Fall 2019 MCB 102 Lecture 2 part 1 after lecture slides PDF

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Summary

Sebeeha...

Description

proteins most diverse of the polymers in a cell linear polymer of amino acids Function

Example

catalysis

enzymes

structure

cytoskeleton, hair, silk

motion

flagella, muscle

transport

pumps

messengers

hormones

sensors

receptors

Ca is chiral – 4 different substituents

2 absolute configurations Only L-amino acids in proteins

Configuration relative to glyceraldehyde

Representation of configuration around Ca

a-amino acids

R

R group is different in 20 amino acids All others (except proline) have configuration shown

amino acids have at least 2 weak acid groups

predominant form at pH = 1

predominant form at pH = 11

titration curve for glycine

what % of carboxyl groups are ionized at pH = 5.97 what % of amino groups are ionized at pH = 5.97 pI 

pK1  pK 2 2

titration curve for glutamate R = CH2CH2COOH

pI is lower than that for glycine

titration curve for histidine R=

pI is higher than that for glycine...