Chapter 2 - Protein Composition and Structure Flashcards
Proteins are linear polymers built of monomer units called
amino acids.
Primary structure of a protein
The sequence of amino acids linked end to end.
Secondary structure of a protein
The 3d structure formed by hydrogen bonds between amino acids near one another.
Tertiary structure of a protein
Formed by long-range interactions between amino acids.
Enzymes
The proteins that catalyze specific chemical reactions in biological systems.
Zwitterions
A molecule or ion having separate positively and negatively charged groups.
The R group of an amino acid is often referred to as the
side chain.
Which isomer of amino acids are constituents of proteins?
L amino acids
For all amino acids, the L isomer has ___ absolute configuration.
S
In acidic solution the amino group of an amino acid is
protonated (-NH3+).
In acidic solution, the carboxyl group of the amino acid is
not dissociated (-COOH).
As the pH is raised, the first group to give up a proton in an amino acid is the
carboxylic acid.
The protonated amino group in an amino acid loses a proton around pH
9
The only achiral amino acid is
glycine.
Which amino acids have more than 1 chiral center?
Isoleucine and threonine.
How many amino acids have readily ionizable side chains?
7
Peptide bond (or amide bond)
Formed by linking the alpha-carboxyl group of one amino acid to the alpha-amino group of another amino-acid.
The formation of a dipeptide is accompanied by the loss of a
water molecule.
The lifetime of a peptide bond in aqueous solution in the absence of a catalyst approaches ______ years.
1000
Each amino acid unit in a polypeptide is called a
residue.
Main chain (or backbone)
Regularly repeating part of a polypeptide chain.
The polypeptide backbone is rich in ______ bonding potential.
Hydrogen
The largest known polypeptide is ______ which consists of more than ______ amino acids.
Titin; 27000
Oligopeptides
Peptide chains made of small numbers of amino acids.
