Biochem Lecture 2 Flashcards
Go through your AA cards
Draw the basic structure of an AA at pH 7
At physiological pH, AA’s are a _______ ion.
zwitter ion
Alpha carbon on AA’s is a chiral center so what does that mean for optical isomers?
It means there will be two optical isomers, aka two enatiomers
Only L/D AA’s are found in eukaryotic proteins.
The common AA’s are called “________” AA’s
Only L amino acids are found in eukaryotic proteins
Common AA’s are called proteiogenic
How many common AA’s are there?
How many of these can humans synthesize vs how many must be consumed?
What are the essential AA’s (list them)
There are 21 common AA’s
12 of them can be synthesized
The ones that have to be consumed are called “essential AA’s”; leucine, isoleucine, lysine, valine, histidine, methionine, phenylalanine, tyrptophan, threonine
In general hydrophobic AA’s are found in the _____ of a protein.
Hydrophillic are found in _____ of a protein
Hydrophobic found on interior
Hydrophillic found on exterior
What are the beta branched AA’s?
Valine, Leucine, Isoleucine
Which are the aromatic AA’s?
Phenylalanine, Tyrosine, Tryptophan
Which AA incorporates the alpha amino group into its side chain?
Proline
What are the dicarboxylic acids?
Aspartate, glutamate (these are capable of ionizing)
What are the hydroxy AA’s?
Serine, Threonine
Carboxaminde AA’s
Asparagine, Glutamine
Which are the Diamino AA’s
Histidine, Lysine, Arginine
Arginine has a ______ group
Histidine has a _____ group
Arginine has a guanidinium group
Histidine has an imidazolium
Which of the AA’s have polar side chains?
Serine, Threonine, Asparagine, Glutamine
Cystine is a _____ AA.
It results from the oxidation/reduction of 2 cysteines?
Cystine is a derived AA
It results from oxidation of two cysteines
Creates a disulfide bridge
What kind of reaction forms a peptide bond?
A dehydration reaction
Peptide bonds have double bond character… what is the concequence of that on rotation?
At physiological pH, there is a peptide bond plane/common plane
What type of structure does pro-insulin have that when it gets turned into insulin it becomes one molecule and not two?
Disulfide bridges from cystine
Which AA’s are basic.
Which AA’s are acidic
Basic: Lysine, Arg
Acidic: Aspartate, Glutamate
If pH > pI, then the protein will be ____
If pH < pI then the protein will be ____
What is pI?
pH > pI means negative protein
pH < pI means positive protein
pI is the isoeletric point, pH at which the molecule carries no net charge
Explain where the phi and psi angles are on a peptide
Explain how to find the net charge of an AA at physiological pH (pH=7)
the COOH and the NH3 group cancel each other out so you only have to figure out which AA’s are charged and count them up
+1 : Lysine, Arginine, Histidine
-1 : Aspartate, Glutamate
Explain how titration works. Draw the peptides at different pH’s and what their charges are going to look like.
How does 2D electrophoresis work?
You first seperate things based on their apparent molecular weight.
Then, you seperate them based on charge (pI).
