4. Amino Acids and Proteins Flashcards
What is an α-amino acid?
an amino acid in which the amino group is attached to the carbon atom adjacent to the carboxyl group
What is aggregation?
Several things grouped together or considered as a whole
What is chymotrypsin?
a digestive enzyme thatcleaves peptide bonds of proteins where the amide side of the bond is an aromatic amino acid like tyrosine, phenylalanine or tryptophan. Used to sequence amino acids
What us cyanogen bromide?
an inorganic compound used to sequence amino acids by cleaving the C-terminus of methionine
What is a D-configuration?
a compound that when represented as a Fischer projection with the carboxyl group pointing up, has its amine group on the right
What is a disulfide bridge?
a covalent bond between two sulfur atoms, i.e. an - S - S - bond
What is Edman degradation?
a method of sequencing amino acids in a peptide. In this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues
What is a Fischer projection?
two-dimensional representations that show the configuration of a stereocentre; horizontal lines represent bonds projecting forward from the stereocentre, vertical lines represent bonds projecting to the rear
What is gel electrophoresis?
a method for separation and analysis of macromolecules (DNA,RNAandproteins) and their fragments, based on their size and charge
What is the hydrophobic effect?
the observed tendency of nonpolar substances to aggregate in aqueous solution and exclude water molecules.
What is an isoelectric point?
the pH at which an amino acid, a polypeptide or protein has no net charge
What is an L-configuration?
a compound that when represented as a Fischer projection with the carboxyl group pointing up, has its amine group on the left
What are peptidases?
any enzyme that performs proteolysis; protein catabolism by hydrolysis of peptide bonds
What is a peptide?
a short polymer of amino acids
What is a primary structure?
the sequence of smaller molecular components that are assembled to make a biopolymer; thus for proteins and peptides it is the specific amino acids in a polypeptide chain read from the N-terminal amino acid to the C-terminal amino acid
What is a quaternary structure?
the arrangement of polypeptide monomers into a noncovalently bonded aggregation
What is a secondary structure?
the ordered arrangement (conformation) of a biopolymer; this the organised shaped of the chain of amino acids in localised regions of a polypeptide or protein, seen as sheets or coils.
What is a tertiary structure?
the three-dimensional arrangement in space of all atoms in a single polypeptide chain
What is trypsin?
a chemical used to sequence amino acids by cleaving the polypeptide chain at points where a arginine or lysine are present
What is zwitterion?
an ionic salt in which both cation and anion are part of the same molecule
What determines the behaviour of the amino acid in water and how the peptide folds?
The nature of the amino acid r-group
Are all amino acids chiral?
No - glycine is not chiral but the others are
What do horizontal lines on a Fischer projection represent?
Bonds projecting forward
What do vertical lines on a Fischer projection represent?
Bonds projecting to the rear
Which configuration is most amino acids in?
L-configuration
Which amino acid is the only R configuration using the R,S system?
Cysteine - the rest are S, except glycine which is achiral
What does cyanogen bromide do?
It is a molecule specific for cleavage of peptide bonds formed by the carboxyl group of methionine
Which amino acids does trypsin cleave?
Arginine and lysine
Which amino acids does chymotrypsin cleave?
Phenylalanine, tryptophan and tyrosine
What does edman degradation do?
Cleaves the n-terminal amino acid allowing it to be identified
