Department of Physiology

1. Department of Physiology & BIOPHYSICS

2. Guided By Dr.A.K.Dwivedi

3. CONTENTS • Biophysics – Introduction • Units of Concentration of solution • Ions • Electrolytes and Non Electrolytes • Filtration • Ultra filtration • Dialysis • Surface tension

4. 9. Adsorption • 10. Diffusion • 11. Osmosis • 12. Colloid • 13. Emulsion and Suspensoid • 14. Hydrotrophy • 15. Donnan’s Equilibrium • 16. Acid Base & pH • 17. Acid base Buffer

5. BIOPHYSICS Introduction: Biophysics includes all physiochemical process occurring in the living cell and in its surrounding atmosphere that is in Intracellular fluid and extra cellular fluid. It includes: 1. Diffusion 2. Osmosis 3. Emulsion and suspensoid 4. Filtration, ultra filtration and dialysis 5. Colloids 6. Adsorption 7. Hydrotrophy 8. Donnan’s equilibrium 9. Electrolytes and electrolyte balance 10. Surface tension 11. Acid Base and pH and its balance

6. Units of concentration of solution Molar Solution: Moles of solute per liter of solution, and molecular weight in grams of solute dissolved in 1000 ml is molar solution. Ex. Mol wt of H2SO4 is 98.016 so a molar solution is 98.016 gms per 1000 ml. Moles of solute Molarity (M) = x 1000 Vol. of solution (in ml.) Unit of molarity – mol L -1 or M

7. Molality: Moles of solute per kilogram of solvent and Molal solution – Molecular weight in gram of a solute dissolved in 1000 gms of solvent. Unit of molality – mol kg-1 or m. Mole of solute Molality (m) = x 1000 Mass Of solvent (in g)

8. From the discussion of molarity and molality, it is evident that in molarity we consider the volume of the solution while in molality we take the mass of the solvent. Therefore the two are never equal. Molality is considered better for expressing the concentration as compared to Molarity because the molarity changes with the temperature because of the expansion or contraction of the liquid with temperature. However molality does not change with temperature because mass of the solvent does not change with change in temperature.

9. Normal solution: A normal solution is one which contains per liter, the amount equal to gram molecular weight of the substance divided by equivalent hydrogen atoms. Gram equiv. of solute Normality (N) = x 1000 Vol. of solution (in ml)

10. Molecular mass Normality = Molarity x Eq. mass Example: Mol. Wt. of H2SO4 is 98.016 where H+ + H+ and SO4-- ions are present. As number of replaceable hydrogen atom is 2, thin normal solution of H2SO4 will contain 98.016 divided by 2, i.e. 49.008 gms in a liter.

11. Relationship between Normality and Molarity of solution:- Molar mass Normality = Molarity x ------------------------- Equivalent mass For acids, Normality = molarity x basicity Where basicity is the number of H+ ions that a molecule of a acid can give in solution. For bases, Normality = Molarity x acidity Where acidity is the number of OH- ions that a molecule of base can give in a solution.

12. Percentage: Weight in grams of solute per 100 grams of solution is percent by weight and the same amount dissolved in 100 ml is % by volume. Gram equivalent: Is the molecular weight in grams divided by the number of valency of ions present. One milliequivalent is one thousandth of such gram equivalent.

13. IONS On an electric current being through solution of a compound in water, some elements migrate at the positive pole or anode and some at the negative pole or cathode. The charged particles are called ions. Negative ions (anions) move towards the anodes and positive ions (cations) to cathode due to attractions of unlike charges. The most important ions in the cell are K, Mg, PO4, SO4, CO3, and small quantities of Na, Cl and Ca.

14. The ions provide inorganic chemicals for cellular reaction. Also they are necessary for operation of some of the cellular control mechanism. For instance, ions acting at the cellular membrane are required for transmission of electrochemical impulse in nerve and muscle fibers.

15. ELECTROLYTES Electrolytes are compound which can be dissociated into anions and cataions on an electric current being passed. Example Acid, base, salts etc. Electrolytic ionic compound, e.g. Sodium chloride dissolved in water is called an electrolyte because it can conduct electricity. Electrolytes are important body constituents because: 1. Some conduct electricity essential for muscle and nerve function. 2. Some exert osmotic pressure, keeping body fluid in their own compartments. 3. Some function in acid base balance, as buffers to resist pH changes in body fluids.

