How many commonly occurring amino acids are there? correct answers There are 20 commonly occurring amino acids that are used for synthesis of proteins in all living systems
What do amino acids contain? correct answers Amino acids contain an alpha-carboxyl group, an alpha-amino group and a distinctive R group substituted on the alpha-carbon
What part of amino acids contribute to stereoisomeric forms? correct answers The alpha carbon of all amino acids except glycine is asymmetric and thus amino acids exist in at least two stereoisomeric forms.
What type of stereoisomers are found in proteins? correct answers Only the L stereoisomers are typically found in proteins.
Are amino acids monoprotic, diprotic, or triprotic? correct answers All amino acids are at least diprotic, corresponding the carboxyl and amino groups(ionizable groups) and a subsets of amino acids whose side chain possess groups that can ionize are triprotic.
What is the isoelectric point of an amino acid? correct answers The isoelectric point of an amino acid corresponds to the pH at which the net charge on the molecule is equal to zero. If the pH is below the isoelectric point the amino acid will carry a net positive charge, if the pH is above the isoelectric point the amino acid will carry a net negative charge.
How are amino acids joined? correct answers Amino acids can be joined covalently through peptide bonds involving the carboxyl group of one amino acid and the amino group of another amino acid to form peptides, polypeptides and proteins.
Amino Acid correct answers The smallest building block of proteins. They are bi-functional compounds as they have acid and amino groups. There are 20 standard amino acids.
Disulfide Bond correct answers A covalent linkage formed between the sulfhydryl groups of two
cysteine residues. This is important for protein stabilization
Amphoteric correct answers Capable of accepting and donating protons, able to serve as both an acid and a base.
Diprotic correct answers A molecule with two functional groups that can accept/donate protons; corresponding to two buffering regions on a titration curve.
Triprotic correct answers A molecule with three functional groups that can accept/donate protons; corresponding to three buffering regions on a titration curve.
Isoelectric Point correct answers The pH at which the molecule has a net charge of zero. It is calculated by adding the pKa's of the molecules and dividing by 2. Peptide Bond correct answers A covalently linkage formed between the carboxyl group of one amino acid to the amino group of a second amino acid through condensation reactions. The primary linkage of all peptide, polypeptide and protein structures
Residue correct answers A single unit within a polymer; for example an amino acid within a polypeptide chain
What is the difference between peptides, polypeptides and proteins? correct answers The difference is the length. Polypeptides are longer than peptides and after 51 amino acids polypeptides become into proteins.
Why does a protein have to be atleast 51 amino acids long? correct answers The shortest protein known is insulin which is a chain of 51 amino acids. So anything less than 51 amino acids is called a polypeptide.
What are peptides, polypetides and proteins? correct answers They are all linear polymers of amino acids.
Are amino acids stereoisomers? correct answers Yes, all amino acids, except for glycine have a chiral carbon and are therefore stereoisomers.
How are the 20 amino acids different? correct answers The 20 amino acids have different R group side chains linked to a common skeleton. The properties of these side chains define unique
characteristics of amino acids.
Why is glycine not stereoisomeric? correct answers All amino acids but glycine the alpha carbon
is bonded to four different groups creating a chiral center creating stereoisomers. Glycine does not have a chiral carbon
What kind of amino acid are biological proteins made from? correct answers Biological proteins are made almost exclusively from L amino acids.
Abbreviations: Glycine correct answers Gly G
Abbreviations: Alanine correct answers Ala
A
Abbreviations: Proline correct answers Pro
P