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Basic Chemistry for Biology
Element
substance that can’t be broken down into a
simpler substance
made of only one kind of atom
Atom
smallest particle of an element
made of three subatomic particles
protons ( positive charge ) in the nucleus
neutrons ( no charge ) in the nucleus
electrons ( negative charge ) orbit the nucleus
in energy levels
Electron energy levels
1st level
filled with 2 electrons
2nd level
filled with 8 electrons ( an octet )
3rd level
filled with 18 electrons
Stability
atoms are stable with filled electron levels
Isotopes
atoms of the same element with a different number
of neutrons in the nucleus
C12
( 6 p+ , 6 n0 )
C13
( 6 p+ , 7 n0 )
C14
( 6 p+ , 8 n0 )
Radioactive isotopes
used to diagnose and/or treat disease
kill bacteria on surfaces and in food
destroy rapidly growing cancer cells
imaging of body functions
Compound
substance made of two or more kinds of atoms
chemically bonded together
results in stability for all atoms involved due to
the transfer or sharing of electrons
has properties different from the constituent atoms
Bonding in compounds
Ionic bonds
electrons are transferred from one atom
to another
results in charged atoms called ions
oppositely charged ions ( positive and negative )
attracted to each other holding compound together
ionic compounds dissolve ( dissociate ) in water
ionic solutions conduct electricity
important to nerve impulses
example : NaCl
made of Na+ and Cl-
Covalent bonds
electrons shared between atoms
results in molecules
very strong bonds
examples :
H2O ( water )
CH4 ( methane )
C6H12O6 ( glucose )
Acids and Bases
Acid :
Any substance that releases H+ ions when
dissolved in water
examples: HCl, HNO3, H2SO4, H3PO4, H2CO3
Base :
Any substance that releases OH- ions when
dissolved in water
examples: NaOH , KOH , Mg(OH)2 , Ca(OH)2
Dissociation :
The ions of ionic substances come apart in water
examples:
HCl
KOH


H+
Cl-
+
K+ +
OH-
Neutralization reaction :
When mixing acids and bases, the H+ and OH- react
to form water and the solution is neither acidic nor basic
example :
HCl + NaOH

H2O + NaCl
Indicators :
Chemicals that have different colors depending on
the acidity of the solution they are in
examples:
litmus is red in acid and blue in base
phenolphthalein is pink in base
pH scale :
0-2
3-4
strong acid
5 – 6.9
7
7.1 - 9
10 - 11
12 - 14
neutral
strong base
stomach acid, battery acid
soft drinks, tomato juice
coffee, urine, milk
water
blood, sea water
detergent, rolaids
ammonia, oven cleaner
Scale only used for weak or diluted acids and bases
Many chemical reactions in living systems are sensitive to
a particular pH level
Buffer: A weak acid or base that reacts with a strong base or acid
to prevent sudden changes in pH.
Water
Makes up 70 – 95% of most living things
Many things dissolve in water so important to life processes
Molecular formula :
H2O
Shows polarity : atoms in the molecule do not share the
electrons equally so the oxygen side is
slightly negative and the hydrogens are
slightly positive
hydrogen bonding : weak bonds between water molecules
due to their polarity
Unique properties of water due to polarity and the extra
attraction caused by hydrogen bonding :
dissolves a variety of substances
surface tension
cohesion and adhesion
capillarity
high heat of fusion and vaporization
high specific heat
expands on freezing
Macromolecules
Carbohydrates
Subunit :
simple sugar
Function : structure, energy storage
Examples : sugar, starch
Lipids
Subunit :
fatty acids linked by glycerol
Function : energy storage, membranes, hormones, pigments
Examples : fats, oils
Proteins
Subunit :
amino acid
Function : structure, enzymes, hormones
Examples : muscle, hemoglobin
Nucleic acid
Subunit :
Function :
Examples :
nucleotide
5 carbon sugar
phosphate
nitrogenous base
genetic information, protein production
DNA, RNA
Metabolism
Dehydration synthesis
Combining subunits by removing water molecules
Hydrolysis
Breaking apart subunits by adding water molecules
Enzymes
Have an active site
Bind to the substrate
Lower the activation energy
Reusable