Question

Lecture 3 Identify amino-/carboxy termini, and R-group on amino acid What is chirality? Identify a carbon that is chiral (i.e., has 4 different groups attached) Chiral compounds rotate plane polarized light Memorize amino acid 1) structure, 2) classification (hydrophobic, aliphatic, aromatic, negatively charged, positively charged, polar uncharged) Be able to draw glycine (the generic amino acid) Given an amino acid structure and pKas of ionizable groups, be able to determine the charge at pH 1, pH 14, and pH 7 What is special about proline, glycine, cysteine, and histidine? What is the pKa of histidine? What is a zwitterion? How are amino acids zwitterions? What is the primary cause of the two diseases related to proteins that we discussed in class?

Answer 1

21Y Common /Greneral sto ucture of amu no ocid R R-9roup Aminogroup/ Anino terminal Cambonybic Acid Group/ Cambory 9terminal for example :- CH3 R8r oup -C NH 2 Amino 1 Corbory GiτουP HOOe qroud Alanine 2 Chirali chinality is a properx t of a compound whan its mirron tre mirro g image and the mo lacule non -superimposable is not Same to it ie s nonsupenimpossible for exarmple CH 3 1 CH3 (00C-C-NH CATOH image Alanine (non-sup oT imposable) Alanine misTor Gyeine HoN C-eoo Structure of aminoacid at different pH At PH= 1, both NHa and cooH 9roup remain proto nat ed, at .at pH 14 pου Proraλk, al form/zwiter ionie PH: 7 ne both the gr oups are depr omat eol HN-CHtg-Cod Fo-CHta-Coo HgN-CHaCoO H PH7 PH-14 PH=1

15 proune is a secona amano acid Hi IT has a pToline 1HyN-CHg-CUOH Gyene hydrogen is the amine acd anth Glyeine ato m e-atom gidechain. It is the Smallest amina aeic CHta-SH amino aaid with a sul fus Side Cham Only HaN-CI Coo fonm bridge S-S H in pep tide eam Cystine N Histidine Ran imidazo le side chan helps I+00c catalyeed reactiona im enzyme H Histidine 767 Pka istidine has 3 pka Vaalues Pkaj- 1.8, prag= 92 Pla3= 6Cfor imidazole side chain) uitterion positive and a gwitter ion gotive molecule that has both an them 1S Called charge Amno acids comtaine amd cooH both NH2 ation amd protonate to for m RHg group deprotonate to for med Cam So t N H fomm eoo anion Thus cooH eam a zwiters on is e-en0 H