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Chapter 2 Lecture Outline

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1 Chapter 2 Lecture Outline
See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 The Chemistry of Life Atoms, Ions and Molecules Water and Mixtures
Energy and Chemical Reactions Organic compounds

3 Atoms, Ions and Molecules
The chemical elements Atomic structure Isotopes and radioactivity Ions, electrolytes and free radicals Molecules and chemical bonds

4 The Chemical Elements Element = simplest form of matter with unique chemical properties Atomic number = # of protons in nucleus periodic table elements arranged by atomic number 24 elements have biological role 6 elements = 98.5% of body weight trace elements in minute amounts

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6 Minerals Inorganic elements absorbed from soil by plants
Equals 40% of body weight structure (teeth, bones, etc) enzymes

7 Structure of an Atom Nucleus = center of atom
protons: single + charge, mass = 1 amu neutrons: no charge, mass = 1 amu Electron shells surround the nucleus electrons: single negative charge, little mass valence electrons in the outermost shell interact with other atoms determine chemical behavior

8 Planetary Models of Elements
p+ represents protons, no represents neutrons

9 Isotopes and Radioactivity
differ in # of neutrons extra neutrons increase atomic weight isotopes of an element are chemically similar have same valence electrons Atomic weight average atomic mass of the isotopes

10 Radioisotopes and Radioactivity
same chemical behavior, differ in physical behavior breakdown gives off radiation Radioisotopes unstable isotopes every element has at least one radioisotope Radioactivity radioisotopes decay to stable isotopes releasing radiation we are all mildly radioactive

11 Marie Curie First woman in world to receive a Ph.D.
First woman to receive Nobel Prize (1903) discovered radioactivity of radium trained physicians in use of X rays and radiation therapy as cancer treatment Died of radiation poisoning at 67

12 Ionizing Radiation Radiation ejects electrons forming ions
Destroys molecules and produces free radicals sources include: UV light, X rays, nuclear decay (, , )  particle (dangerous if inside the body) 2 protons + 2 neutrons can’t penetrate skin  particle (dangerous if inside the body) free electron - penetrates skin a few millimeters  particle (emitted from uranium and plutonium) penetrating; very dangerous gamma rays

13 Ionizing Radiation 2 Physical half-life of radioisotopes
time needed for 50% to decay nuclear power plants create radioisotopes Biological half-life of radioisotopes time for 50% to disappear from the body decay and physiological clearance Radiation exposure in sieverts (Sv) background radiation = radon gas and cosmic rays sources = X rays and radiation therapy

14 Ions and Ionization Ions - carry a charge due to an unequal number of protons and electrons Ionization = transfer of electrons from one atom to another ( stability of valence shell)

15 Anions and Cations Anion Cation
atom that gained electrons (net negative charge) Cation atom that lost an electron (net positive charge) Ions with opposite charges are attracted to each other

16 Electrolytes Salts that ionize in water to form body fluids
capable of conducting electricity Electrolyte importance chemical reactivity osmotic effects (influence water movement) electrical effects on nerve and muscle tissue Imbalances cause muscle cramps, brittle bones, coma and death

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18 Free Radicals Particle with an odd number of electrons Produced by
normal metabolic reactions, radiation, chemicals Causes tissue damage reactions that destroy molecules causes cancer, death of heart tissue and aging Antioxidants neutralize free radicals in diet (vitamin E, carotenoids, vitamin C)

19 Molecules and Chemical Bonds
two or more atoms covalently bonded Compounds two or more atoms of different elements covalently bonded Molecular formula elements and how many atoms of each Structural formula location of each atom structural isomers revealed

20 Structural Formula of Isomers
Molecular formulae are identical, but structural formulas differ for grain alcohol and ether

21 Molecular Weight MW of compound = sum of atomic weights of atoms
Calculate: MW of glucose (C6H12O6) 6 C atoms x 12 amu each = 72 amu 12 H atoms x 1 amu each = 12 amu 6 O atoms x 16 amu each = 96 amu Molecular weight (MW) = 180 amu

22 Chemical Bonds Ionic bonds Covalent bonds Hydrogen bonds
Van der Waals force

23 Ionic Bonds Attraction of oppositely charged ions
No sharing of electrons Weak bond (easily dissociates in water)

24 Covalent Bonds Formed by sharing of valence electrons
Types of covalent bonds single = sharing of single pair electrons double = sharing of 2 pairs nonpolar shared electrons (equal time around each nucleus) strongest of all bonds polar negative charge where electrons spend most time

25 Single Covalent Bond One pair of electrons are shared

26 Double covalent bonds: Two pairs of electrons are shared each C=O bond

27 Nonpolar /Polar Covalent Bonds
electrons shared equally electrons shared unequally

28 Hydrogen Bonds Weakest bond = no sharing of electrons
Attraction between polar molecules positive hydrogen atoms to negative oxygen atoms in a 2nd molecule Physiological importance properties of water created by shapes of large complex molecules determined by folding due to hydrogen bonds

29 Hydrogen Bonding in Water

30 Van der Waals Forces Weak attractions between neutral atoms
Fluctuations in electron density create polarity Only 1% as strong as a covalent bond folding of large molecules significant when 2 large surfaces meet

31 Mixtures and Water Substances physically but not chemically combined
Mixtures in our bodies contain water Water 50-75% of body weight depends on age, sex, percentage body fat, etc.

