Chapter 2 Notes:  The Chemistry of Life

Section 2-1:  The Nature of Matter
I.  Atom - From the Greek word atomos, which means “unable to be cut”; Very small in size.
A.  Structure of an atom:
1.  The atomic nucleus is located at the center of the atom and is made of:
a.  Protons – positively charged
b.  Neutrons – neutral
2.  Electrons
a. Move around the atomic nucleus in energy levels
b. Negatively charged
B.  Sketch an atom:

II.  Elements
A.  An element is a pure substance made of one type of atom
1.  More than 100 are known
2.  Only about 24 are commonly found in organisms
3.  Atomic number of an element = # protons 
ex:  carbon has 6 protons, so the atomic number of carbon is 6
4. Mass number = the sum of # protons + # neutrons
ex:  Carbon has 6 protons, 6 neutrons; the mass number of carbon is 12

5.  Isotopes – when atoms of the same element do not have the same number of neutrons; *All isotopes of an element have the same chemical properties
ex:  carbon 13 occurs when carbon has 6 protons and 7 neutrons.
6.  Elements are represented by a 1 or 2-letter symbol (see p.1086).  Be familiar with the following elements:
a.  C = carbon
b.  Na = sodium
c.  N = nitrogen
d.  O = oxygen
e.  K = potassium
f.  H = hydrogen

III.  Chemical Compounds
A.  A chemical compound is formed by combining 2 or more elements
1.  Examples:  H2O is made of 2 hydrogen atoms and
1 oxygen;
NaCl is made of 1 sodium and 1 chlorine atom
2.  The chemical properties of a compound are different from the elements that form the compound

         B.  Chemical bonds
1.  Chemical bonds hold atoms together
2.  Two types of chemical bonds:
a.  Ionic – formed when 1 or more electrons are transferred from one atom to another 
ex: NaCl (salt)
b.  Covalent – formed when electrons are shared between atoms ex:  H2O (water)
i.  Molecule – when atoms join together with covalent bonds
3.  Van der Waals Forces – an attraction between oppositely charged regions of molecules

Section 2-2:  Properties of Water (H2O)
I.  Water is a polar molecule
A.  Polar molecules are formed by unequal sharing of electrons.  For example, water is negative near the oxygen and positive near the hydrogens

         B.  Hydrogen bonds
1. form between water molecules
2.   not as strong as ionic or covalent bonds
3.  give water its special properties
C.  Special properties of water:
1.  Adhesion – attraction between molecules of different substances;
ex:  capillary action

2.  Cohesion – attraction between molecules of the same substance; ex:  surface tension

D. Mixtures are materials composed of 2 or more elements or compounds that are physically mixed
1.  Two types of mixtures:
a.  solutions – when all components are evenly spread in water
i.  solute  - substance that is dissolved
ii.  solvent – the substance that dissolves the solute (ex:  water)

1. suspensions – when all components are not completely dissolved in water

Part Two:                                  
Chapter 2 Notes The Chemistry of Life  (continued)
Section 2-2 (continued)
I.  pH scale
A.  Ranges from 0-14
B.  7 is neutral; between 0-7 is acidic; between 7-14 is basic
C.  acid – a compound that forms H+ in solution
D.  base – a compound that forms OH- in water
E.  buffer – weak acids or bases that help keep the pH in living things near the neutral range

Section 2-3 Carbon Compounds

I.  The importance of the element carbon:
A.  Carbon atoms have four electrons, which makes it easy to form large molecules, called macromolecules
B.  Carbon atoms most commonly bond with C, H, O, S,  P and N (see periodic table for element names for these)
C.  The bonds that are formed can be single, double, or triple bonds

II.  Types of macromolecules (large molecules)
A.  Carbohydrates
1.  Living things use carbohydrates as their main source of energy,  energy storage or, for structure
2.  Example:  sugar, also called glucose
3.  Made of C, H and O in a 1:2:1 ratio
4.  Monosaccharides - single sugars
5.  Polysaccharides - many sugars connected together
B.  Lipids
1.  Used to store energy; also make up the outer portion of a cell
2.  made mostly from C and H atoms
C.  Nucleic acids
1.  Store and transmit genetic information
2.  Two kinds of nucleic acids:
a. DNA
b.  RNA
D.  Proteins
1.  Functions (what they do)
a.  control the rate of chemical reactions
b.  control cell processes
c.  form structures, like bones and muscles
d.  move substances into or out of cells
e.  help fight disease inside organisms
2.  Made of C, H, O, and N
3.  The basic part of a protein is an amino acid.  Many amino acids link together to form a protein
4.  The shape of a protein (how the long chain of amino acids fold together) is important

Section 2-4:  Chemical Reactions and Enzymes

I.  Chemical reactions
A.  A chemical reaction is a process that changes one set of chemicals into another set of chemicals
ex:  CO2 + H2O  ----------> H2CO3
Reactants                                          Product

1.  Reactants – the element or compound that enters into a reaction (starting materials)
2.  Products – the elements or compounds that are produced by a reaction; the materials after a reaction
B.  Energy in Reactions
1.  Some reactions occur spontaneously and release energy; 
Some reactions require energy to occur
2.  Activation energy – the energy required for a reaction to occur
C.  Enzymes
1.  An enzyme is a protein that lowers the amount of activation energy required for a chemical reaction to occur
2.  Active site – area on an enzyme where another molecule can connect
3.  Substrate – the molecule that connects to an enzyme at the active site
4.  Enzymes only work at certain temperature and pH ranges!