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Chapter 19 Amino Acids and Proteins
Learning Objectives:
1. Draw the structure for an amino acid.
2. Write the ionic form of an amino acid.
Provide both IUPAC and common names for alcohols, phenols, ethers and thiols.
2. Recognize the physical properties of alcohols, phenols, ethers and thiols.
3. Write the dehydration equations of alcohols and predict the major product when
applicable.
4, Recognize the oxidation and reduction of alcohols and predict the products from
oxidation of primary and secondary alcohols.
5. Recognize the oxidation and reduction of thiols.
Sections:
19.1 Proteins and Amino Acids
19.2 Amino Acids as Acids and Bases
19.3. Formation of Peptides
19.4 Protein Structure: Primary and Secondary Levels
19.5 Protein Structure: Tertiary and Quaternary Levels
19.6 Protein Hydrolysis and Denaturation
Recommended additional problems
19.47, 19.57
19.1 Proteins and Amino Acids
A. General structure
Cc OH
B. Amino acid stereoisomers
CHO CHO
—- + OH
CH2OH CHZOH
CO;H
——
CH,
ae a
A Hy Hc OH
COjH
x=
NHp
CHy
19.2 Amino Acids as Acids and Bases
A. Zwitterion
@ 8
H3N——CH—C-——-O
5 i
HyzN——CH— C——OH
R R
Oxytacin
Vasopressin
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B. Secondary structure (c helix and 6 sheet)
@) o helix
Peptide
~ backbone of
primary structure
@ Carbon
@& Oxygen
@ Nitrogen 2 Hydrogen bonds of
@ Raroup secondary structure ~~
@ Hydrogen
Gi) B sheet
iii) Collagen
Triple. helix 3 a-Helix peptide chains
= Consists of three alpha helix chains woven together.
= Contains large amounts glycine, proline, hydroxy proline, and hydroxylysine that
contain —OH groups for hydrogen bonding.
= Is found in collagen, connective tissue, skin, tendons, and cartilage
19.5 Protein Structure: Tertiary and Quaternary Levels
A. Cross-links in tertiary structures
(i) hydrophobic interactions
(i) hydrophilic interactions
(iii) salt bridge
(iv) hydrogen bonds
{v) disulfide bonds
OH
Hydrophilic 4 oH
interaction j
to water
o-
Hydrophobic Gi
interaction (6)
ee
"Salt bridge
* pisulfide s
S bonds
Nae? £-Pleated sheet
Hydrogen band
‘Timberake, Gensral, Oqanic. end Biaingicat Chemishy. Copyright @ Pesrenn Edueation fnc., publishing as Benjamin Cummings