Biophysics Notes PDF

Measurement Errors and Physical Quantities: The measurement error is: ○ Systematic. Dimensional equation of pressure PP: ○ [P] = M \cdot L^{-1} \cdot T^{-2} ] Intensive quantity: ○ Temperature. Van der Waals Forces: Van der Waals forces are:...

Measurement Errors and Physical Quantities: The measurement error is: ○ Systematic. Dimensional equation of pressure PP: ○ [P] = M \cdot L^{-1} \cdot T^{-2} ] Intensive quantity: ○ Temperature. Van der Waals Forces: Van der Waals forces are: ○ Physical interactions. ○ Weaker than intramolecular forces. Cryoscopic Depression and Osmolality of Plasma: Cryoscopic depression in plasma: ○ 0.53ºC. Using the constant K=1.86ºC⋅kg⋅mol−1K=1.86ºC⋅kg⋅mol−1, the osmolality of plasma is: ○ 0.28 osmol/kg. Gaseous State: The gaseous state: ○ Is fluid. ○ Has variable mass density. Gas Mixture – Molar Fraction: Molar fraction of a gas in a mixture: ○ Represents the number of moles of the gas per total number of moles in the mixture.  ○ Equal to the volume occupied by the gas divided by the total volume of the mixture. Solution Properties – Molality: Molality of a solute in a solution: ○ Number of moles of solute per mass of solvent. Electrical Potential of a Dipole: The electrical potential produced by a dipole: ○ Proportional to the dipole length ll. ○ Proportional to the electric charge qq. ○ Expressed in Volts. Work of a Force: The work of a force is negative when: ○ The displacement opposes the force. ○ The speed of displacement decreases. Blood Flow and Viscosity: When blood flows at low speed: ○ Viscosity increases. ○ Red blood cells tend to aggregate. Fluid Dynamics – Bernoulli and Poiseuille Laws: Bernoulli’s theorem (horizontally flowing fluid): ○ The sum of kinetic, potential, and pressure energies is constant. Poiseuille’s law – Resistance to fluid flow: ○ Resistance decreases when pipe diameter increases. Diffusion and Electromigration of Particles: Diffusion of particles in a fluid: ○ Migration due to a concentration gradient. Electromigration of negatively charged ions through a membrane (with potential difference dVdV): ○ Ion flow increases with increasing dVdV. ○ Ion flow increases with increasing ion mobility. Convection Forces: Forces involved in convection through a membrane: ○ Pressure forces. Nernst Equation – Membrane Potential: The membrane potential (Nernst equation): ○ Influenced by temperature. ○ Depends on ion concentration on both sides of the membrane. Osmotic Effects on Red Blood Cells (RBC): A red blood cell (RBC) placed in NaCl solution shrinks because: ○ The solution is hypertonic. ○ Osmotic pressure is higher in the solution than inside the RBC. Arterial Vascular Network: In the arterial vascular network: ○ Large arteries are elastic. ○ Blood velocity in capillaries is low. Electrocardiography (ECG) and Heart Electrical Axis: ECG shows:  ○ Isoelectric QRS complex in lead DIII. ○ Positive amplitude in lead aVL. Most probable heart electrical axis orientation: ○ 30°. Key Concepts to Remember: Measurement errors like systematic errors affect accuracy consistently. Van der Waals forces are weak but essential for molecular interactions. Osmolality and cryoscopic depression indicate the concentration of solutes in plasma. Gas properties such as molar fraction and mass density vary with composition and conditions. Blood flow dynamics are influenced by viscosity, pipe diameter, and the aggregation of red blood cells. Electrical potentials generated by dipoles and the Nernst equation explain membrane potentials. Osmotic effects on RBCs provide insights into hypertonic and hypotonic environments. The vascular system balances elasticity and blood flow to ensure efficient circulation. ECG readings can indicate the orientation of the heart’s electrical axis, guiding diagnosis.