32 Solvency Solvency - ability to dissolve other chemicals
Hydrophilic (charged substances) dissolve easily in water Hydrophobic (neutral substances) do not easily dissolve in water Water = universal solvent metabolic reactions and transport of substances

33 Water as a Solvent Polar water molecules overpower the ionic bond in Na+Cl- forming hydration spheres around each ion water molecules: negative pole faces Na+, positive pole faces Cl-

34 Adhesion and Cohesion Adhesion – tendency of one substance to cling to another Cohesion – tendency of like molecules to cling to each other water is very cohesive due to its hydrogen bonds surface film on water formed by surface tension

35 Chemical Reactivity of Water
Participation in chemical reactions water ionizes into H+ and OH- water ionizes other chemicals (acids and salts) water involved in hydrolysis and dehydration synthesis reactions

36 Thermal Stability of Water
Water stabilizes internal temperature has high heat capacity hydrogen bonds inhibit temperature increases by inhibiting molecular motion water absorbs heat without changing temperature effective coolant 1 ml of perspiration removes 500 calories calorie: amount of heat required to raise temperature of 1g of water by 1°C

37 Solutions Mixture of a solute into a solvent Small solute particles
pass through cell membranes Solution transparent Remains mixed

38 Colloids Mixture of protein and water
change from liquid to gel state within and between cells Particles too large to pass through cell membranes Cloudy Remains mixed

39 Suspensions and Emulsions
particles suspended in a solvent particles exceed 100nm too large to pass through a cell membrane cloudy or opaque appearance separates on standing Emulsion suspension of one liquid in another fat in breast milk

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41 Measures of Concentration
Weight per Volume weight of solute in given volume of solution IV saline: 8.5 grams NaCl/liter of solution Percentages Weight/volume of solute in solution IV D5W (5% w/v dextrose in distilled water) 5 grams of dextrose and fill to 100 ml water Molarity moles of solute/liter in solution physiologic effects based on number of molecules in solution not on weight

42 Molarity Molecular weight in grams = 1 mole of molecules
1 mole = Avogadro’s number of molecules Molarity is the number of moles of solute/ liter of solution MW of glucose is 180 one-molar (1.0M) glucose solution contains 180g/L

43 Percentage vs. Molar Concentrations
# of molecules unequal weight of solute equal Molar # of molecules equal weight of solute unequal

44 Electrolyte Concentrations
Effect the body chemically, physically and electrically depends on charge and concentration Measured in equivalents 1 Eq will electrically neutralize 1 mole of H+ or OH- ions multiply molar concentration x valence of the ion 1 M Na+ = 1 Eq/L 1 M Ca2+ = 2 Eq/L

45 Acids, Bases and pH An acid is proton donor (releases H+ ions)
A base is proton acceptor (accepts H+ ions) pH = the concentration of H+ ions in solution a pH of less than 7 is acidic solution a pH of greater than 7 is basic solution a pH of 7.0 is neutral pH

46 pH pH = measurement of molarity of H+ [H+] on a logarithmic scale
pH = -log [H+] thus pH = - log [10-3] = 3 a change of one number on the pH scale represents a 10 fold change in H+ concentration a solution with pH of 4.0 is 10 times as acidic as one with pH of 5.0 Our body uses buffers to prevent change pH of blood ranges from 7.35 to 7.45 tremors, paralysis or even death

47 pH Scale

48 Work and Energy Energy - capacity to do work
Kinetic energy - energy of motion heat is kinetic energy of molecular motion Potential energy- energy due to object’s position (ions on one side only of cell membrane) chemical energy - potential energy stored in the molecular bonds

49 Chemical Reaction Process that forms or breaks an ionic or covalent bond Symbolized by chemical equation reactants  products Classes of reactions Decomposition reactions Synthesis reactions Exchange reactions

50 Decomposition Reactions
Large molecules broken down into smaller ones AB  A + B

51 Synthesis Reactions Two or more small molecules combine to form a larger one A + B  AB

52 Exchange Reactions Two molecules collide and exchange atoms or group of atoms AB+CD  ABCD  AC + BD Stomach acid (HCl) and sodium bicarbonate (NaHCO3) from the pancreas combine to form NaCl and H2CO3.

