Nitrogen and Phosphorus- containing compounds * Flashcards
(20 cards)
alpha carbons of an amino acid is attached to four groups
an amino group, a carboxyl group, a hydogen atom, and an R group. It is a chiral cterocenter in all amino acids except glycine.
All amino acids in eukaryotes are
L-amino acids. They all have S stereochemistry except Cysteine, which is R
amino acids are amphoteric, meaning
they can act as acids or bases. Amino acids get their acidic characteristics from carboxylic acids and their basic characteristics from amino groups. In neutral solution, amino acids tend to exist as zwitterions (dipolar ions).
Amino acids can be classified by their
R group. nonpolar nonaromatic amino acids include alanine, valine, leucine, isoleucine, glycine, proline, and methionine.
Aromatic amino acids include
tryptophan, phenylalanine, and tyrosine. Both nonpolar nonaromatic and aromatic amino acids tend to be hydrophobic and reside in the interior of proteins.
Polar amino acids include
serin, threonine, asparagine, glutamine, and cysteine.
Negatively charged amino acids contain
carboxylic acids in their R groups and include aspartic acid and glutamic acid.
Positively charged amino acids
contain amines in their R groups and include arginine, lysine, and histidine.
Nonpolar nonaromatic and aromatic amino acids tend to be
hydrophobic and reside in the interior of proteins.
polar, negatively charged (acidic), and positively charged (basic) amino acids tend to
be hydrophilic and reside on the surface of proteins, making hydrogen bonds with the aqueous environment.
Peptide bonds
form by condensation reactions and can be cleaved hydrolytically. Resonance of the peptide bond restricts motion about the C-N bond, which takes on partial double-bond character. strong acid or base is needed to cleave a peptide bond.
Polypeptides are made up of
multiple amino acids linked by peptide bonds.
Proteins
are large, folded, functional polypeptides.
Strecker synthesis
generates an amino acid from aldehyde. An aldehyde is mixed with NH4Cl and potassium cyanide. the ammonia attacks the carbonyl carbon, generating an imine. the imine is then attacked by the cyanide, generating an aminonitrile. The aminonitrile is hydroxylyzed by two equivalents of water, generating an amino acid.
gabriel synthesis
generates an amino acid from potassium phtalimide, diethyl, bromomalonate, and an alkyl halide. The Pthaliide attacks the diethyl bromomalonate, generating a phthalimidomalonic ester. The pthalimidomalonic ester attacks an alkyl halide, adding the alkyl group to the ester. the product is hydrolyzed, creating pthalic acid (with two carboxyl groups) and converting the esters into carboxylic acids. On carboxylic acid of the resulting 1,3-dicarbonyl is removed by decarboxylation.
Phophorys is found in
inorganic phosphate (Pi). a buffered mixture of HPO42- and dihydrogen phosphate H2PO4-
Phosphorus is found in the backbone of
DNA. Which uses phosphodiester bonds. In forming these bonds, a pyrphosphate is released. Pyrophosphate can then be hydrolyzed to two inorganic phosphates.
Phosphate bonds are
high energy because of large negative charges in adjacent phosphate groups and resonance stabilization of phosphate.
Organic phosphates are
carbon-containing compounds that also have phosphate groups. The most notable example are nucleotide triphosophates (such as ATP or GTP) and DNA.
Phosphoric acids has three hydrogens, each with a unique pKa. The wide variety in pKa values allows phosphoric acid
to act as a buffer over a large range of pH values.
