Introductory Chemistry Chapter 2

Chemical Elements Fundamental unit in chemistry Cannot be broken down by chemical means 112 elements total Use 1-2 letter symbols for each e.g. C= carbon, Na = sodium, Cl = chorine. 26 normally present in your body 4 major ones & 8 others significant (see table 2.1)

Atoms Lowest unit of an element Nucleus-protons (+), neutrons (0) Surrounded by Electrons (-) Total charge is neutral- Protons # = electron # Proton number=atomic number- defines element

Ions, Molecules & Compounds Atoms interact in characteristic ways Describing this is chemistry When two or more atoms are held together with chemical bonds the result is a molecule. Described by the molecular formula

Molecular Formula Example: O2 = oxygen the gas H2O = water molecule has 2 atoms of oxygen bound together H2O = water Molecule has 2 atoms of H (hydrogen) and 1 atom of O (oxygen) Subscript = # of atoms of element Connected letters & numbers = molecule

Figure 2.3

Bonding attraction between atoms to form attachments = molecules Electrons grouped into shells preferred number in outer shell leads to chemical activity Can be covalent, ionic, polar covalent and Hydrogen bonds

Ionic Bonds Can donate or accept electrons from another atom -> Ions = atoms with a charge Opposite charges attract => bonding Ionic bonding

Figure 2.4 Figure 2.4

Covalent Bonds Can share electrons in outer shell -> covalent bonds e.g. water, many organic compounds unequal sharing -> polar bond some partial charges on the molecule

Figure 2.5a

Figure 2.5b

Figure 2.5c

Figure 2.5d

Figure 2.5e

Chemical Reactions- Synthesis Putting atoms together A + B => AB Eg. 2H2 + O2 => 2 H2O Synthesis in the body = Anabolism

Chemical Reactions- Decomposition Splitting Molecules apart AB => A + B Eg. CH4 => C + 2H2 Decomposition in the body = Catabolism

Other Reactions Exchange reactions Reversible reactions both decomposition & synthesis E. g. AB + CD => AD + BC Reversible reactions Go both directions E. g. AB <=> A + B

Nature of Water Good solvent for some molecules Dissolve = Hydrophilic molecules Don’t dissolve = Hydrophobic molecules Participates in chemical reactions Absorbs & releases heat slowly Needs large amount of heat to evaporate

Acid, Base & Salts Acid dissolves => H+ (1 or more) Base dissolves => OH- ( 1 or more) Acid plus base react => salt E.g. HCL + KOH => KCL + H2O acid base salt

pH Concept The concentration of H+ or OH- expressed on the pH scale 0-14 At pH = 7.0: H+conc. = OH- conc. Less than 7.0 = more H+ (acid) The smaller the number, the more H+ More than 7.0 = more OH- (alkaline) The larger the number, the more OH-

Organic Compounds Carbohydrates Lipids Proteins Nucleic acids

Carbohydrates Simple sugars = Monosaccharide Major one in body = glucose Disaccharides= 2- simple sugars bonded Formed by dehydration synthesis E.g. glucose + fructose => sucrose glucose + galactose => lactose Glucose + glucose => maltose

Figure 2.8

Polysacchharides Many sugars bonded in chains Can have branching structures not usually soluble in water Glycogen- animal carbohydrate Polyglucose Starch- plant carbohydrate Cellulose- plant polymer Polyglucose but indigestible = fiber

Figure 2.9

Lipids Insoluble in water = hydrophobic Triglycerides Phospholipids Cholesterol Steroids Fatty acids Fat soluble vitamins

Figure 2.10

Figure 2.11

Figure 2.12

Cholesterol Ring structures Used to make steroid hormones Help make membranes stiff Made in liver

Proteins Structural elements in cells Chemical catalysts Hormones Antibodies Polymers of amino acids

Amino Acid Amino group Carboxyl group Side chain ~20 different side chains A large variety of structures

Figure 2.13

Terminology Amino acids joined by peptide bond 2 = dipeptide, 3= tripeptide Many =polypeptide Functional polypeptide = protein Includes structure up to quaternary. Thus a protein may have 1 or more polypeptide chains

Enzymes Proteins serving as chemical catalysts Highly specific Efficient May be controlled

Figure 2.14

Nucleic Acids Polymer of nucleotides => Phosphate Sugar –pentose (ribose, deoxyribose) Base- 5 of them (4 per nucleic acid) Adenine (A), guanine (G), thymine (T), cytidine (C), uracil (U)

DNA Deoxyribose & A,T,G,C Bases pair: A-T & G-C Two polymers hydrogen bonded together forms a double helix Stores genetic information on protein sequences.

Figure 2.15

RNA Ribose & A,U,G,C Single chain Functions in protein synthesis Required to translate DNA to protein

ATP Specialized for energy transport in the cell Carries energy in the chemical bond between phosphate groups.

Figure 2.16