53 Reversible Reactions Go in either direction (symbolized with double-headed arrow) CO2 + H2O H2CO HCO3- + H+ most common equation discussed in this book Law of mass action determines direction side of equation with greater quantity of reactants dominates

54 Reaction Rates Basis for reactions is molecular motion and collisions
reactions occur when molecules collide with enough force and the correct orientation Reaction Rates affected by: concentration more concentrated, more collisions, faster rate temperature higher temperature, greater collision force, faster rate Catalysts (enzymes) speed up reactions without permanent change to itself holds reactant molecules in correct orientation

55 Metabolism All the chemical reactions of the body Catabolism Anabolism
energy releasing (exergonic) decomposition reactions breaks covalent bonds, produces smaller molecules, releases useful energy Anabolism energy storing (endergonic) synthesis reactions requires energy input

56 Oxidation-Reduction Reactions
molecule gives up electrons and releases energy accepting molecule is the oxidizing agent oxygen is often the electron acceptor Reduction molecule gains electrons and energy donating molecule is the reducing agent Oxidation-reduction (redox) reactions Electrons are often transferred as hydrogen atoms

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58 Organic Chemistry Study of compounds containing carbon
4 categories of carbon compounds carbohydrates lipids proteins nucleotides and nucleic acids

59 Organic Molecules and Carbon
Only 4 valence electrons bonds readily to gain more valence electrons Forms long chains, branched molecules and rings serve as the backbone for organic molecules Carries a variety of functional groups

60 Functional Groups Atoms attached to carbon backbone
Determines chemical properties

61 Monomers and Polymers Macromolecules = very large molecules
Polymers = macromolecules formed from monomers bonded together Monomers = an identical or similar subunit

62 Polymerization Bonding of monomers together to form a polymer
Formed by dehydration synthesis starch molecules are a polymer of 3000 glucose monomers protein molecules are a polymer of amino acids

63 Dehydration Synthesis
Monomers covalently bond together to form a polymer with the removal of a water molecule A hydroxyl group is removed from one monomer and a hydrogen from the next

64 Hydrolysis Splitting a polymer (lysis) by the addition of a water molecule (hydro) a covalent bond is broken All digestion reactions consists of hydrolysis reactions

65 Organic Molecules: Carbohydrates
Hydrophilic organic molecule General formula (CH2O)n n = number of carbon atoms for glucose, n = 6, so formula is C6H12O6 2:1 ratio of hydrogen to oxygen Names of carbohydrates word root sacchar- or the suffix -ose often used monosaccharide or glucose

66 Monosaccharides Major monosaccharides Simple sugars
General formula is C6H12O6 structural isomers Major monosaccharides glucose, galactose and fructose produced by digestion of complex carbohydrates glucose is blood sugar

67 Disaccharides Sugar molecule composed of 2 monosaccharides
Major disaccharides sucrose = table sugar glucose + fructose Lactose = sugar in milk glucose + galactose Maltose = grain products glucose + glucose

68 Polysaccharides Chains of glucose subunits
Starch: energy storage in plants digestible by humans for energy Cellulose: structural molecule of plant cell walls fiber in our diet Glycogen: energy storage in animals liver synthesizes after a meal and breaks down between meals

69 Carbohydrate Functions
All digested carbohydrates converted to glucose and oxidized to make ATP Conjugated carbohydrate = bound to lipid or protein glycolipids external surface of cell membrane glycoproteins mucus of respiratory and digestive tracts proteoglycans gels that hold cells and tissues together joint lubrication rubbery texture of cartilage

70

71 Organic Molecules: Lipids
Hydrophobic organic molecule composed of carbon, hydrogen and oxygen Less oxidized and thus has more calories/gram Five primary types in humans fatty acids triglycerides phospholipids eicosanoids steroids

72 Fatty Acids Chain of 4 to 24 carbon atoms Classified
carboxyl (acid) group on one end, methyl group on the other and hydrogen bonded along the sides Classified saturated - carbon atoms saturated with hydrogen unsaturated - contains C=C bonds without hydrogen

73 Triglycerides (Neutral Fats)
3 fatty acids bonded to glycerol molecule (dehydration synthesis) At room temperature when liquid called oils often polyunsaturated fats from plants when solid called fat saturated fats from animals Function - energy storage, insulation and shock absorption

74 Phospholipids Triglyceride with one fatty acid replaced by a phosphate group Amphiphilic character fatty acid “tails” are hydrophobic Phosphate “head” is hydrophilic

75 Eicosanoids Derived from arachidonic acid (a fatty acid)
Hormone-like chemical signals between cells Includes prostaglandins – produced in all tissues role in inflammation, blood clotting, hormone action, labor contractions, blood vessel diameter

