Chemistry of Life. Chapter Two

Transcription

1 Chemistry of Life Chapter Two 1

2 Biology and Chemistry Biology = study of life Chemistry = study of matter and the changes it undergoes Matter anything that takes up space and has mass Life is made up of atoms 2

3 2.1 Atoms, Ions, and Molecules Atoms Building blocks of matter Tiny Models Help explain structure and properties 3

4 Atomic Structure Three subatomic particles: Protons (p + ) Neutrons (n o ) Electrons (e - ) 4

5 Subatomic Particles Protons Same size as n o Inside nucleus Positive charge Same number as e - Identifies element 5

6 Subatomic Particles Neutrons Same size as p+ Inside nucleus No charge Helps hold nucleus together 6

7 Subatomic Particles Electrons Smallest Outside nucleus Negative charge Same number as p+ Involved in chemical reactions 7

8 Atomic Review Nucleus Core of atom Dense p+ and n o e- are outside the nucleus Atoms are neutral Same # of p+ as e- 8

9 Elements Pure; made of just one kind of atom >100 different kinds 91 natural ~25 found in organisms Represented by chemical symbols 9

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11 Elements Differ in # of p+ in atoms Atomic number = # of p+ in atom Ex: Carbon = 6 Oxygen = 8 Hydrogen = 1 What element is shown? 11

12 Elements Atomic Mass sum of p + and n o in an atom atomic weight 12

13 Isotope Atoms of the same element that differ in the # n o Same element Same # p+ Same # e- Different # n o Ex: Hydrogen 13

14 Mystery Atom How many protons? How many electrons? What is the atomic number? What is the name? What is its chemical symbol? 14

15 In Your Own Words: Differentiate between an atom and an element: What is an atom? What is an element? How are they related? 15

16 Compounds Made up of two or more different kinds of atoms joined together represented by chemical formulas Formulas tell type of elements and proportion (# of atoms of each element) Ex: Water = H2O Sodium chloride = NaCl Carbon dioxide = CO2 16

17 Chemical Bonding Atoms join with other atoms to form compounds Force that holds the atoms together = chemical bond 17

18 Chemical Bonds Atomic Glue Three basic types: Ionic bonds Covalent bonds Hydrogen bonds 18

19 Ion An atom that has gained or lost one or more electron Now different # of p+ and e- Not neutral Has a charge! 19

20 Ions Cation an atom that has lost one or more electrons positive charge Anion an atom that has gained one or more electrons negative charge 20

21 Atoms Want Stability 21

22 Ionic Bonding Ex: NaCl = Table Salt Na gives up an e- Becomes cation Cl takes in an e- Becomes anion Opposites attract and BOND 22

23 Ionic Bonding 23

24 Covalent Bonding Atoms share e- to gain stability Fill outer shell with e- 24

25 Covalent Bonds Molecule two or more atoms held together by a covalent bond 25

26 Covalent Molecules Ex: Water Carbon dioxide Oxygen 26

27 2.2 Properties of Water ~70% of your body is water ~2/3 of molecules in your body

28 Hydrogen Bonding Weak bond between polar molecules Holds molecules together Water = good example Often between slightly positive H atom and slightly negative N or O atom Opposite charges attract 28

29 Polar Molecules Overall molecule is neutral e- shared unequally One end positive One end negative Ex: Water 29

30 Hydrogen Bonding in Water 30

31 Water in Living Things Your cells: filled AND surrounded by water All living things need water Properties of water 7 min British 31

32 Properties Related to H bonding 1) Specific heat 2) Cohesion 3) Adhesion 32

33 1)High Specific Heat Water: Heats up slowly Cools down slowly Helps regulate body temperature Evaporation 33

34 2) Cohesion Force of attraction between similar substances Ex: Hydrogen bonding in water Creates surface tension surface doesn t break easily 34

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36 3) Adhesion Attraction between different substances Ex: Water is attracted to other polar substances Adhesion is stronger than cohesion in water molecules Explains water meniscus

