Chapter 2
The Chemical Basis of Life
I.
Basic Chemistry
A. Definitions
Term
Matter
Mass
Element
Molecule
Atom
Proton (p+)
Neutron (n0)
Electron (e-)
Atomic #
Definition
Examples
Anything that occupies space/has mass
Rock, wood, water, air
Measure of matter in an object
Weight = Mass – gravity force
Simplest type of matter with unique chemical carbon (C), hydrogen (H),
properties (92 natural)
oxygen (O), nitrogen (N)
Substance containing two or more atoms in a
H2O, CO2, NaCl, C6H12O6
fixed ratio
Smallest unit of matter that still retains the properties of an element
Positively-charged, subatomic particle in nucleus
Neutrally-charged (no charge) subatomic particle in nucleus
Negatively-charged, subatomic particle orbiting nucleus
# of p+; unique for each element
H = 1; C = 6; O = 8
Equal to # e- in neutral atom
B. Chemical bonding
Chemical Bond
Ionic Bonding
Covalent
Bonding
Description
Atom gains or loses e- & ions attracted to each other by opposite charges
Cation = positively charged ion
Anion = negatively charged ion
Nonpolar covalent bond = atoms share electrons equally
Atoms share
Polar covalent bond = one atom attracts electrons more
electrons
strongly creating partial charge
Single covalent bond = one electron pair shared between two atoms
Double covalent bond = two electron pair shared between two atoms
Triple covalent bond = three electron pair shared between two atoms
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C. Molecules
Characteristic
Molecule
Description
Two or more atoms chemically combine to form a structure that behaves
as an independent unit (H2 and H2O but not NaCl)
Molecular formula
C6H12O6
D. Intermolecular Forces
1. Hydrogen bonds
a.
Polar covalent bond between H and O, N, or F = partial charges
b.
Partial (+) charge of H attracted to partial (-) charge of O, N, or F
c.
Important in 3-D shape of molecules
2. Solubility and Dissociation
Term
Definition
Ability of one substance to dissolve in another
Solubility
Like dissolves like: polar substances dissolve in water/ non-polar in oils
Solvent dissolves solute
Dissociation Ionic compounds dissolved in water separate into cations and anions
II.
Chemical Reactions and Energy
A. Chemical reactions
B. Synthesis reactions
1. Anabolism = 2 smaller reactants combine to form larger product
2. Dehydration synthesis reaction = water comes out in synthesis
3. energy in = energy needed for reaction
C. Decomposition reactions
1. Catabolism = larger substance is broken down into smaller components
2. Hydrolysis = water used to break bonds
3. energy out; energy used to start reaction but net gain energy
D. Reversible reactions
1. Reactions generally occur in both directions
2. When rate in both directions is constant = equilibrium
E. Oxidation-reduction reactions
1. Reactions that result in exchange of electrons between reactants
2. Oxidation = loss of an electron
3. Reduction = gain of an electron
F. Energy= capacity to do work (move matter)
1. Two main types of energy
a.
Kinetic energy = energy resulting from movement of object
b.
Potential energy = stored energy
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2. Forms of kinetic/potential energy
Type
Mechanical
Chemical
Heat
Ea = energy
of activation
III.
Description
Energy from position/movement of objects
Potential energy stored in chemical bonds;
energy released when bonds are broken
Energy that flows between objects that are
at different temperatures
Examples
Circulating blood, moving limb
Energy stored in ATP - released
when third PO4 bond broken
All other forms of energy can
be converted into heat energy
G. Speed of chemical reactions
1. Ea = minimum energy reactants must have to start a chemical reaction
2. Catalysts lower the Ea so that it is easier for chemical reactions to occur
3. Enzymes = catalysts; speed up reactions without being consumed/altered
4. ↑ temperature/↑ concentration of reactants = ↑ rate of chemical reactions
Inorganic Chemistry
A. Definitions
1. Inorganic chemistry = substances w/o carbon; except CO/CO2/HCO32. Organic chemistry = substances that contain carbon
B. More definitions
Term
Solution
Solute
Solvent
IV.
Definition
Example
Substances are uniformly distributed with
Sugar water solution or salt
no clear boundary between the substances
water solution
Substance that is dissolved
Sugar in sugar water solution
Substance that is dissolving
Water in sugar water solution
C. Oxygen
1. Two oxygen molecules with double covalent bond (O=O)
2. Important reactant in metabolism
D. Carbon dioxide
1. One C bound by double covalent bonds to two O atoms (O=C=O)
2. Produced as waste product in metabolism
Organic Chemistry
A. Carbohydrates (CHO)
1. Hydrophilic = soluble in polar solvents, e.g, water (like dissolves like)
2. Function = provide energy and bulk in feces
3. Building blocks
a.
Monosaccharides (monomer)
1) Simple sugars used as source of energy
2) Examples include glucose, fructose, galactose
b.
Disaccharides
1) Two sugars joined by dehydration synthesis
c.
Polysaccharides (polymer)
1) Monosaccharides joined by dehydration synthesis
2) Starch = chains of glucose in plants
3) Glycogen = chains of glucose in animals
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B. Lipids
1. Hydrophobic = soluble in nonpolar solvents e.g, oils (like dissolves like)
2. Types
a. Fats (95% triglycerides)
1) Important in energy storage
2) Glycerol linked by dehydration synthesis to 3 fatty acids
3) Saturated = contains only single covalent bonds (lard)
4) Unsaturated =  1 double covalent bonds (vegetable oils)
b. Phospholipids (Fig 2.18)
1) Important component of cell membranes
2) Polar (hydrophilic) at one end
3) Nonpolar (hydrophobic) at the other.
c. Steroids
1) Four-ring structure
2) Cholesterol in cell membranes + building block for steroids
3) Estrogen, progesterone, testosterone, aldosterone
C. Proteins
1. Large polar compounds
2. Function =regulation, transportation, protection, contraction, structure,
energy
3. Building blocks = amino acids joined by peptide bonds
4. Protein structure
a.
Primary = sequence of amino acids
b.
Secondary = Folding caused by H bonds (helix or pleated sheet)
c.
Tertiary = covalent bonds between sulfur atoms in amino acids
d.
Quaternary = 2 proteins associate to form a functional unit
e.
Denaturation = breaking H bonds by ↑ temp/change pH
5. Enzymes
a.
Almost always ends in –ase; lactase, sucrase, galactase, etc.
b.
Enzyme = protein catalyst that lowers Ea
c.
Active site = 3D shape forms site where specific reactant binds
D. Nucleic acids
1. Two types
a.
DNA = deoxyribonucleic acid
b.
RNA = ribonucleic acid
2. Building blocks = nucleotides (monomer) [Fig 2.24]
3. Structure (Fig 2.26)
a.
DNA
1) Double-stranded
2) Genetic material of cells copied from one generation to
next
b.
RNA
1) Single-stranded
2) Responsible for interpreting the code within DNA into
the primary structure of proteins
E. Adenosine triphosphate (ATP)
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1. Energy currency of cells because stores and provides energy
2. 3 phosphate bonds (PO4) with energy stored in last PO4 bond
3. Provides energy for other chemical reactions as anabolism or drive cell
processes as muscle contraction
4. All energy-requiring chemical reactions stop when there is inadequate
ATP
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