Amino Acids

Created by

Keely Smith

Cards (49)

all molecules with a chiral center are optically active, meaning they rotate plane polarized light.
Glycine is the only amino acid that is not optically active.
The amino acid residues in protein molecules are exclusively L stereoisomers
Prolines secondary amino group is held in a rigid conformation that reduces the structural flexibility of polypeptides.
Aromatic groups: phenylalanine, tyrosine, and tryptophan
Tryptophans side chain is an indole ring
Max light absorption for tryptophan and tyrosine is a wavelength of 280nm
The aromatic amino acid, tryptophan, has the highest absorbance
Cysteine contains a sulfhydryl group that can make disulfide bonds.
Disulfide bonds form covalent links
Ornithine and Citrulline are key intermediates in the biosynthesis of arginine and in the urea cycle.
At a very low pH, the predominant ionic species of glycine is the fully protonated form.
The -COOH group of glycine loses its proton first during a titration.
The -NH3+ group of glycine loses its proton in the second stage during a titration.
Isoelectric point Equation: $pI=$ $\frac{1}{2}(pKa_{1}+$ $pKa_{2})$
Peptide bonds are formed through a dehydration reaction, meaning it loses a water in the process
Peptide bond formation is an example of a condensation reaction
Glycoproteins contain sugar groups
lipoproteins contain lipids
Glycoproteins have carbohydrates as their prosthetic group.
The solubility of proteins is lowered in the presence of salts.
In ion-exchange chromatography separation can be optimized by gradually changing the pH or salt concentration of the mobile phase.
In cation-exchange, the beads in the column are negatively charged so that positively charged groups stick to the beads.
As the length of a column increases, the resolution of two types of proteins with different charges usually improves.
Longer columns can increase analysis time, which can improve results.
As the length of time spent on the column increases, the resolution will decrease
In anion-exchange, the beads in the column are positively charged, meaning that negatively charged molecules will stick to the column.
In cation-exchange, negatively charged molecules will elute.
In anion-exchange, positively charged molecules will elute.
In size-exclusion, large proteins elute first.
Size-exclusion can be used to approximate the size of a protein being purified.
In affinity chromatography, the beads in the column have a covalently attached group called a ligand.
Salt weakens the binding of the protein to the immobilized ligand, which interferes with ionic interactions.
HPLC limits the diffusional spreading of protein bands, which improves resolution.
Electrophoresis is not usually used to purify proteins because it can affect the structure, thus messing up the function of proteins.
In electrophoresis, proteins can be visualized as well as separated, making it easier to identify the number of different proteins in a mixture.
Electrophoresis can be used to determine a proteins isoelectric point and approximate weight.
The migration of a protein in a gel during electrophoresis is a function of its size and shape.
Electrophoresis uses a detergent called SDS.
In electrophoresis with the presence of SDS, smaller proteins migrate more rapidly.