chemistry of life
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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
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