76 Steroids and Cholesterol
Steroid = lipid with carbon atoms in four rings all steroids are derived from cholesterol cortisol, progesterone, estrogens, testosterone and bile acids Cholesterol important component of cell membranes produced only in animal liver cells naturally produced by our body

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78 Organic Molecules: Proteins
Protein = polymer of amino acids Combination determines structure and function Amino acid = carbon with 3 attachments Amino (NH2), carboxy (COOH) and radical group (R group) 20 unique amino acids -R groups differ properties determined by -R group

79 Naming of Peptides Peptide = polymer of 2 or more amino acids
Named for the number of amino acids dipeptides have 2, tripeptides have 3 oligopeptides have fewer than 10 to 15 polypeptides have more than 15 proteins have more than 100

80 Dipeptide Synthesis Dehydration synthesis creates a peptide bond that joins amino acids

81 Protein Structure and Shape
Primary structure amino acid sequence Secondary structure coiled or folded shape hydrogen bonds between negative C=O and positive N-H groups Tertiary structure further folding and bending into globular and fibrous shapes Quaternary structure associations of two or more separate polypeptide chains

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83 Conjugated Proteins Contain a non-amino acid moiety
Hemoglobin contains complex iron containing ring called a heme moiety

84 Protein Conformation and Denaturation
Conformation – unique 3-D shape crucial to function ability to reversibly change their conformation opening and closing of cell membrane pores Denaturation conformational change that destroys function extreme heat or pH

85 Protein Functions Structure Communication Membrane Transport Catalysis
collagen, keratin Communication some hormones, cell receptors Membrane Transport channels, carriers Catalysis enzymes

86 Protein Functions 2 Recognition and protection Movement Cell adhesion
antigens, antibodies and clotting proteins Movement molecular motor = molecules that can change shape repeatedly Cell adhesion proteins bind cells together

87 Enzymes Proteins as biological catalysts
promote rapid reaction rates Substrate - substance an enzyme acts upon Naming Convention named for substrate with -ase as the suffix amylase enzyme digests starch (amylose) Lowers activation energy = energy needed to get reaction started enzymes facilitate molecular interaction

88 Enzymes and Activation Energy

89 Steps of an Enzyme Reaction
Substrate approaches enzyme molecule Substrate binds to active site forming enzyme-substrate complex highly specific Enzyme breaks bonds in substrate Reaction products released Enzyme repeats process over and over

90 Enzymatic Reaction Steps

91 Enzymatic Action Reusability of enzymes Astonishing speed
enzymes are unchanged by the reactions Astonishing speed millions of molecules per minute Temperature and pH change shape of enzyme and alter its ability to bind enzymes vary in optimum pH salivary amylase works best at pH 7.0 pepsin works best at pH 2.0 temperature optimum for human enzymes = body temperature

92 Cofactors and Coenzymes
nonprotein partners (iron, copper, zinc, magnesium or calcium ions) bind to enzyme and change its shape essential to function Coenzymes organic cofactors derived from water-soluble vitamins (niacin, riboflavin) transfer electrons between enzymes

93 Coenzyme NAD+ NAD+ transports electrons from one metabolic pathway to another

94 Metabolic Pathways Chain of reactions, each catalyzed by an enzyme
   A  B  C  D A is initial reactant, B+C are intermediates and D is the end product Regulation of metabolic pathways activation or deactivation of the enzymes cells can turn on or off pathways

95 Organic Molecules: Nucleotides
3 components nitrogenous base sugar (monosaccharide) one or more phosphate groups Physiological important nucleotides ATP = energy carrying molecule cAMP = activates metabolic pathways DNA = carries genetic code RNA = assists with protein synthesis

96 ATP (Adenosine Triphosphate)
ATP contains adenine, ribose and 3 phosphate groups

97 ATP Holds energy in covalent bonds
2nd and 3rd phosphate groups have high energy bonds ~ ATPases hydrolyze the 3rd high energy phosphate bond separates into ADP + Pi + energy Phosphorylation addition of free phosphate group to another molecule

98 Overview of ATP Production
ATP consumed within 60 seconds Continually replenished

99 Other Nucleotides Cyclic adenosine monophosphate (cAMP)
formed by removal of both high energy Pi’s from ATP formation triggered by hormone binding to cell surface cAMP becomes “second messenger” within cell activates effects inside cell

100 Nucleic Acids DNA (deoxyribonucleic acid)
100 million to 1 billion nucleotides long contains genetic code cell division, sexual reproduction, protein synthesis RNA (ribonucleic acid) – 3 types transfer RNA, messenger RNA, ribosomal RNA 70 to 10,000 nucleotides long involved in protein synthesis coded for by DNA


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