CHEMISTRY OF LIFEChapter 2

Levels of Chemical Organization

Matter – anything that occupies space and has mass

Molecules – particles of matter made up of atoms

Atoms – protons, neutrons, electrons

A Model Of The Atom – Fig. 2-2

•Atomic number is equal to the number of protons•Atomic mass is equal to the number of protons plus neutrons

IsotopesSame atomic number but different atomic mass

Compounds

CHEMICAL BONDING Ionic bond – strong electrical attraction

between ions that bare opposite electrical charges (Fig. 2-3); ionic molecules dissolve easily in water (dissociate)

Covalent bond – bond formed between two atoms that share a pair of electrons (Fig. 2-4)

Ionic Bond

Covalent Bond

Polar vs. Nonpolar Covalent Bonds

Polar Covalent Bond – electrons are not shared equally (ex. H2O)

Non Polar Covalent Bond – electrons are shared equally (ex. C-H)

Polar Covalent Bond

Hydrogen Bonding Hydrogen Bond – a weak electrical

attraction between the partial positive charge of one water molecule and the partial negative charge of another water molecule – Fig. 2-5

Inorganic Chemistry Molecules that generally do not contain

carbon; there are no C-H or C-C bonds; smaller than organic molecules

H2O is an inorganic molecule – “universal solvent”

Organisms are composed mainly of water

Dehydration Synthesis – chemical reaction in which 2 molecules become covalently bonded by removing –H from one and –OH from another, removed atoms form water(Fig. 2-6)

Hydrolysis – the breaking apart of a molecule into its monomer subunits by the addition of the components of a H2O molecule into each of the covalent bonds linking the monomers – Fig. 2-6

Acids, Bases & Salts – Fig. 2-7

Acid – a substance that releases H+ (hydrogen ions); pH<7

Base (alkaline) – a substance that releases OH- (hydroxide ions) or decreases H+ ; pH>7

Salt – substance composed of positively charged ions (not H+ ) and negatively charged ions (not OH-); usually neutral

Buffers – substances that react with strong acid or base to keep pH constant by absorbing or releasing H+ or OH- as needed; helps to maintain homeostasis

pH Scale

Organic Chemistry – Table 2-3Molecules contain H-C & C-C bonds Carbohydrates – carbon + water – Fig. 2-

8 glycogen – animals store energy in this carb. Starch – plants store energy in this carb.

Lipids – fats, oils and waxes – non polar, therefore they do not dissolve appreciably in water – Fig. 2-9, 2-10, 2-11

Phospholipids – major component of cell membranes

Triglycerides – energy storage Cholesterol – steroid lipid – component of

cell membrane; precursor to steroid hormones

Phospholipid Triglyceride

Proteins - most varied of all the organic molecules in function; enzymes, structural, hormones, immunological, membrane components – building blocks are amino acids – 2-12

Enzyme – protein that acts as a catalyst – Fig. 2-13

Co-enzyme – some enzymes don’t function unless a co-enzyme is present (vitamins may serve this function)

Nucleic Acids – DNA and RNA (genetic material) Fig. 2-14

ATP – a modified nucleotide – Fig. 2-15 The role of ATP is to transfer energy from

nutrient molecules to cellular processes