Chemical Bonds Properties of Water Acids and Bases Organic Molecules Enzymes

Transcription

1 Chemical Bonds Properties of Water Acids and Bases Organic Molecules Enzymes 1

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6 Atoms, Ions and Molecules Molecule: 2 or more atoms join together chemically Compound: molecule that contains 2 or more different elements All compounds are molecules but not all molecules are compounds. 6

7 Take Home Message Atoms are the smallest particles of matter that have distinct physical and chemical properties. Each different type of atom makes up an element, which is characterized by an atomic weight and an atomic symbol. The most common elements (found in living things) are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, sodium, chlorine, potassium and calcium (C, H, O, N, P, S, Na, Cl, K, Ca). A molecule is 2 or more atoms join together chemically; a compound is a molecule that contains 2 or more different elements 7

8 Covalent Ionic Polar Covalent Hydrogen 8

9 Covalent Bonds 9

10 Ionic Bonds 10

11 Polar Covalent Bonds electrons shared by the atoms spend a greater amount of time, on average, closer to one nucleus than the other due to geometry of molecule and electronegativity differences result is a charge separation in the molecule, where one part of the molecule has a partial negative charge and one part has a partial positive charge 11

12 Polar Covalent Bonds molecule is not an ion (no excess of protons or electrons) water peptide bonds amines polar covalent bonds can lead to the formation of a hydrogen bond (weak) 12

13 Polar Covalent Bonds 13

14 Hydrogen Bonds weak attractive force between a proton in one molecule and an electronegative atom in a second molecule holds the two strands of a DNA molecule in position hydrogen atom in one nitrogen base is attracted to the negatively charged region of a second nitrogen base water and ammonia because the positively-charged hydrogen atom (proton) in a water molecule is attracted to the free electron pair on the nitrogen atom of the ammonia molecule 14

15 Hydrogen Bonds classified as weak bonds because they are easily and rapidly formed and broken under normal biological conditions molecules that have nonpolar covalent bonds do not form hydrogen bonds 15

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17 Hydrogen Bonds important in biological systems explains many of the properties of water used to stabilize and determine the structure of large macromolecules like proteins and nucleic acids involved in the mechanism of enzyme catalysis 17

18 Bond Strength Ionic Covalent (strongest) Polar Covalent Hydrogen (weakest) 18

19 What characteristic of an atom gives it its chemical properties? 1. the number of protons 2. the number of neutrons 3. the number of electrons 4. the number of electrons in its outer orbital 19

20 Take Home Message From strongest to weakest, the types of bonds that can form between atoms to form molecules are: Covalent electrons are shared Ionic electrons are transferred from one atom to another Polar covalent unequal sharing of electrons Hydrogen - weak attraction between a proton in one molecule and an electronegative atom in a second molecule 20

21 All life on earth depends on water; organisms are made up mostly from water and require it more than any other molecule. 21

22 Properties of Water Adhesion Cohesion Surface tension Capillary attraction High heat capacity Low density as a solid Good solvent 22

23 Cohesion & Adhesion Adhesion water is attracted to other materials Cohesion water is attracted to other water molecules Result of hydrogen bonding between oxygen end of one water molecule and the hydrogen end of another 23

24 Surface Tension cohesion of water molecules at the surface of a body of water all the water molecules on the surface of a quantity of water (a bead, cup, pond, etc.) are 'holding' each other together, creating surface tension 24

25 Surface Tension Surface tension allows water striders to 'skate' across the top of a pond. Many objects are heavier than water, but because of surface tension, the water is able to hold up the metal. Surface tension is not the force that keeps boats floating. Archimedes' Principle: the buoyant force acting on an object placed in a fluid is equal to the weight of the fluid displaced by the object. 25

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27 Capillary Action related to adhesive properties of water click here for demonstration water 'climbs' up the straw as the water molecules are attracted to the straw molecules when one water molecule moves closer to the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw. 27

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29 Low Density as a Solid 29

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31 Why don t oceans freeze as easily as fresh water lakes? 1. Cohesion 2. Heat capacity 3. Ice floats 4. Water is a good solvent 31

