activation energy Product is released Active site Amino acids Enzyme (E) Enzyme-substrate complex (E-S) Internal rearrangements leading to catalysis Dipeptide product (P) Free enzyme (E) Substrates (S) Peptide bond H2OH2O +

52. 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 Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) Two major classes – DNA and RNA

53. 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

54. Structure of DNA Figure 2.22a

55. Structure of DNA Figure 2.22b

56. 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

57. Adenosine Triphosphate (ATP) Source of immediately usable energy for the cell Adenine-containing RNA nucleotide with three phosphate groups

58. Adenosine Triphosphate (ATP) Figure 2.23