Amino acids(AA, peptides, proteins) Flashcards
Define proteinogenic?
‘Protein creating’
How many natural proteinogenic amino acids are there?
20
What form of chirality are amino acids incorporated into (translated) proteins?
L-amino acids ONLY
How many amino acids are hydrophillic?
10
How many amino acids are hydrophobic?
10
What characteristics do the hydrophilic amino acids have?
2, have negative charge
3, have a positive charge
5, are polar uncharged
What characteristics do the hydrophobic amino acids have?
3, are aromatic
7, are non-polar aliphatic
How do the aromatic R-groups absorb light?
These aromatic rings absorb light at particular wavelengths (in the ultra violet spectrum) allowing them to be used to monitor proteins (e.g. their concentration).
How do amino acids join together?
Condensation reaction.
Removes water leaving aa residues. It requires energy and is performed by ribosomes.
What is the bond formed between amino acids?
Peptide bond.
If two monomers are joined then what bond is formed?
dipeptide.
What does a polypeptide chain begin and end with?
Begins with a free amino acid terminus and ends with a carboxyl group.
Why are some amino acids modified?
To add extra functional groups for added function.
What decides the structure and properties of a protein(polypeptide)?
sidechain (R groups)
How many ionizable protons does an amino acid have?
At least two each with its own pKa.
At what pH is a carboxylic acid protonated?
Carboxylic acid has an acidic pKa value and will be protonated at an acidic (low) pH.
At what pH is an amino group protonated?
The amino group has a basic pKa and will be protonated until basic pH (high).
At low pH, the amino acid exists in a _________ charge form(______)
positively
cation
At high pH, the amino acid exists in a ___________charged form (______).
negatively
anion
What is a zwitterion?
A molecule with an equal number of positive and negative charges, resulting in a net charge of zero.
What is the equation for the isoelectric point(equivalence point, pl)?
pI=pK1+pK2/2
At what pH do Amino Acids(AA) carry zero charge?
the pl.
-AA is least soluble in water
-AA does not migrate in electric field.