32 Fish live in water. What property of water is important for the survival of fish during the winter? 1. Cohesion 2. Heat capacity 3. Ice floats 4. Water is a good solvent 32

33 True or False? (1) Water contracts (gets smaller) when it freezes. (2) Water has a high surface tension. (3) Condensation is water coming out of the air. (4) More things can be dissolved in sulfuric acid than in water. (5) Rainwater is the purest form of water. (6) It takes more energy to heat water at room temperature to 212 o F than it does to change 212 o F water to steam. (7) If you evaporate an 8-inch glass full of water from the Great Salt Lake (with a salinity of about 20% by weight), you will end up with about 1 inch of salt. (8) Sea water is slightly more basic (the ph value is higher) than most natural fresh water. (9) Raindrops are tear-shaped. (10) Water boils at a lower temperature at Denver, Co. than at the beach. 33

34 Take Home Message Properties of water: Adhesion water is attracted to other materials Cohesion water is attracted to other water molecules Surface tension - cohesion of water molecules at the surface of a body of water Capillary attraction ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity 34

35 Take Home Message Properties of water: High heat capacity water absorbs a lot of heat before the temperature rises Low density as a solid water molecules are further apart in solid water (ice) Good solvent because water is a polar molecule, it is easily attracted to many other different types of molecules 35

36 Acids & Bases Acid: substance that increases the hydrogen ion (H + ) concentration in a solution Base: substance that removes hydrogen ions from a solution, resulting in an increase in the hydroxide ion (OH - ) concentration. 36

37 Acid The acidity of a liquid (aqueous solution) is measured as its concentration of hydrogen ions. ph scale: logarithmic units; one-unit difference in ph (for example, from ph 3 to ph 4) represents a ten fold difference in the concentration of hydrogen ions ph 0 very acidic ph 7 neutral ph 14 very alkaline (basic) 37

38 ph scale 38

39 Acid Sour Reactive (corrosive) Examples Vinegar Citrus juice Stomach acid 39

40 Bases Bitter Slippery Examples Baking soda Alka-Seltzer, TUMS, etc. OH ions bind with excess H + ions, neutralizing stomach acid Milk of magnesia Household cleaners 40

41 Take Home Message 0 acid ph < 7 7 < base ph 14 An acid is a substance that increases the hydrogen ion concentration in a solution; a base removes hydrogen ions, resulting in an increase in hydroxide ion concentration 41

42 Organic Compounds Substances that contain carbon Carbon occurs in almost every chemical compound found in living things Four main types of organic compounds in living things: carbohydrates proteins lipids nucleic acids (more later) 42

43 Organic Compounds One of the more important properties of carbon is its ability to form long chains or sheets. 43

44 Organic Compounds One of the more important properties of carbon is its ability to form long chains or sheets. 44

45 Organic Compounds One of the more important properties of carbon is its ability to form long chains or sheets. 45

46 Biomolecules Complex compounds in food, such as proteins, fats, and carbohydrates, are broken down into smaller molecules in the body to produce energy. Energy that is not needed immediately is stored in biochemical compounds for later use.

47 Carbohydrates are macromolecules that function as fuel compounds that contain carbon, hydrogen, and oxygen, generally in a 1:2:1 ratio (CH 2 O) "carbo-" (from carbon) and "-hydrate" (from water). naturally occurring compounds that are essential sources of energy for all living things 47

48 If you were going to build a large macromolecule or polymer it needs to be strong. What type of chemical bond do you think would work best for building macromolecules? 1. Covalent 2. Ionic 3. Hydrogen 48

49 Carbohydrates C, H, and O (usually 1:2:1) "carbo-" (from carbon) and "-hydrate" (from water). Primary fuel for organisms Cell structure 49

50 Energy is in the chemical bonds! 50

51 Simple sugars are the most effective source of energy. Monosaccharides 3 7 carbon atoms Glucose, galactose and fructose 51

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53 Glucose Most carbohydrates ultimately converted into glucose Blood sugar 53

