Chemistry Comes Alive

2. 2 P A R T A Chemistry Comes Alive

3. Figure 2.11: Patterns of chemical reactions, p. 38. Amino acids Protein molecule (a) Example of a synthesis reaction:amino acids are joined to form a protein molecule Glycogen Glucose molecules (b) Example of a decomposition reaction: breakdown of glycogen to release glucose units O + O P P P Glucose Adenosine triphosphate (ATP) P O + O P P Glucose phosphate Adenosine diphosphate (ADP) (c) Example of an exchange reaction: ATP transfers its terminal phosphate group to glucose to form glucose-phosphate

4. Factors Influencing Rate of Chemical Reactions • Chemicals react when they collide with enough force to overcome the repulsion by their electrons • 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

5. Energy Flow in Chemical Reactions • Exergonic reactions – reactions that release energy • Endergonic reactions – reactions whose products contain more potential energy than did its reactants

6. Biochemistry - study of the chemistry of living things • Organic compounds • Contain carbon, are covalently bonded, and are often large • Inorganic compounds • Do not contain carbon • Water, salts, and many acids and bases

7. Properties of Water • Water is the most important inorganic molecule, and makes up 60–80% of the volume of most living cells • 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

8. Salts • Inorganic compounds • Contain cations other than H+ and anions other than OH– • When salts are dissolved in water they dissociate into their component ions • Are electrolytes; they conduct electrical currents

9. Figure 2.12: Dissociation of a salt in water, p. 40. Ions in solution Salt crystal Na+ Na+ Cl– Cl– + H Water molecule O + – H

10. Acids and Bases • Acid – molecule that can release protons (H+) into a solution; proton donor; pH= less than 7 HCl  H+ + Cl – • Base - molecule that can release OH- (hydroxyl ions) into a solution which may combine with H+ to form water; lowers H+ concentration; proton acceptor; pH = greater than 7 NaOH  Na+ + OH–

11. 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 • Water molecules will occasionally break apart (ionize) leaving the hydrogen electron attached to the oxygen atom • Ionization of water produces equal amounts of H+ and OH- • Neutralization occurs when an acid and a base are mixed together. They react with each other in displacement reactions to form a salt and water.

12. pH scale • Based on the number of hydrogen ions (H+) in solution • pH scale runs from 0 to 14; each successive change of 1 pH unit represents a 10-fold change in hydrogen ion concentration • pH = -log10[H+] , where [H+] = molar conc. • Pure water = [H+] = 10-7M; therefore it has a pH of 7; neutral; [H+] = [OH-] • If [H+] is greater than [OH-], solution is acid • If [OH-] is greater that [H+], solution is base

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

14. Buffers • system of molecules and ions that acts to prevent drastic changes in H+ concentration; stabilizes pH of solution • Living cells are extremely sensitive to light changes in pH – must remain between 7.35 and 7.45 • Acid-base balance is regulated by the kidneys, lungs, and buffers found in 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

15. Acidosis – blood pH falls below 7.35; hemoglobin in blood cells cannot carry enough oxygen, hydrogen bonds begin to break in proteins; person may become comatose & die • Alkalosis – increase in blood pH above 7.45; may be life threatening if pH rises above 7.8 for more than a few hours

16. Metabolic Acidosis – excess of any acid except H2CO3 Causes: Excess Acid OR Loss of Base Diabetic ketoacidosis vomiting Starvation ketosis diarrhea Lactic acidosis High K+ (Hyperkalemia)

17. Metabolic Alkalosis Causes: Too Little Acid OR Too Much Base Vomiting Ingesting too much HCO3 Hypokalemia (K+ )

18. Respiratory Acidosis – excess CO2 Causes: • Impaired gas exchange • Impaired activity of diaphragm muscle • Impaired respiratory control in brain stem • emphysema

19. Respiratory Alkalosis – deficit of CO2 Causes – Hyperventilation 1. low levels of O2 in plasma 2. Meningitis – stimulation of brain stem 3. Head injury 4. severe anxiety Symptoms: • Sweating, numbness, tingling, dizziness, confusion, • Cerebral vasal constriction – seizures, coma

20. Controlling Body pH • Chemical Buffers • Acts within seconds but with limited capacity • Respiratory Control • Acts within minutes • Compensates for metabolic acidosis & alkalosis • Renal Mechanisms • Acts in hours or days • Compensates for respiratory acidosis & alkalosis

21. CompensationEquation CO2 + H2O H2CO3 HCO3 + H (carbonic acid) (carbonate)

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

23. Carbohydrates - class of molecules ranging from small sugar molecules to large polysaccharides • Organic molecules unique to living systems that contain carbon, hydrogen, and oxygen in the ratio described by their name - carbo (carbon) and hydrate (H2O) = CH2O • Their major function is to supply a source of cellular food May be divided into three groups by size 1) monosaccharides - simplest; monomer, contains one sugar molecule; many form ring-shaped molecules in solution

24. Many are structural isomers of each other – glucose, galactose, and fructose have the same molecular formula, but different structural arrangements. • Glucose = blood sugar, universal cellular fuel • Ribose & deoxyribose – part of RNA and DNA

25. Pharmaceutical companies must understand and appropriately deal with isomers • Isomers – same chemical formula but different structural arrangements of the atoms • Enantiomers – isomers which are mirror images of each other; L (levo-) and D (dextro) - cells and tissues will typically respond to only one structural form – L or D - but not both - our cells can only metabolize L-glucose as an energy source although both forms are present • http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/083_Chirality.MOV

