Glenco Chapter 6
Compounds and Elements
Life is composed of matter, which is anything that occupies space and has
mass.
Chemical element: A substance that cannot be broken down to other substances
by ordinary chemical means
Compound: Substance containing 2 or more elements combined in a fixed ratio
NATURAL ELEMENTS
There are about 25 of the 92 natural elements that are essential to life.
4 of the 25 elements make up 96% of the human body.
Oxygen 65.0%
Carbon 18.5%
Hydrogen 9.5%
Nitrogen 3.3%
TRACE ELEMENTS
The other 4% is composed of the trace elements.
The trace elements are essential to most organisms to carry out chemical
functions.
Calcium 1.5%
Phosphorus 1.0%
Potassium 0.4%
Sulfur 0.3%
Sodium 0.2%
Chlorine 0.2%
Magnesium 0.1%
CHEMISTRY 101
Atom: Smallest possible particle of an element that still has the
characteristics of the element
Atoms consist of protons (+), neutrons (no charge), and electrons (-).
Protons & neutrons in the nucleus.
Electrons in outer shells.
Atomic Number & Weight
Atomic number: the number of protons (2He = helium atomic number)
Mass number: Sum of protons plus neutrons in the nucleus (4He helium mass
number)
Atomic weight: the ~ weight in daltons of the nucleus
1 Dalton = 1 neutron + 1 proton
Atomic weight of helium = 4 daltons
Isotopes
Alternative forms of an atom.
Some atoms have more neutrons than protons.
Carbon isotopes:
12C (6 protons, 6 neutrons)
13C (6 protons, 7 neutrons)
14C (6 protons, 8 neutrons
Energy Levels
Potential energy is stored in electrons
The different states of energy in electrons is called energy levels or
electron shells
Shell closest to the nucleus has the lowest amount of energy
The shells increase in energy as they move out from the nucleus
BONDING
Ionic bonds are attractions between ions of opposite charge (NaCl).
Covalent bonds: 2 atoms share outer-shell electrons (oxygen O2).
Hydrogen Bonds: charged regions on each molecule are attracted to the
oppositely charged regions of nearby molecules (water H2O).
Chemical Reactions
The making or breaking of chemical bonds, leading to changes in composition
of matter
Starting materials are called reactants
End results are called products
6 CO2 + 6 H2O
C6H12O6 + 6 O2
Energy of Activation
Energy of activation (EA): The amount of energy needed to start the reaction.
Also referred to as the EA barrier.
Enzyme
A protein molecule that serves as a catalyst that increases the rate of
reaction without being changed itself.
(lowers EA)
How Enzymes Work
Substrate: A reactant in a chemical reaction.
Active site: Substrate specific site on enzyme that binds to substrate.
Induced fit: Substrate in the active site causes site to change shape to snug
fit
Environmental Affects on Enzymes
Temperature: Changes 3-D shape.
Salt: Salt ions interfere with chemical bonds
pH: Usually neutral (Acid rain)
Denaturation: The unraveling of enzymes from environmental affects
The Structure of Water
Polar molecule: A molecule which opposite ends have slight opposite charges
Slight charge allows for hydrogen bonds to form
Water Properties
Cohesion: The tendency for molecules of the same kind to stick together
Adhesion: The tendency for molecules of different types to stick together
Cohesion and adhesion allows water to move up a plant
ICE
Water is less dense as a solid than a gas
Ice floats because of this
This keeps lakes and oceans from freezing solid
This is a good thing if you are a fish
“Water is the Solvent of Life”
Solution: A liquid that is completely homogeneous mixture of 2 or more
substances
Solvent: The dissolving agent agent of a solution
Solute: The substance that is dissolved
Aqueous solution: One in which water is the solvent
ACIDIC & BASIC CONDITIONS
Acid: A compound that donates H+ ions to solutions.
Base: A compound that accepts H+ ions from a solution
Acidity of a solution is measured using the pH scale.
7 neutral, less than 7 acidic, more than 7 basic
Buffers
Substances that minimize changes in the concentration of H+ and OH- in a
solution
Buffers in your blood keep the pH at 7.4
If blood pH drops to 7 or rises to 7.8 it is fatal
Organic Chemistry
Organic compounds: Compounds synthesized by cells and contain carbon
Hydrocarbons: Compounds composed only of carbon and hydrogen.
Hydrocarbon structures.
MACROMOLECULES
Proteins: A type of covalently connected molecules. (enzymes)
Nucleic acids: DNA, RNA
Carbohydrates: Sugars
Lipids: The fats
MACROMOLECULES PARTS
Polymers: (polys - many, meros - parts) a chain of smaller organic molecules.
Monomers: (mono - single) The building blocks of polymers.
MAKING MACROMOLECULES
Dehydration synthesis: Linking monomers to form polymers by the removal of
water.
Hydrolysis: Unlinking polymers to form monomers by the addition of water.
CARBOHYDRATES
Disaccharide: Two monosaccharides linked together by dehydration synthesis.
Glucose + Glucose - water = Maltose
Polysaccharide: Many monosaccharides linked together by dehydration
synthesis.
Starch
Storing Carbs
Animals store excess carbohydrates in the form of glycogen
Plant store excess carbohydrates in the form of cellulose and starch
LIPIDS
Compounds consisting mainly of carbon and hydrogen atoms linked by nonpolar
covalent bonds.
Hydrophobic, Oils & fats
FATS
Glycerol and fatty acid joined by dehydration synthesis.
Triglyceride: Glycerol with 3 fatty acid chains.
Unsaturated: Having less than the maximum number of hydrogens.
Saturated: Having the maximum number of hydrogens.
OTHER LIPDS
Phospholipids: Phosphorus containing 2 fatty acid chains. (cell membranes)
Waxes: One fatty acid linked to an alcohol. (coatings on fruit)
Steroids: Lipids whose carbon skeleton forms 4 fused rings. (Cholesterol)
Steroids
Lipids with carbon skeleton consisting of 4 fused rings
Cholesterol: Steroid used to strengthen cell membranes
Precursor of other steroids and hormones
PROTEINS
Proteins (proteios - first place) are one of the most important classes of
macromolecules.
Biological polymer constructed from amino acid monomers.
Enzymes: A chemical catalyst that changes the rate of reaction without itself
being changed.
AMINO ACIDS
Amino acids all have an amino group and a carboxyl group as a base. Attached
to the central carbon (alpha carbon) is a carbon chain of various length (R
group)
20 to 22 different kinds of amino acids.
LINKING AMINO ACIDS
Cells link amino acids together at the carboxyl-carbon by dehydration
synthesis.
Peptide bond: The covalent link of amino acids.
Dipeptide: 2 amino acids linked.
Polypeptide: Chain of more than 2 amino acids.
Nucleic Acids
DNA: Deoxyribonucleic acid
Nucleic acids are polymers that are the blueprints for proteins.
Nucleotides: The monomers that make up nucleic acids which consist of:
5 carbon sugar, Phosphate group, nitrogenous base