37 Adhesion Powers capillary action Water moves upward through tiny tubes against gravity Ex: water moving up a plant 37

38 Aqueous Solutions Solution of a substance dissolved in water Solution - mixture of evenly distributed substances (homogeneous) 38

39 Solution Parts Solvent does the dissolving Solute- gets dissolved Concentration the amount of solute dissolved in solvent

40 Polarity of Water Review: Overall molecule = neutral One end = positive One end = negative Opposites attract 40

41 Like Dissolves Like Water dissolves ionic compounds and polar molecules best Ionic compounds break apart into ions in water Ions have charges 41

42 Sodium Chloride in Water 42

43 Sodium chloride is an example of : 43

44 Oil and Water do NOT mix! Nonpolar and polar do NOT mix Nonpolar substances do not dissolve well in water Important to organisms Nonpolar membranes 44

45 Acid Compound that releases a hydrogen ion (H + ) - when dissolved in water H + is a proton 45

46 Bases Compounds that form hydroxide ions (OH - ) when dissolved in water Reduces concentration of H + OH - react with H + to form H 2 O 46

47 Acids and Bases 47

48 ph Scale Measures concentration of H + in a solution ph scale runs from 0-14 below 7 = acidic above 7 = basic ph equal to 7 is neutral 48

49 ph Scale Each step is a ten fold change in H + concentration! Ex: ph 4 is x more acidic than ph of 6? 49

50 ph of Common Household Items 50

51 ph Range in organisms Very narrow Ex: human blood ph Azalea plant ph 4.5 Buffers help regulate ph binds to H + when too many, and releases H + when not enough

52 Thinker... Cells have a higher concentration of Hydrogen ions than blood. Which has a higher ph blood or a cell? Why?

53 2.3 Carbon Compounds = Organic compound Contain C building block of life Usually forms: 4 covalent bonds Long chains or rings 53

54 Carbon Molecules Monomer subunit of the molecule Polymer Many monomers bonded together large molecule (macromolecule)

55 Classes of Organic Compounds 1) Carbohydrates 2) Lipids 3) Proteins 4) Nucleic Acids 55

56 1) Carbohydrates Made of C, H, and O Often 1:2:1 ratio Most have 5 or 6 C atoms Key energy source Monomer (building block) = monosaccharides 56

57 A) Monosaccharides Simple sugars Mono = one Saccharide = sugar Examples: Glucose Fructose Galactose 57

58 B) Disaccharides Double sugars Di = two Two monosaccharides joined Ex: Sucrose = table sugar glucose + Fructose 58

59 C) Polysaccharides Poly = many Polymers of monosaccharides Macromolecules Macro = big 59

60 Polysaccharides Some store energy Plants = starch Animals = glycogen In plants, they also provide support Ex: Cellulose in cell walls 60

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62 2) Lipids Not soluble in water Nonpolar Examples: Fats Oils Waxes Steroids Cholesterol Phospholipids Cell membranes 62

63 Lipids include Fats Store lots of energy Building blocks: 1) Fatty acids chain of C bonded to H 2) Glycerol Triglyceride = 3 fatty acids + glycerol Many lipids 63

64 Saturated Fatty Acids Lots of C H single bonds Generally solids at room temp Ex: Animal fats Butter Lard Grease 64

65 Unsaturated Fatty Acids Some double bonds Bends molecule Can t pack tightly together to become solid Generally liquids at room temp Most plant oils Some fish oils 65

66 Hydrogenated fats Trans Fats Made when unsaturated fat has H added Becomes more solid More saturated with H Tastes better. Lasts longer. Not good for you! Not natural! 66

67 Phospholipids Make up cell membranes Contain Glycerol 2 fatty acids Nonpolar tails Phosphate group (PO 4- ) Polar head 67

68 Cholesterol Ring structure Too much = not good Necessary for: Cell membrane structure Steroid hormone production Ex: testosterone, estrogen 68

69 3) Proteins Important to life Ex: enzymes Promote chemical reactions Ex: structural proteins Collagen Keratin Fibrin Hemoglobin 69

