Biological Macromolecules
A.
B.
C.
D.
Carbohydrates
Lipids
Proteins
Nucleic acids
A. Carbohydrates
General properties
– Composed mostly of carbon, hydrogen, and oxygen
– Large number of –OH groups attached to the
carbons
– Functions
• Energy source for living cells
• Certain structural components of cells
A. Carbohydrates
Monosaccharides
– “Simple sugars”
– Monomer unit of carbohydrate group
– Examples: glucose, fructose
Disaccharides
– Composed of two monosaccharide units joined together
– Examples: sucrose, lactose
Polysaccharides
– Composed of multiple monosaccharide units (100s – 1000s)
– Examples: starch, glycogen, cellulose
B. Lipids
General properties
– Biological compounds with hydrophobic components
in their molecular structures
– Functions
• Energy storage
• Structural components
Glycerides
– A major class of lipid
– Composed of a glycerol molecule attached to one,
two, or three fatty acid molecules
B. Lipids
– Generalized structure of a triglyceride:
B. Lipids
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
B. Lipids
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)
Other lipids
– Sterols: cholesterol and steroid hormones
– Waxes
C. Proteins
General properties
– Composed of chains of amino acids
– There are 20 different amino acids, each with
distinctive chemical properties
– A protein molecule may contain several hundred
amino acids
– Each different protein has its own order, or
“sequence,” of amino acids
– The correct sequence of amino acids is essential for
the protein’s function
C. Proteins
Functions
– Enzymes: enzymes are biological catalysts that
control almost every reaction in living systems
– Cellular recognition and communication
– Structural components of living cells
C. Proteins
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
C. Proteins
Peptides
– Chains of amino acids attached by peptide bonds
– May be named by number of amino acids: dipeptide,
tripeptide, tetrapeptide, pentapeptide, etc.;
Polypeptide
C. Proteins
Protein:
– A polypeptide chain with a specific biological function
– Most proteins have from about 50 up to several
hundred amino acids in their structure
C. Proteins
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 three-dimensional structure
– Quaternary structure: only in proteins with more than
one polypeptide chain; Folding of more than one
chain together
D. Nucleic Acids
General properties
– Composed of chains of nucleotides
– There are 4 different nucleotides
– A nucleic acid molecule may contain several
thousands or millions of nucleotides
– Each nucleic acid molecule has its own order, or
“sequence,” of nucleotides
– The correct sequence of nucleotides is essential for
the nucleic acid’s function
D. Nucleic Acids
Overall function.
• The sequence of nucleotides in a nucleic acid molecule
serves as a blueprint to encode the correct sequence of
amino acids for a protein. The code for a specific protein
is called a “gene.”
• Deoxyribonucleic acid (DNA): DNA molecules
(chromosomes) serve as the “master blueprint” for all of
the cell’s proteins. The DNA molecules are transmitted to
offspring during reproduction.
• Ribonucleic acid (RNA): RNA molecules serve as
“working copies” of the genes for the proteins that the cell
is making at any given time.
D. Nucleic Acids
Nucleotide structure
– A nucleotide consists of:
• Nitrogenous base
• Pentose sugar
• Phosphate group
– Nitrogenous bases:
• Purines: adenine & guanine
• Pyrimidines: cytosine, thymine (in DNA), & uracil (in RNA)
– Pentose sugars:
• Ribose (found in RNA)
• Deoxyribose (found in DNA)