Amino Acids Flashcards
amino acids
building blocks of proteins, there are 20 coded for by our DNA
primary sequence
the unique sequence of a.a.’s in each protein predicts its conformation and the properties of side chains on each amino acid dictates the associations b/w them leading to the conformation of the protein
general a.a. structure
all of the 20 a.a.’s have a common structure: the carbon is substituted w/ an amino group, a carboxylic acid group, a hydrogen, and an individual side chain (R)
what do side chains determine?
how a protein can interact w/ other molecules
zwitterions
amino acids exist in this form at physiologic pH and the amino and carboxylic groups are charged; depending on the pKa of each side chain, the group may be charged/uncharged at physiological pH
protonation
occurs at very low pH
deprotonation
occurs at very high pH
peptide bond
chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid (condensation reaction), and the C’s and N’s of the a.a.’s form the polypeptide backbone
amino acid side chain classifications
non-polar aliphatic, aromatic, polar uncharged, sulfur-containing and charged
non-polar aliphatic amino acids properties
hydrophobic, electrons shared and no charges to interact w/ polar molecules
what are the non-polar alipathic a.a.’s?
glycine, alanine, proline, valine, leucine, isoleucine
aromatic amino acids properties
similar ring structures but each have diff. polarity
what are the aromatic a.a’s?
phenylalaline (non-polar, hydrophobic), tryptophan and tyrosine (more polar; contain N and O)
uncharged polar amino acids properties
contain electronegative O and N atoms and therefore polar, but side groups are not charged (allows them to interact w/ polar water molecules, increasing hydrophilicity)
what are the uncharged polar amino acids?
asparagine, glutamine, serine, threonine
disulphide bonds
sulfhydryl groups of 2 cysteines oxidize to form cystine; disulphide bonds are an important conformational stabilizer and often holds diff. parts of a protein molecule or 2+ chains that make up a protein molecule
charged amino acids properties
carry either a negative (acidic) charge or a positive (basic) charge
what are the charged a.a.’s?
aspartate, glutamate (negatively charged); arginine, lysine and histidine (+ve charge)
side-chain interactions
side-chain interactions
the charged groups on a.a.’s can interact with each other and this is considered an electrostatic interaction/bond
sickle cell anemia
improper protein conformation causes RBC to be sickle shaped; genetically inherited
homologs
similar proteins that have arisen from a common ancestor, often by gene duplication (mutations at the variant residue are more likely to cause problems)
polymorphisms
DNA variants that occur within a specific population at a frequency greater than 1%
posttranslational modification
the covalent and generally enzymatic modification of proteins during or after protein synthesis
blood coagulation
coagulation enzymes and substrates must assemble on a -ve surface (e.g. platelet membrane); calcium required to bridge b/w the gamma-carboxylated proteins and the membrane surface; Vitamin K is required for γ-carboxylation and this is where the drug warfarin interferes to prevent clots
what are the sulfur containing amino acids?
methionine and cysteine
