8.27 Peptides and Peptide Bonds

A molecule of water is eliminated for each ___ bond formed and the product is called a ___

peptide, peptide

Remaining portion of the AA in the peptide is called an

amino acid residue

N-terminal and C-terminal ends on the peptide are available for

further reaction

tRNA molecules transport _____ ______ to the ribosome

amino acids

The amino group from the amino acid is added to the ______ group of the growing peptide

carboxyl

Condensation reaction (peptide bond) is catalyzed by the

ribosome

All peptide bonds are approximately

coplanar

Rigidity of the peptide bond reduces

The degrees of freedom during folding

Three main torsion angles of a polypeptide backbone

phi, Ca-N; psi, C=O to Ca; and omega, peptide bond

Planarity of the peptide bond restricts the _____ to 180 degrees *trans) in nearly all the main chain peptide bonds

omega

The two torsion angles that can move in peptide bond

phi and psi

In rare cases omega = 0 degrees for a ___ peptide bond which usually involved ___

cis, proline

Ca carbons on opposite sites of the C=N peptide bond in the ___ isomer

trans

Ca carbons on same side of the C=N peptide bond in the ___ isomer

cis

_____ ______ between functional groups attached to Ca atoms are greater in cis configuration

Steric hindrance

cyclic nature of the proline side chain allow both cis and trans configurations to have nearly _____ energies

equivalent

Proline s found in the ___ configuration

cis

In aqueous solution, formation of a peptide bond is not favored…

thermodynamically (delta G = 10 kJ/mol at room temp)

Hydrolysis of peptide bond is thermodynamically ___ in aqueous solution

favored

Energy for peptide bond formation is provided by the hydrolysis of _____ during the process of translation of the genetic code by ribosomes

high-energy phosphoanhydride bonds (ATP)

Polypeptide refers to

chain of amino acids

Protein refers to

chain of amino acids after it folds properly

Average molecular weight of an amino acid is about

138

Based on abundance, average molecular weight o fan amino acid in a protein is around

128

Removing water molecule from peptide bond formation, average weight of an amino acid residue in a protein is

110

How to know the amount of possibile peptide sequence

20^(how many residues)

Common amino acid of protein

leucine (9.1%)

The rarest amino acid found in protein

tryptophan (1.4%)