Flashcards in Biochemistry Amino Acids Deck (17):
What is the isoelectric point of an amino acid?
The isoelectric point is the pH at which the molecule is electrically neutral. It will be dipolar having one positive charge and one negative charge.
What is the isoelectric point of non-ionizable amino acids?
The ISP is around 6 due to the formula:
ISP= pKa1 + pKa2 / 2
What is the formula to calculate the isoelctric point for acidic amino acids?
ISP = pka(side chain) + pkA (COOH) / 2.
This is usually an acidic value around 2-3.
What is the relationship between pH and pKa?
If the pH is less than the pKa then the species is protonated.
If the pH is greater than the pKa then the species is deprotonated.
What is the relationship between pH, pKa, and titrations?
When the pH is close to the pKa then the solution will act like a buffer. This area will be a flat line on a titration curve.
What are the key amino acid pKa values?
Alpha Carbonyl group: 2
Alpha Amino group: 9
Side carbonyl group: 4.2
Side amino grou: 10.5
What is the sterochemistry of amino acids?
All amino acids, except glycine, are chiral.
What is the fischer projection for amino acids?
L amino acids have the amino group on the left to to form the S absolute confirmation EXCEPT CYSTEINE.
How are peptide bonds formed in amino acids?
Peptide bonds are formed via a condensation reaction with the removal of water. A bond is formed between the carbonyl group and the amino group. This bond is partially double bond in character so there is no free rotation.
What is the formula for isoelectric points in a basic amino acid?
ISP= pKa (Side chain) + pKa (amino group) / 2
Describe the hydrolysis of proteins.
Water acts to break the peptide bond. A hydrogen is added to the nitrogen and OH is added to the carbonyl group.
What is the formula for calculating pH?
pH = - log [ H+ ]
In what order are amino acids formed in terms of the C and N terminal?
Amino acids start from the N terminus and build toward the C terminus.
What is unique about proline's structure?
The structure causes kinks in the secondary structure of proteins.
Describe the secondary structure of proteins.
Comprised by hydrogen bonds between the peptides. Two forms, either alpha or beta.
What are the types of bonds in tertiary structure?
Covalent disulfide bonds
Van der Vaals