Chemical Basis of Life
A.
Review of Basic Chemistry
1.
Atomic Structure
 Atoms: Protons, Neutrons, Electrons
 Element
 Isotope
2.
Chemical Bonding & Other Atomic
Interactions
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3.
Ionic Bonding
Covalent Bonding: Molecules
Polar Interactions
Hydrogen Bonding
Hydrophobic Interactions
Important Elements in Living Cells
Carbon (C)
Hydrogen (H)
Nitrogen (N)
Oxygen (O)
Phosphorus (P)
Sulfur (S)
Iron (Fe)
Magnesium (Mg)
Manganese (Mn)
Ionic “Mineral Salts:” sodium, potassium,
chloride, calcium, many “trace”minerals
B.
Water: Properties and Roles in Living Systems
1.
Structure of Water
2.
Hydrogen Bonding and Ionization
3.
pH
 Acids
 Bases
4.
High Heat Capacity and other Thermal
Properties
5.
Water as a solvent
 Hydrophilic
 Hydrophobic
5.
Water as a Chemical Reactant
 Monomers and Polymers
 Condensation (Dehydration)
 Hydrolysis
C.
Carbohydrates
Consist mainly of C, H, O
Large number of -OH groups
Functions: Energy storage & utilization;
structural component
1.
Monosaccharide
“Simple Sugar” with a single sugar unit
per molecule
Classified by number of carbons: triose,
tetrose, pentose*, hexose*, etc.
Examples: Glucose, fructose, galactose
2.
Disaccharide
Two monosaccharide units linked by
glycosidic bonds
Examples: Maltose, sucrose, lactose
3.
Polysaccharide
“Many” sugar units linked in chains by
glycosidic bonds
Typically hundreds to thousands of sugar
units
Polysaccharide chains may be straight or
branched
Examples: Starch, glycogen, cellulose,
peptidoglycan, chitin
D.
Lipids
All or part of the structure of a lipid is
hydrophobic
Many lipids have long hydrocarbon chains as
part of their structure
Functions: Energy storage & utilization;
structural component
1.
Glycerides
Composed of fatty acids attached to
glycerol molecules
Monoglycerides, diglycerides,
triglycerides
Fatty acid saturation:
 Fatty acids with greater saturation have
fewer C=C double bonds; have higher
melting points
 Fatty acids with less saturation have
more C=C double bonds; have lower
melting points
2.
Phospholipids
A lipid molecule (for example, a
diglyceride) with a hydrophilic group
attached via a phosphate linkage
Found in membrane structure (details
later in course)
3.
Other Lipids
Sterols: Cholesterol and Steroid
Hormones
Waxes
E.
Amino Acids and Proteins
1.
Amino Acid Structure
To the central carbon atom, four things
are attached:
 Hydrogen atom
 Amino group
 Carboxylic acid group
 Side chain “R” group
Twenty different “R” groups, with different
chemical properties
2.
Peptides
Chains of amino acids attached by
peptide bonds
May be named by number of amino acids:
dipeptide, tripeptide, tetrapeptide,
pentapeptide, etc.; Polypeptide
Protein: A polypeptide chain with a
specific biological function
Most proteins have from about 50 up to
several hundred amino acids in their
structure
3.
Levels of Protein Structure
Primary structure: Amino Acid Sequence
Secondary Structure: Localized folding of
a chain into regions of helix or sheet
structure
Tertiary Structure: Folding of a single
polypeptide chain into a threedimensional structure
Quaternary structure: Only in proteins
with more than one polypeptide chain;
folding of more than one chain together
4.
Functions of proteins
Enzymes
Regulatory Molecules
Cell Recognition
Structural Components
F.
Nucleic Acids
1.
Nucleotide Structure
A nucleotide consists of:
Nitrogenous Base
Pentose Sugar
Phosphate Group
Nitrogenous Bases:
Adenine & Guanine (Purines)
Cytosine, Thymine, & Uracil (Pyrimidines)
Pentose Sugars:
Ribose
Deoxyribose
2.
RNA & DNA
Ribonucleic Acid: Polymers of ribose
nucleotides, with A, C, G, & U bases
Deoxyribonucleic Acid: Long polymers of
deoxyribose nucleotides, with A, C, G, & T
bases
DNA is typically a double-stranded helix:
A pairs with T, C pairs with G
Function: Encoding the Amino Acid sequence
of proteins:
The sequence of nucleotides in the
nucleic acid of a gene determines the
sequence of amino acids in the protein
that the gene encodes.
3.
Other Nucleotides & Their Functions
Several specialized nucleotides serve as
enzymatic cofactors in metabolism, involved
with energy conversion & conservation.