1. CHAPTER 2 CHEMISTRY OF PROTEIN
Section 1 IMPORTANT PROPERTIES OF PROTEIN FOR LIFE
Section 2 MOLECULAR COMPOSITION OF PROTEINS
Section 3 MOLECULAR STRUCTURE OF PROTEINS
Section 4 RELATIONSHIP BETWEEN FUNCTION AND
STRUCTURE
Section 5 PHYSICO-CHEMICAL PROPERTIES OF PROTEINS

2. Section 1 IMPORTANT PROPERTIES OF PROTEIN FOR LIFE
● PROTEIN CONTENS OF HUMAN BODY
Carbohydrates, Lipids, Proteins, Nucleic Acids, Water, Middle/Small Molecules, and inorganic Molecules
15~20% expressed in whole body
~45% expressed in dry weight

3. ● PROTEIN MULTIFUNCTIONS
Essential Composition of Tissues or Cells
Maintaining Growth, Renew and Repair
Oxidative Degradation for Providing Energy
Specific Roles in
Catalysis enzymes
Regulation hormones
Transport Hb lipoprotein Albumin
Mobile/Physical Exercise actin
Signaling
Storage
Defence ……

4. Section 2 MOLECULAR COMPOSITION OF PROTEINS
—— Chemical Elements
C（50~55%）,H（6~8%）,O（19~24%）,
N（13~19%, average 16%）,S（0.~4%）、
Metal-Zn, Fe, Mg, Cu…, P, I
● STRUCTURAL UNIT——AMINO ACIDS
A. Amino Acids L-α-amino acid
CHO
C — H
CH2OH
HO—
COOH
C — H
CH3
NH2—
(R)

5. B. 20 Amino Acids and Its’ Structure

6. ● PHYSICO-CHEMICAL PROPERTIES OF AMINO ACIDS
Dipolar State of Amino Acids: zwitterion
isoelectric point (pI)
B. UV Absorption: aromatic amino acids
W,Y,F at 280nm
C. Colour Reaction:
D.Ninhydrin Reaction: blue-violet, 570nm;
yellow P 440nm;
brown N
E. Peptide Formation: residues
H3N+— H
C — COO- R + —→
H O
C — C
— N— |
– H2O ‖

7. Section 3 MOLECULAR STRUCTURE OF PROTEINS
● PEPTIDE BOND、PEPTIDE PLANE AND POLYPEPTIDE φ ψ φ
● PRIMARY STRUCTURE
Amino Acid Sequences in Peptides (N to C)
● SECONDARY STRUCTURE
α-helix, ß-pleated sheet, ß-turn, random coil

10. Domain:
A distinct structural unit of a polypeptide; domains may have separate functions and may fold as independent, compact units or
Some peptide chains fold into two or more compact
region that may be connected by a flexible segment
of peptide chain, rather like pearls on a string. These compact globular units, called domain, range in size from about 30 to 400 amino acid residues. For example, cell-surface protein CD4 consists of four similar domain.

11. Motif
(Supersecondary Structure):
A distinct folding pattern for elements of secondary
structure, observed in one or more proteins; also
called a fold or supersecondary structure or
Certain combinations of secondary structure are
present in many proteins and frequently exhibit similar
functions. These combinations are called motif or
supersecondary structure. For example, HTH

12. Meek DW, DNA Repair 3 (2004) 1049–1056;
Chuikov S et al., Nature 432(2004)

13. ● TERTIARY STRUCTURY
Hydrogen Bonding,
Salting Bond,
Hydrophobic Interaction,
Disulfide bond
Van der Waal’s Force
● QUATERNARY STRUCTURE
Subunits
Prosthetic Group/Co-factor

14. Section 4 PROTEIN FUNCTION IS RELATED WITH ITS STRUCTURE
● PRIMARY STRUCTURE DECIDES FUNCTION
A. Proteins with Similar Structure have Similar Functions
B. Proteins with Different Structure have
Different Functions
C. Primary Structure Decides 2nd/3rd/4th Structure
D. Primary Structure Decides Functions
C-Y-I-Q-N-C-P-L-G-NH2
S S
C-Y-F-Q-N-C-P-R-G-NH2
ADH
Oxytocin

15. ● PROTEIN FUNCTION RELATES TO ITS CONFORMATION
A. Allosteric Effect & Allosteric Regulation
B. Denaturation/Renaturation & Function
C. Activation of Zymogen
D. Primary Structure & Molecular Diseases
active
inactive O2

16. Section 5 PHYSICO-CHEMICAL PROPERTIES OF PROTEINS
● DIPOLAR STATE & ELECTRIC POINT
A. Electrophoresis
B. Ion –exchange Chromatography
● FEATURES OF MACROMOLECULES
A. Colloid
B. Sedimentation
C. Dialysis & Ultra-filtration
D. Gel Filtration
● PRECIPITATION
A. Salting-out B. High-metal
C. Alkaline D. Organic Reagents

17. ● DENATURATION AND RENATURATION
A. Denaturation
B. Renaturation
C. Flocculation
D. Coagulation
Aromatic Amino Acids 280nm
● UV ABSORPTION
● COLOUR REACTION
A. Biuret Reaction
B. Follin’s Reaction