26. Chloramphenicol – antibiotic which contains both L- and D- isomers; only L- form is effective in killing bacterial pathogens • Ephedrine – bronchiolar dilator used for asthma patients; L- form is active, D- form is inactive • Thalidomide – both L- and D- forms are biologically active but in different ways - drug given to expectant women for severe nausea - medication contained both forms; one stopped nausea, one caused abnormalities in fetal limb development

27. 2) disaccharides - composed of two monosaccharides by dehydration synthesis in the cells; ex: glucose + fructose = sucrose - sucrose = glucose-fructose = cane sugar - lactose = glucose-galactose = milk sugar - maltose – glucose-glucose = malt sugar • Double sugar are too large to pass through cell membranes, they must be digested (broken down by hydrolysis) to monosaccharides to be absorbed from the digestive tract into the blood

28. Disaccharides or double sugars Disaccharides Figure 2.14b

29. dehydration synthesis - molecules synthesized by loss of a water molecule between reacting monomers; most common way to synthesize organic polymers

30. Hydrolysis - “breaking apart with water”; the way most organic polymers are degraded

31. Carbohydrates 3) polysaccharides - long chains of sugar units; glucose is the monomer for many polysacchaarides - considered to be ideal storage molecules because they are not soluble in water • Starch and glycogen are the two polysaccharides of importance in the body - starch - found in plants for long-term energy storage; long, unbranched, helical polymer of covalently bonded glucose monomers; may be ingested as “starchy” foods such as grain products and root vegetables Figure 2.14c

32. glycogen - similar to starch but is slightly smaller and has more side branches; used for long-term storage in the muscles and liver of animals - liver and muscles store excess glucose from the blood in the form of glycogen; during fasting or prolonged exercise, the liver adds glucose to the blood through hydrolysis of stored glycogen

33. Highly branched glycogen

34. Lipids - diverse nonpolar compounds consisting mainly of carbon and hydrogen (few oxygen); hydrophobic • Lipids are insoluble in water but dissolve readily in nonpolar solvents • Most abundant and concentrated source of usable energy • Enter the body in the form of fat-marbled meats, egg yolks, milk products, and oils • Stored in fat deposits beneath the skin and around body organs; may help to insulate the body and protect deeper body tissues from heat loss and bumps

35. Lipids • Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates • Examples: • Neutral fats or triglycerides - known as fats when solid and oils when liquid • Phospholipids - diglycerides with a phosphorus-containing group and two fatty acid chainsSteroids • Steroids - flat molecules made up of four interlocking hydrocarbon rings • Eicosanoids - group of diverse lipids derived from arachidonic acid

36. The three most abundant lipids in the body are triglycerides, phospholipids, and steroids • Neutral Fats (Triglycerides) - energy storage molecules; most are hydrophobic; contain 3 fatty acids and 1 glycerol – found in subcutaneous tissue and around organs Figure 2.15a

37. - saturated fats - no double bonds between carbons (carbons are “saturated” with hydrogen atoms); backbones are flexible and tend to ball up into tight globules; solid at room temperature; lead to atherosclerotic plaques - unsaturated fats - many double bonds between carbons; causes molecules to be less flexible; do not pack into solid globules; most are liquid at room temperature -Trans-fatty acids have straightened double bonds and thus act like saturated fat.

38. Saturated and Unsaturated triglycerides

39. health authorities recommend that total fat intake not exceed 30% of the total energy intake per day and that saturated fat contribute less than 10% of that total

40. 2) phospholipids - major component of cell membranes; 1 glycerol + 2 fatty acids + 1 phosphate group; hydrophobic “tail” and hydrophilic “head” Figure 2.15b

41. - important physiological functions include their role as the major component of the cell membrane which allows the cell to be selective about what may enter or leave, and their ability to decrease surface tension of water (surfactant – surface –active agent) – important in preventing the collapse of the lungs

42. 3) steroids – flat lipids with backbones bent into rings - cholesterol is a steroid formed by animals & functions in the digestion of fats and in the synthesis of hormones produced by the testes, ovaries, and adrenal cortex - testes and ovaries (gonads) secrete sex steroids - ovaries produce progesterone and estradiol - testes produce testosterone - adrenal cortex produces corticosteroids • Other Steroids include – bile salts, vitamin D

43. anabolic steroids - synthetic steroids which resemble & mimic the male hormone testosterone; causes buildup of muscle and bone mass, bloating of face, violent mood swings, deep depressions, liver damage leading to cancer, reduced sex drive, cardiovascular problems, infertility due to reduced output of natural sex hormones, etc.

44. Example of Anabolic Steroid Use Tetrahydrogestrinone (THG) For a time, THG was considered the drug of choice for safe and "invisible" world record breaking in athletics, being used by several high profile gold medal winners such as the sprinter Marion Jones, who resigned from her athletic career in 2007 after admitting to using THG prior to the 2000 Sydney Olympics, where she had won three gold medals Marion Jones

45. Comparison of Cholesterol to Hormones

46. Other Lipids Table 2.2.2

47. Proteins – very large biological polymer constructed from amino acid monomers • Account for over 50% of the organic matter in the body, and have the most varied functions - structural (cytoskeleton, hair, collagen) - contractile (muscle) - storage (egg whites store AA) - defense (antibodies, membranes) - signaling (hormones) - catalyst (enzymes) - receptors (for hormones) - carriers (transport across membranes)

48. Proteins - made from 20 kinds of amino acids • The 20 different amino acids each have their own particular properties • amino acids are characterized by each having an alpha (central) carbon atom covalently bonded to one hydrogen, one amino group, one carboxyl group, and one other chemical group (R group) • Differences in the R group makes each amino acid unique

49. Amino Acids Figure 2.16a–c

50. Amino Acids Figure 2.16d, e