peptides

Question 1

peptide bonds (formation and characteristics)

Answer 1

• condensation reactions
• endergonic
• occurs in ribosomes
• resonance lead to partial double bond character
• no free rotation
• almost always in trans formation

Question 2

ionization behavior of peptides

Answer 2

• peptides have characteristic titration curves and characteristic pI
• non-terminal aa do not contribute to acid base behavior (they are occupied in peptide bonds)
• ## some R groups can ionize, contributing to acid base behavior

Question 3

what is the approx pI of this peptide

Answer 3

Between 4.25 and 9.69 =~6.79

Question 4

phi Φ

Answer 4

• angle between bonds to carbonyl carbons
• rotates around a C-N bond

Question 5

psi Ψ

Answer 5

• angle between bonds to nitrogens
• rotates around C-C bond

Question 6

Ramachandran plot

Answer 6

• shows possible bond angles in a polypeptide
• darker areas mean it’s more likely to be that bond angle