Amino Acids (Serwer 2) Flashcards
Proteins are polymers of ______.
Amino acids
Common structure of amino acids
Exception to the common structure of amino acids
Proline - an imino acid
______ are compounds related by a mirror image (cannot superimpose).
Opical isomers
Amino acids have one chiral center except for _______.
Glycine - the R group is a second H atom
Electrical Charging of Amino Acids:
- A base binds a hydrogen ion produced by dissociation of water. In water, the amino group acts as a _____ and acquries a _______ charge.
- Base
- Positive charge
Electrical Charging of Amino Acids:
- An acid releases a hydrogen ion that associates with water. In water, the carboxyl group acts as an _____ and acquries a _______ charge.
- Acid
- Negative
Features that differ among the 20 common amino acids
Side chains
Aliphatic (hydrophobic) amino acids
- Glycine (gly)
- Alanine (ala)
- Valine (val)
- Leucine (leu)
- Isoleucine (ile)
Aromatic amino acids
- Phenylalanine (phe)
- Tyrosine (tyr)
- Tryptophan (trp)
Acidic amino acids
- Aspartic acid (asp) (pH 4.1)
- Glutamic acid (glu) (pH 4.1)
Basic amino acids
- Histidine (his) (pH 6.0)
- Lysine (lys) (pH 10.8)
Arginine (arg) (pH 12.5)
Aliphatic hydroxyl amino acids
- Serine (ser)
- Threonine (thr)
Aliphatic amide
- Asparagine (asn)
- Glutamine (gln)
Sulfur-containing amino acids
- Cysteine (cys)
- Methionine (met)
Imino acid
Proline (pro)
Post-translational modification of amino acids: Hydroxyproline/Hydroxylysine
- Prolyl and lysyl hydroxylases: cofactor = Vitamin C (ascorbate)
- Need hydroxylated forms for collagen
________ is the separation of molecules achieved by exposing them to an electrical field.
Electrophoresis
_______ is electrophoresis through a medium that has both buffer and gel.
Gel electrophoresis
For electrophoresis without the gel, the speed of migration is governed by the _________.
Average electrical charge per unit area of a particle
In gel electrophoresis the _____ of the particle is an additional factor.
Size (surface area)
The anode is ______ charged, while the cathode is _______ charged. Negatively charged ions, called ______, move toward the _______. Positively charged ions, called ______, move toward the _______.
- Positively
- Negatively
- Anions; anode
- Cations; cathode
Post-translational modification of amino acids: Phosphoserine (also: phosphothreonine and phosphotyrosine - signal functions)
- Kinase
- Results from cellular signaling from hormones and can lead to activation of target enzymes
Post-translational modification of amino acids: gamma-carboxyglutamic acid
- Carboxylase - Requires Vitamin K cofactor
- Post-translational modification of blood clotting factors (prothrombin)
Hydrophobic amino acid residues are most often in the _____ of water soluble proteins and includes…
Interior
Hydrophilic amino acid residues are most often on _____ of water soluble proteins and include…
The surface
Structure breaking amino acids
- Glycine - no side chain, which causes high thermal motion in the neighborhood of glycines (room to jiggle; collagen triple helix needs glycine, about 1/3)
- Proline - Rigidly in a conformation inconsistent with either alpha helix or beta sheet (too rigid in wrong conformation)
Difference between normal hemoglobin and sickle cell
Charged residue (glutamate) is replaced with a hydrophobic residue (valine)
What does chirmal mean when referring to an amino acid?
Mirror image cannot be superimposed
What is the only amino acid found in proteins that does not exist as D-, L- isomers?
Glycine
Which of the following amino acid side chains ahve the same carbon skeleton?
-Ala, Gly, Thr, Leu, Trp, Cys
Ala, Thr, Cys
The disease scurvy is caused by dietary deficiency of vitamin C. Why is loss of teeth a symptom of this disease?
Affects the collagen; ligaments holding teeth fall apart
Which are the structure breaking amino acids?
Glycine and Proline
Which form of the cysteine side-chain funcational group is depticted? Is it protonated acidic form or the unprotonated form? What would the other form look like and what would its charge be in comparison to the form shown?
- Protonated
- S-
If normal hemoglobin moves to the anode (+pole) during electrophoresis, and is converted to sickle cell hemoglobin by replacement of glutamic acid with a valine, then what effect will this change in charge have on the speed of sickle cell hemoglobin during electrophoresis?
Move less rapidly
