Ch. 2 BASIC CHEMISTRY. Copyright 2010 Pearson Education, Inc.

Transcription

1 Ch. 2 BASIC CHEMISTRY

2 Matter and Composition of Matter Definition: Anything that has mass and occupies space Matter is made up of elements An element cannot be broken down by ordinary chemical means Atoms - are unique building blocks for each element

3 Atomic Structure Neutrons No charge, In atomic nucleus Mass = 1 atomic mass unit (amu) Protons Positive charge,in atomic nucleus Mass = 1 amu

4 Atomic Structure Electrons Negative charge,orbit nucleus Mass = 0 amu Equal in number to protons in atom

5 Nucleus Nucleus Helium atom Helium atom Proton Neutron Electron Electron cloud Figure 2.1

6 Energy Definition: Capacity to do work or put matter into motion Types of energy: Kinetic: energy associated with motion Potential: stored (inactive) energy Electrical : results from the movement of charged particles (Na+, K+)

7 Identifying Elements Atoms of different elements contain different numbers of protons Compare hydrogen, helium and lithium

8 Proton Neutron Electron Hydrogen (H) Helium (He) Lithium (Li) Figure 2.2

9 Identifying Elements Atomic number = Mass number = Mass numbers of atoms of an element are not all identical Isotopes = atoms of the same element that differ in the # of neutrons they contain

10 Proton Neutron Electron Hydrogen ( 1 H) Deuterium ( 2 H) Tritium ( 3 H) Figure 2.3

11 Atoms of Elements can combine Chemically to form Molecules and Compounds Molecule: two or more atoms bonded together (H 2 or C 6 H 12 O 6 ) Compound:

12 Chemical Bonds Electrons occupy up to seven electron shells (energy levels) around nucleus Octet rule: Except for the first shell which is full with two electrons, atoms interact in order to have eight electrons in their outermost energy level (valence shell)

13 Chemically Inert Elements Stable and unreactive Outermost energy level fully occupied or contains eight electrons

14 (a) Chemically inert elements Valence shell complete 2e 8e 2e Helium (He) Neon (Ne) Figure 2.4a

15 Chemically Reactive Elements Valence shell not fully occupied by electrons Tend to gain, lose, or share electrons (form bonds) with other atoms to achieve stability

16 (b) Chemically reactive elements Valence shell incomplete 1e 4e 2e Hydrogen (H) Carbon 6e 2e 8e 1e 2e Oxygen (O) Sodium (Na) Figure 2.4b

17 Ionic Bonds Ions are formed by: Anions ( charge) have gained one or more electrons Cations (+ charge) have lost one or more electrons Attraction of opposite charges results in: An ionic bond

18 + Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na + ) Chloride ion (Cl ) Sodium chloride (NaCl) Figure 2.5

19 Covalent Bonds Formed by sharing of two or more valence shell electrons Allows each atom to fill its valence shell at least part of the time

20 Reacting atoms Resulting molecules + or Hydrogen atoms Carbon atom Molecule of methane gas (CH 4 ) (a) Formation of four single covalent bonds: Figure 2.7a

21 Reacting atoms Resulting molecules + or Oxygen atom Oxygen atom Molecule of oxygen gas (O 2 ) (b) Formation of a double covalent bond: Figure 2.7b

22 Reacting atoms Resulting molecules + or Nitrogen atom Nitrogen atom Molecule of nitrogen gas (N 2 ) (c) Formation of a triple covalent bond:. Figure 2.7c

23 Covalent Bonds Sharing of electrons may be equal or unequal Equal sharing produces: Electrically balanced nonpolar molecules

24 Covalent Bonds Unequal sharing by atoms with different electron-attracting abilities produces: polar covalent bonds H 2 O

25 Hydrogen Bonds Attractive force between electropositive hydrogen of one molecule and an electronegative atom of another molecule Important in intramolecular bonds, holding a large molecule in a three-dimensional shape

26 + Hydrogen bond (a) The slightly positive ends ( + ) of the water molecules become aligned with the slightly negative ends ( ) of other water molecules. Figure 2.8

27 Synthesis Reactions A + B AB Always involve bond formation Anabolic Endergonic

28 (a) Synthesis reactions Smaller particles are bonded together to form larger, molecules. Example Amino acids are joined to Form protein. Amino acid molecules Protein molecule Figure 2.9a

29 Decomposition Reactions AB A + B Reverse synthesis reactions Involve breaking of bonds Catabolic Exergonic

30 (b) Decomposition reactions Bonds are broken in larger molecules, resulting in smaller, less complex molecules. Example Glycogen is broken down to release glucose units. Glycogen Glucose molecules Figure 2.9b

31 Classes of Compounds Inorganic compounds Do not contain carbon (ex. Water, salts, and many acids and bases) Organic compounds Contain carbon, usually large, covalently bonded (ex s. carbohydrates, fats, proteins, nucleic acids)

32 Water 60% 80% of the volume of living cells Most important inorganic compound in living organisms because of its properties

33 Salts Ionic compounds that dissociate into ions in water Ions (electrolytes) conduct electrical currents in solution

34 Acids Acids : Proton (H+) donors (release H + in solution) HCl H + + Cl

35 Bases Bases: Proton acceptors (take up H + from solution) NaOH Na + + OH

36 Acid-Base Concentration Acid solutions contain higher amounts of H + As [H + ] increases: acidity increases Basic solutions contain higher concentrations of OH As [H + ] decreases (or as [OH ] increases): alkalinity increases ph = measure of the acidity/bascisity of a solution

37 Acid-Base Concentration Neutral solutions: ph = 7 Contains equal numbers of H + and OH Acidic solutions [H + ], ph ph = Basic solutions [H + ], ph ph=

