Transcript BasisOfLife_HO

THE BASIS
OF LIFE
I.
Matter consists of chemical elements in pure form
and in combinations called compounds
A. An element is a substance that cannot be
broken down to other substances by chemical
reactions
1.
2.
3.
Each element consists of a certain kind of atom that
is different from those of other elements based on
the number of protons
Atoms with more or fewer neutrons than protons are
isotopes (these decay spontaneously, giving off
particles and energy = radioactive)
Atoms with more or fewer electrons than protons
are ions
B. A compound is a substance consisting of two or
more elements combined in a fixed ratio
II. Electron arrangement is involved with energy
storage and release and chemical bonding
A. Electrons are arranged in shells, or energy
levels
1.
Electrons closest to the nucleus have the lowest
potential energy
2.
Energy added to an atom excites electrons, that
is they are moved to outer shells, increasing their
potential energy
3.
Energy is released as kinetic energy when
electrons revert to inner shells
B. The formation and function of molecules
depend on chemical bonding between atoms
1.
Covalent bonds are the strongest type of bond
a. Electrons are shared by atoms
b. Energy is stored in covalent bonds and
released when molecules are broken
c. ATP is an example of a biologically important
covalent compound
2. Ionic bonds are formed by attractions between
anions (negative ions) and cations (positive ions)
a. Ionic compounds are often salts
b. In solution ionic compounds break into ions
3. Hydrogen bonds are a type of weak bond formed
by attractions between polar molecules
C. Shape is everything - the shape of a molecule, as
dictated by chemical bonds, precisely determines
molecular function
III. Macromolecules
A.
Carbohydrates
1. The simplest form of carbohydrate is a
monosaccharide with a C:H:O ratio of 1:2:1; eg.
glucose and fructose
2. Two monosaccharides bonded together is a
disaccharide; eg. maltose and sucrose
3. More than two is a polysaccharide; eg. glycogen,
cellulose, chitin, lactose, etc.
B. Lipids
1. Include fats, oils, waxes, steroids
2. All are hydrophobic, at least at one end
3. Triglycerides are made of a glycerol molecule
with three chains of fatty acids
4. Phospholipids have two chains of fatty acids and
a phosphate group; cell membranes are double
layer of phospholipids
III. Macromolecules
C.
Proteins
1. Made of chains of combinations of 20 amino acids
called polypeptides
2. Protein shape determines function
a. Primary structure is the unique sequence of
amino acids in a protein
b. Secondary structure is the folding or coiling of
amino acids in a repeat formation; helical or
pleated sheets
c. Tertiary structure is the overall three-dimensional
shape of a protein; weak bonds such as
hydrogen bonds responsible for shape
d. Quaternary structure is the result of two or more
protein subunits
3. Functions include enzymes, structure, hormones,
cell membrane receptors, immune system, etc.
Protein secondary structure
Protein primary structure
Protein tertiary structure
Protein quaternary structure
III. Macromolecules
D.
Nucleic acids store and transmit hereditary information
1. Deoxyribonucleic acid (DNA)
a. Subunits called nucleotides
1) Backbone molecules are sugar plus a
phosphate
2) Nitrogenous bases; Adenine, Thymine,
Cytosine, Guanine (ATCG)
b. Nucleotides arranged in a double helix
1) Two antiparallel nucleic acids
2) Bases attached by hydrogen bonds in
predictable pairs: A & T, C & G
2. Ribonucleic acid (RNA)
a. Single strands of nucleic acids
b. Different form of sugar
c. Thymine replaced by uracil (U)