Chapter 3: Amino Acids Flashcards
Proteins are __________ of amino acids residue joined to its neighbor
Polymers (residue meaning lost water when one animo acid joined to another)
All 20 common acids share common ________ features
Structural
All 20 common amino acids are ____ amino acids where they have a carboxyl group & an animo group bonded to the same carbon atom (the alpha carbon)
Alpha amino
The difference in amino acids is based on their ________
Side chains (R groups)
The alpha carbon is a __________ center
Chiral center
Amino acids have sterisomers called _____________
enantiomers
The absolute configuration of the 4 substituents of carbon atoms is the _________ system
D,L system
The amino acid residues in proteins are ______ steroisomers
L
Amino acids can be classified by their ___ group
R group
Amino acids are group into groups based on their _____ which is the tendency to interact with water at pH= 7.0
Polarity
What are the 5 R groups of animo acids?
- Nonpolar aliphatic R groups
- Aromatic R groups
- Polar uncharged R groups
- Positively charged (Basic) R groups
- Negatively charged (Acidic) R groups
What are the 6 uncommon amino acids?
- 4-hydroxyproline
- 5-hydroxylysine
- 6-N-methyllysine
- Y-carboxyglutamate
- Desmosine
- Selenocysteine & pyrrolysine
Amino acids can act as ______ & ______
Acids & Bases
The amino & carboxyl group of amino acids & the ionizable R group of some amino functions as weak _____ & ____
Acids & bases
When an amino acid lacking an ionizable R group is dissolved in water a pH = 7 it exist in solution as the __________ which can act as either acid or base
dipolar ion (zwitterion)
Substances having the dual (acid-base) nature are _______ & called _____
Amphoteric, ampholytes
Titration curves can predict the __________ of amino acids
Electric charge
Isoelectric pH (isoelectric point)(pI)
The concentration pH at which the net electric charge is zero
Amino acids with an ionizable R group have a titration curve with ______ stages (or flat spots) & have 3 pKa values
3
_________ are chains of amino acids
Peptides
Two amino acid molecules can be covalently joined through a substituted amide linkage called _________ to make a dipeptide
Peptide bond
To form a dipeptide the elements of water is removed from the ________& _________ group
alpha carboxyl group & alpha amino group
Peptide bond formation is a ___________
condensation reaction
3 amino acids can form a _________< 4 can form a tetrapeptide, 5 can form a pentapeptide, etc
Tripeptide
When only a few amino acids are linked together (like 2 or 3) then its called an __________
Oligopeptide
When many animo acids are joined (Like 5 or 6) then its called a _______________
Polypeptide
In a peptide, the amino acid residue at the end with a free alpha-amino group is called _____________ residue
Amino-terminal (or N-terminal) residue
In a peptide the free carboxyl group is called the _________ residue
Carboxyl terminal (r C-terminal) residue
When an amino acids sequence of a peptide, polypeptide or protein is shown the amino-terminal end is placed on the _______ & the carboxyl-terminal end is on the _______
Left, right
Peptides are named beginning with the _________ residue
Amino-terminal residue
Acid-base behavior of a peptide can be predicted from its free ____________________ & its ionizable R group
alpha amino & alpha carboxy group
Multisubunit proteins
Have two or more polypeptide associated noncovalently
The individual polypeptide chains in a multisubunit protein may be __________ or ________
Identical or different
If at least two polypeptides chains in multisubunit proteins are identical then they are called ________ & the different units are called ________
Oligomeric, protomers
The average molecular weight of the 20 common amino acids is about _____
138
The average molecular weight if protein amino acid is near ____
128
Simple proteins
Contain only amino acids residues & no other chemical constituents
Conjugated proteins
Proteins that have permanently associated chemical components & amino acids residues
The non-amino acid part of a conjugated protein is usually called its _______
Prosthetic group
Conjugated proteins can be classified on the basis of the chemical nature of their ___________
Prosthetic group (ex. lipoproteins contain lipids)
Proteins can be _________ & _________
Separated & purified
The 1st step in an y protein purification procedure is to break open the microbial cells ( the source of a protein) & releasing their proteins into a solution called a ______________
Crude extract
Once the extract preparation is ready then the extract is subjected to _____________
Fractionation
Fractionation
Separating the proteins into different fractions on a property such as size or charge
After a protein is fractionize then the solution or protein is _________ by adding salts to selectively precipitate some proteins (unwanted proteins) (ex. ammonium sulfate is an effective salt to salt out unwanted protons)
“Salt out”
After a solution contains only the wanted proteins then its ________
Dialysis
Dialysis
Procedure that separates proteins from small solutes (keeps large proteins & can get rid of the salt added)
___________________ is a method used for fractionating proteins
Column chromategraphy
Column chromatography is a method used for ______________ proteins
Fractioning
Ion-exchange chromatography
Exploits difference in the sign & magnitude of the net electric charge of proteins at a given pH
