Chapter # 3 - Biophysical

1. Biophysical Chemistry
Dr. Syed Irfan Raza

2. PHYSICOCHEMICAL PRINCIPLES
Biophysical chemistry aims to bridge the physical and
biological disciplines: in biological systems physical
forces and interactions are mediated through molecules,
which ultimately determine phenotype.
General laws & Principles of Chemistry & Physics are
applicable
https://www.sciencedirect.com/topics/chemistry/biophysical-chemistry

3. C h a p t e r O u t l i n e
• Water significance & Its dissociation
• Hydrogen Ion concentration & pH
• Human Body Buffers
• Solution & Types
• Colloidal State, Classification & Properties
• Diffusion & Osmosis and applications
• Donannan Membrane Equilibrium & Applications
• Viscosity & Its application
• Surface Tension & Its application
• Absorption & Adsorption
• Isotopes & Radio activity

4. Biophysical Properties - Lecture 1
Learning Objectives
Students will be able to:
• Structure of water and its Chemistry significance
• Under stand dissociation of water
• Concentration of [H+] & [OH-] in pure water and Kw
• pH and its calculation
• Define Buffers their composition & types
• Explain Mechanism of Buffers

6. 65 – 70 %
Dipole – Asymmetric structure
Hydrogen bonding – phases of H2O
• Solid
• Liquid
• Gas
H- Bonding
• Viscosity
• Surface Tension
Significance of Water

7. Dissociation of water
Pure Water is weak electrolyte
Dissociation/ Protolysis is reversible
H2O ↔ H+ + OH- / 107 molecules
OH- g. mol/L x H+ g. mol/L= kw
Kw dependent on temperature & = 0.000000000000001 or 10-14
@ 250 C
In Pure Water OH- = H+ = Hence Neutral

8. Hydrogen Ion Concentration of water
Pure Water:
Molecular weight of H2O = (2+16) = 18
1 Liter of water = 1000 grams = 1000/18 = 55.56 moles
Hence we can express:
55.56 moles of water contain = 1 H+ & 1OH-
pH = H+ ion concentration of any solution

9. 1. What is true about 55.56 moles of pure water:
a. pH = 1
b. pOH = 1
c. [H+] = 1
d. [OH-] = 7
e. Kw = 107

11. Biophysical Properties
• pH= Hydrogen Ion concentration = [H+]
• [H+] expressed in = 0 → 7 → 14
Sorenson – 1909:
pH is defined as:
The negative logarithm of H+ ion concentration
pH = -log [H+]

12. Acidic & Basic Solutions

13. B u f f e r s
pH of a solution can be easily changed by the addition of acids or base