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55 When you eat a candy bar you are eating mostly simple sugars. If you eat a candy bar while watching a movie, how will your body utilize those sugars? 1. All of the sugars will be used immediately by your working muscles. 2. The sugars will likely be stored as glycogen. 3. The sugars will likely be stored as fat. 4. Both 2 and 3 are correct. 55

56 Complex carbohydrates are time-released packets of energy. More than 1 sugar (monosaccharide) unit Disaccharides sucrose lactose Polysaccharides starch cellulose 56

57 Chemical Fuel Preliminary Processing 57

58 Starch > 100 s of glucose molecules joined together Barley, wheat, rye, corn, and rice Glycogen animal starch 58

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60 Not all carbohydrates are digestible. Chitin Cellulose 60

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63 Lipids Why does a salad dressing made with vinegar and oil separate into two layers shortly after you shake it? Hydrophobic Hydrophilic 63

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65 Fats are tasty molecules too plentiful in our diets. Glycerol: head region Fatty acid tails Triglycerides 65

66 Fat molecules contain much more stored energy than carbohydrate molecules. 66

67 Saturated and Unsaturated Fats # of bonds in the hydrocarbon chain in a fatty acid Health considerations 67

68 What are trans fats? Many snack foods contain partially hydrogenated vegetable oils. Why might it be desirable to add hydrogen atoms to a vegetable oil? 68

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71 Which answer below is solid at room temperature? 1. Saturated fat (like animal fat) 2. Unsaturated fat (like canola oil) 3. Trans fat (like margarine) 4. Both 1 and 3 are correct. 71

72 Cholesterol and phospholipids are used to build sex hormones and membranes. Not all lipids are fats The sterols 72

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74 Steroid Hormones Estrogen Testosterone synthetic variants of testosterone 74

75 Phospholipids and Waxes Phospholipids are the major component of the cell membrane. Waxes are strongly hydrophobic. 75

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77 Proteins are versatile macromolecules that serve as building blocks. 77

78 Amino Acids Twenty different amino acids Strung together to make proteins 78

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80 Proteins are an essential dietary component. Growth Repair Replacement 80

81 Food labels indicate an item s protein content. Why is this insufficient for you to determine whether you are protein deficient, even if your protein intake exceeds your recommended daily amount? 81

82 Complete Proteins Have all essential amino acids Incomplete proteins Complementary proteins 82

83 Which answer below will provide all of the essential amino acids in a meal? 1. Hamburger 2. Corn and a legume (complementary) 3. Apple 4. Both 1 and 2 are correct. 83

84 Protein functions are influenced by their three-dimensional shape. Peptide bonds 84

85 Primary Structure The sequence of amino acids 85

86 Secondary Structure Hydrogen bonding between amino acids The two most common patterns: twist in a corkscrew-like shape zig-zag folding 86

87 Tertiary Structure Folding and bending of the secondary structure Due to bonds such as hydrogen bonds or covalent sulfur-sulfur bonds. 87

88 Quaternary Structure When two or more polypeptide chains are held together by bonds between the amino acids on the different chains. Hemoglobin 88

89 Egg whites contain much protein. Why does beating them change their texture, making them stiff? 89

90 Egg whites contain much protein. Why does beating them change their texture, making them stiff? 90

91 Why is wet hair easier to style than dry hair? 91

92 Why do some people have curly hair and others have straight hair? 92

93 A protein s function is most dependent on 1. its shape. 2. its size. 3. its color. 4. Both 2 and 3 are correct. 93

94 Enzymes are proteins that initiate and speed up chemical reactions. 94

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98 The active site is a groove or pocket on the enzyme surface, into which the substrate (here, a glucose molecule) binds and undergoes reaction. 98

99 An energy profile for the glucose reaction. An enzyme (green) enhances the reaction rate by lowering the amount of activation energy required to boost the reactants to the transition state at the summit of the energy barrier. 99

100 Misspelled Proteins Incorrect amino acid sequence Active site disruptions Phenylketonuria 100

101 Why do some adults get sick when they drink milk? 101