Organic Chemistry Terms: Chapter 24

Front 1

α helix

Back 1

A helical peptide conformation in which the carbonyl groups on one turn of the helix are hydrogen bonded to N-H hydrogens on the next turn. Very stable

Front 2

Hydrogenolysis

Back 2

cleavage of a bond by the addition of hydrogen.

Front 3

Isoelectric pH

Back 3

the pH at which an amino acid (or protein) does not move under electrophorensis.
This is the pH where the average charge on its molecules is zero, with most of the molecules in their zwitterionic form.

Front 4

L-amino acid

Back 4

an amino acid having a stereochemical configuration similar to that of L-glyceraldehyde. This conformation is found most often in nature.

Front 5

N terminus

Back 5

the end of the peptide chain with a free or derivatized amino group.

Hint 5

It is usually on the left. The carboxyl group of _____ amino acid links it to the rest of the peptide.

Front 6

oligopeptide

Back 6

a small polypeptide, containing about four to ten amino acid residues

Front 7

peptide

Back 7

any polymer of amino acids linked by amide bonds between the amino group of each amino acid and the carboxyl group of the neighboring amino acid.

Front 8

pleated sheet

Back 8

a two-dimensional peptide conformation with the peptide chains lined up side by side.

Hint 8

The carbonyl group on each peptide chain are hydrogen bonded to N-H hydrogens on the adjacent chain, and the side chains are arranged on alternating sides of the sheet.

Front 9

peptide bonds

Back 9

the amide linkages between amino acids

Front 10

polypeptide

Back 10

a peptide containing many amino acid residues. term commonly used for molecules with a lower molecular weight than proteins

Front 11

primary structure

Back 11

the covalently bonded structure of a protein; the sequence of amino acids, together with any disulfide bridges.

Front 12

prion protein

Back 12

a protein infectious agent thought to promote misfolding and polymerization of normal protein molecules, leading to amyloid plaques and destruction of nerve tissue

Front 13

prosthetic group

Back 13

the nonprotein of a conjugated protein, such as lipids, sugars, nucleic acids, and metal complexes

Front 14

quaternary structure

Back 14

the association of two or more peptide chains into a composite protein.

Front 15

protein

Back 15

a biopolymer of amino acids. They are polypeptides with molecular weights > 6000 amu

Front 16

random coil

Back 16

a type of protein secondary structure where the chain is neither curled into an α-helix nor lined up in a pleated sheet.

Front 17

residue

Back 17

an amino acid unit of a peptide

Front 18

Sanger method

Back 18

a method for determining the N-terminal amino acid of a peptide.

The peptide is treated with 2,4 dinitrofluorobenzene (sanger's reagent), then completely hydrolyzed. The derivative amino acid is easily identified by the rest of the peptide is destroyed in the hydrolysis

Front 19

Secondary structure

Back 19

the local hydrogen-bonded arrangement of a protein.

Generally an α-helix, pleated sheet, or random coil.

Front 20

sequence

Back 20

as a noun, the order in which amino acids are linked together in a peptide

as a verb, to determine the sequence of a peptide

Hint 20

there are two definitions, one for the noun use and one for the verb use.

Front 21

simple proteins

Back 21

proteins composed only of amino acids (no prosthetic groups)

Front 22

solid-phase peptide synthesis

Back 22

a method in which the C-terminal amino acid is attached to a solid support (polystyrene beads) and the peptide is synthesized in the C-->N direction by successive coupling of protected amino acids. When the peptide is complete, it is cleaved from the solid support.

Front 23

Classical Peptide Synthesis

Back 23

any of the several methods in which the protected amino acids are coupled in solution in the correct sequence to give a desired peptide.

Front 24

Standard amino acids

Back 24

the 20 α-amino acids found in nearly all naturally occurring proteins

Front 25

Strecker synthesis

Back 25

synthesis of α-amino acids by reaction of an aldehyde with ammonia and cyanide ion, followed by hydrolysis of the intermediate α-amino nitrile

Front 26

terminal residue analysis

Back 26

sequencing a peptide by removing and identifying the residue at the N or C terminus

Front 27

tertiary structure

Back 27

the complete 3-D conformation of a protein

Front 28

transamination

Back 28

Transfer of an amino acid group from one molecule to another. a common method for the biosynthesis of amino acids, involving glutomic acid as the source of the amino group