70 Proteins Large molecules = macromolecules Building blocks = Amino acids (aa) 70

71 Amino Acids Twenty different aa Some polar Some nonpolar Fold into shapes Our body makes 12 Get other 8 from food 71

72 Amino Acids Contain C,H,O,N and sometimes S Most varied organic compound All have: C bonded to H Amino group (NH 2 ) Carboxyl group (COOH) Only differ in R-group (side chain)

73 Examples of aa

74 AA Bonding Form Peptide bonds covalent bonds Linked chains = polypeptides Protein = 1 or more polypeptides

75 Proteins AA sequence determines structure and function Ex: hemoglobin In RBCs One incorrect aa = sickle cell anemia

76 4) Nucleic Acids long chain-like molecule Nucleotides = building blocks (monomer) Store protein making info 76

77 Nucleotides 3 parts Phosphate group Sugar Nitrogen base 77

78 Two kinds 1) DNA Two strands Spiral shape Stores hereditary info makes up chromosomes 78

79 Two kinds of nucleic acids 2) RNA One strand 3 different types Key role in making proteins Can act as enzyme 79

80 ATP Adenosine triphosphate Single nucleotide with 2 extra phosphate groups Energy currency Fuels cell activities 80

81 ATP 81

82 2.4 Chemical Reactions Change substances into different substances by making and breaking bonds Reactants substances changed Products substances made Bond Energy amount of energy needed to break a bond between 2 atoms

83 Energy Ability to move or change matter Many forms: Light Heat Chemical Electrical Mechanical (motion) 83

84 Energy Conversions can change from one form to another Ex: Kicking a ball Frying an egg 84

85 Chemical Reactions Energy stored or released Atoms rearranged 1000s of reactions per cell per second! 85

86 Chemical Reactions Reactants Starting materials Before reaction Products Ending materials After reaction Arrow = yields 86

87 Energy in Chemical Reactions Involve energy changes Bonds are broken and formed Energy is either absorbed or released 87

88 Energy-Releasing Reaction Exothermic Gives off energy Ex: Squid and firefly light Water freezing Cellular respiration 88

89 Energy-Absorbing Reaction Endothermic Takes in energy Ex: Melting of ice Photosynthesis 89

90 Metabolism Sum of all chemical reactions in organism Energy comes from food 90

91 Activation Energy Energy needed to start a chemical reaction Energy absorbed chemical push Amount needed varies Analogy: To get a boulder to roll downhill, First you must push it up 91

92 2.5 Enzymes Act as catalysts Speed up chemical reactions (rxs) in cells Lower activation energy 92

93 Cells and Energy Cells must have fuel Chemical rxs in cells occur: Quickly Low temperatures 93

94 Enzymes Required for Life Help maintain homeostasis w/o enzymes rxs would be too slow Life could not exist 94

95 Carbonic Anhydrase Enzyme in blood Helps convert CO 2 and H 2 O into carbonic acid Carried to lungs Converted back into carbon dioxide and water 95

96 Do not write; just an example Without Carbonic anhydrase Slow rx 2000 molecules per hour converted Not fast enough Millions of cells release CO 2 96

97 Do not write; just an example With enzyme 600,000 molecules per second Increases rate a million times! 97

98 Do not write; just an example Catalase enzyme Helps breakdown hydrogen peroxide (toxic to cells) Reduce activation energy quicker 98

99 Enzyme Specificity Each enzyme acts only on a specific substrate (reactant) Substrate Substance on which an enzyme acts Lock and key model 99

100 Active Sites Shape is everything! Enzymes bend slightly around substrate Active site - site on enzyme where substrate temporarily binds 100

101 Enzymes 101

102 Factors That Affect Enzymes 1)Temperature Operate best within certain range 102

103 Factors That Affect Enzymes 2) ph Operate best within certain range Thinker: If the HCl in the stomach has a ph of ~2, which enzyme on the chart would function best here? 103

104 Enzyme Activity Many different ones Each for different rx Not used up Used over 104