38 Carbohydrates Sugars and starches whose building blocks = Three classes Monosaccharides -Simple sugars containing three to seven C atoms (glucose) Disaccharides -Double sugars that are too large to pass through cell membranes Polysaccharides - Three/more simple sugars, e.g., starch and glycogen; not very soluble

39 Carbohydrates Functions Primary role: Major source of cellular fuel (glucose)

40 Example Hexose sugars (the hexoses shown here are isomers) (a) Monosaccharides Monomers of carbohydrates Example Pentose sugars Glucose Fructose Galactose Deoxyribose Ribose Figure 2.15a

41 (b) Disaccharides Consist of two linked monosaccharides Example Sucrose, maltose, and lactose (these disaccharides are isomers) Glucose Fructose Glucose Glucose Galactose Glucose Sucrose Maltose Lactose PLAY Animation: Disaccharides Figure 2.15b

42 (c) Polysaccharides Long branching chains (polymers) of linked monosaccharides Example This polysaccharide is a simplified representation of glycogen, a polysaccharide formed from glucose units. Glycogen PLAY Animation: Polysaccharides Figure 2.15c

43 Lipids Insoluble in water Main types: Triglycerides Phospholipids Steroids

44 Triglycerides Defined as:solid fats and liquid oils Building blocks = three fatty acids bonded to a glycerol molecule Main functions Energy storage Insulation Protection

45 (a) Triglyceride formation + Glycerol 3 fatty acid chains Triglyceride, or neutral fat 3 water molecules Figure 2.16a

46 Phospholipids Similar to triglycerides: Building blocks = Glycerol + two fatty acids and a phosphorus (P)-containing group Head and tail regions have different properties Important in cell membrane structure

47 (b) Typical structure of a phospholipid molecule Two fatty acid chains and a phosphorus-containing group are attached to the glycerol backbone. Example Phosphatidylcholine Polar head Phosphoruscontaining group (polar head ) Glycerol backbone 2 fatty acid chains (nonpolar tail ) Nonpolar tail (schematic phospholipid) Figure 2.16b

48 Steroids Steroids interlocking four-ring structure Examples are cholesterol, vitamin D, steroid hormones, and bile salts

49 (c) Simplified structure of a steroid Four interlocking hydrocarbon rings form a steroid. Example Cholesterol (cholesterol is the basis for all steroids formed in the body) Figure 2.16c

50 Proteins Building blocks = amino acids After amino acids are linked together they often undergo a natural folding process This folding process results in four different levels of protein structure: primary, secondary, tertiary, quaternary

51 Amine group Acid group (a) Generalized structure of all amino acids. (b) Glycine is the simplest amino acid. (c) Aspartic acid (an acidic amino acid) has an acid group ( COOH) in the R group. (d) Lysine (a basic amino acid) has an amine group ( NH 2 ) in the R group. (e) Cysteine (a basic amino acid) has a sulfhydryl ( SH) group in the R group, which suggests that this amino acid is likely to participate in intramolecular bonding. Figure 2.17

52 Amino acid Amino acid Amino acid Amino acid Amino acid (a) Primary structure: The sequence of amino acids forms the polypeptide chain. PLAY Animation: Primary Structure Figure 2.19a

53 a-helix: b-sheet: (b) Secondary structure: The primary chain forms spirals (a-helices) and sheets (b-sheets). PLAY Animation: Secondary Structure Figure 2.19b

54 (c) Tertiary structure: PLAY Animation: Tertiary Structure Figure 2.19c

55 (d) Quaternary structure: Two or more polypeptide chains, each with its own tertiary structure, combine to form a functional protein. PLAY Animation: Quaternary Structure Figure 2.19d

56 Protein Denaturation Shape change and disruption of active sites due to environmental changes A denatured protein is nonfunctional

57 Enzymes Are proteins Biological catalysts Increase the speed of a reaction Allows for millions of reactions/minute

58 Enzyme Function Substrates + Active site Enzyme

59 Nucleic Acids DNA and RNA Building blocks = nucleotide, composed of N- containing base, a pentose sugar, and a phosphate group

60 Deoxyribonucleic Acid (DNA) Four Nitrogen containing bases: adenine (A), guanine (G), cytosine (C), and thymine (T) Double-stranded, helical Replicates before cell division, ensuring genetic continuity Provides instructions for protein synthesis

61 Phosphate Sugar: Deoxyribose Base: Adenine (A) Thymine (T) Sugar Phosphate (a) Adenine nucleotide Hydrogen bond Thymine nucleotide Sugar-phosphate backbone Deoxyribose sugar Phosphate Adenine (A) Thymine (T) Cytosine (C) Guanine (G) (b) (c) Computer-generated image of a DNA molecule Figure 2.22

62 Ribonucleic Acid (RNA) Four bases: adenine (A), guanine (G), cytosine (C), and uracil (U) Single-stranded PLAY Animation: DNA and RNA

63 Adenosine Triphosphate (ATP) Adenine-containing RNA nucleotide with two additional phosphate groups

64 High-energy phosphate bonds can be hydrolyzed to release energy. Adenine Phosphate groups Ribose Adenosine Adenosine monophosphate (AMP) Adenosine diphosphate (ADP) Adenosine triphosphate (ATP) Figure 2.19

65 Function of ATP Phosphorylation: The chemical energy contained in the high energy phosphate bonds can be used to perform cellular work

66 Solute + Membrane protein (a) Transport work Relaxed smooth muscle cell (b) Mechanical work Contracted smooth muscle cell + + (c) Chemical work Figure 2.20