Chapter 4- Amino acids
What is the generic structure of an amino acid?
-Alpha carbon - Amino group -Carboxyl group -Hydrogen -R group
Disulfide bond is most abundant as an________
-amid
What is the net charge at isoelectric point?
0=no charge
Ibuprofen has how many chiral carbons? Which configuration is active? S or R?
1. S is active
What mixture of enantiomers exist in nature?
50/50
How many amino acids have uncharged polar side chains?
6. - Serine -Threonine -Asparagine -Glutamine -Tyrosine -Cysteine
How many amino acids have nonpolar side chains?
9. - Glycine -Alanine -Valine -Leucine -Isoleucine -Methionine -Proline -Phenylalanine -Tryptophan
If an amino acid has the same composition but different sequences they are said to be_____________from one another
Different
When determining L and S configurations you determine which substituent is most________________.
ionizable
When an amino acid is isoelectric at a certain pH, this pH is where it is__________.
neutral
The amino pH is 9.5, the carboxyl pH is 2.5. What is the isoelectric point?
pH=6 because that is the midpoint between the two
The amino acid derivative and modified amino acid is basically the_________
same
All amino acids are chiral except for?
Glycine
Which drug when you give both enantiomers causes toxicity and birth defects? How did they not know they were giving both?
Thalidomide The enantiomers are connected in this case
At physiological pH the N-terminus is protenated and the C terminus is deprotenated. True or False
True
The formation of a disulfide bond can be both intramolecular and intermolecular. True or False
True
Peptide bonds are no more than a regular__________
amide bond
Chirality has an effect on the shape of___________ and ___________
amino acids and proteins
What are consequences of amide (peptide) bond formation?
- Directionality (amino and carboxyl end) -No free rotation around the bond
Ionizable R groups are important in determining pI. Which amino acids have R groups that can be ionized?
- Lysine -Argenine -Histadine -Aspartic acid -Glutamic acid
What is the difference between composition and sequence?
Composition= number of each amino acids in a peptide or protein Sequence- order in which the amino acids are in
Amino acids are linked by peptide bonds at the protenated N terminus of one amino acid and the deprotenated C terminus of another amino acid through which reaction?
Condensation-loss of water.
Which amino acid is the only one that can form disulfide bonds?
Cysteine
Amino acids cannot act as both an acid and a base. True or false
False
What does it mean for a carbon to be chiral?
Have 4 different substituents
All our amino acids are in what configuration? L or S?
L
Are amino acids most or least soluable at isoelectric point?
Least soluable
Primary structure is the sequence of amino acids from what end to what end?
N-terminus to C-terminus
Forming a disulfide bond is what kind of reaction?
Oxidation (redox) reaction between 2 cysteines
What bonds link amino acids together? These bonds are also known as?
Peptide, covalent
______________is the foundation for all other elements for protein structure
Sequence
Amino acids are the building blocks for___________.
Proteins
After amino acids are incorporated into a peptide they are now referred to as amino acid__________
Residues
Amino acid derivatives and modified amino acids are?
Taking an amino acid and adding something to it
Does forming a peptide bond require energy?
Yes
What is the isoelectric point (pI)?
where the positive and negative charge are equal to 0