16. A large number of compounds present in the body are not ionic, and therefore have no electrical properties. Electrolytes other than sodium and chloride include potassium, calcium, bicarbonate, and phosphate. Non- electrolytes Compounds which cannot be dissociated are called non-electrolytes.

17. FILTRATION Definition: Filtration is a process by which undissolved particle are separated from a liquid through a membrane as a result of mechanical force (filtering force). It is done through a porous substance such as a piece of linen or filter paper. This filtering force is either gravity or hydrostatic pressure – positive or negative.

19. Filtration is the bulk movement of fluid as a result of pressure difference on two side of a barrier, containing pores, through which the fluid can pass. The particles which are smaller than the holes can pass through retaining the larger ones. In the capillaries that are non-fenestrated, small molecules like Na+, Cl- come out of the gaps between endothelial cells but the corpuscles and large colloid molecules are retained.

20. The amount of filtrate formed per unit time will depend upon the pressure difference across the membrane, the surface area available, and the permeability of the membrane and inversely to the viscosity of the fluid concerned. Filtration occurs across capillaries, everywhere but in the kidney the rate of filtration is enormous because of large pressure gradient and increased permeability. In every site of filtration, it is opposed by the osmotic forces due to non-permeable particles called colloid osmotic pressure or oncotic pressure. The net filtration is determined by their counter balancing effect.

21. Whenever there is a difference of hydrostatic pressure between the two sides of a membrane, filtration will occur. Examples: - Absorption from the small intestine. passage of water, salts, food stuffs etc., from the blood stream to the tissue fluid. - Hydrostatic pressure in the capillaries being higher than in the later.

22. ULTRAFILTRATION Definition: If we try to pass a solution through a filter the solvent and other small molecules pass through while large molecules stay on the filter. Whether a given substance will pass through depends on the relative size of molecules and that of the pores in the filter. The rate of filtration can be increased by applying pressure. I t is a kind of filtration through a jelly filter on any ultra filter which serves to separate colloid solution from crystalloids and to separate particles of different size in a colloid mixture due to opposite of osmosis.

23. Example: the hydrostatic pressure in renal glomeruli is higher than that in any other capillaries of the body. Result: Water and small molecules filter through the glomeruli rapidly while proteins and blood cells do not. Filtration under pressure is called ultra filtration.

25. Physiological importance: The plasma is placed in a vessel of which one end is a colloidian membrane. Now, if a pressure is exerted on the blood plasma an ultra filtration will be separated. This separation will take out from the solution all the constituents of the plasma except the protein which has been contained in the gross plasma. This occurrence result in due to small pores of the colloidian membrane. The extra cellular fluid (ECF) is also on ultrafirtate into the plasma through the porous capillary membrane. If the counter pressure is not exerted on the plasma the ECF shall pass back into plasma.

26. DIALYSIS Definition: The process in which more diffusible materials can be separated from non-diffusible materials is called dialysis. Water solution of egg albumin and sugar has taken in the upper smaller container whose open bottom is covered with a semi permeable membrane has got selective permeability to water and sugar molecules but not to macromolecules – the egg albumin. This container is suspended (partially) in the water of a large container. Due to selective Permeability, the sugar molecules will ultimately go into the water leaving behind only albumin and little water. As the albumin is impermeable to this membrane, this will rebound from the membrane during the process of dialysis.

27. Example: Dialysis is a procedure in which the principle of diffusion is applied for the treatment of renal failure. In the patient’s blood, nitrogenous waste products accumulate and electrolytes imbalance may occur due to renal failure. A solution is prepared in which the waste products are absent, electrolyte concentration is appropriately adjusted and nutrients are provided. The solution is separated from the patient’s blood by a dialyzing membrane. The process of diffusion tends to normalize the composition of patient’s blood.

28. Physiological importance: Whenever the bigger particles are held back and only the smaller particles are allow passing through a membrane – depending upon osmotic pressure (i.e. diffusion), dialysis comes into action. For instance- - During absorption from the intestine bigger food particles are held back. - In the capillary area the bigger albumin, globulin etc particles are not ordinarily allowed to pass into tissue fluid. -It is to be noted that diffusion, osmosis and dialysis are the manifestation of the same principal (inherent molecular movement) and usually go on simultaneously.

29. SURFACE TENSION Definition:Surface tension is a manifestation of attracting forces in between atoms or molecules. As elsewhere, so also in a liquid, the molecules attract each other. Within the depth of the liquid each molecule is attracted equally from all directions. Hence the molecules can move freely in all directions. But a molecule at the liquid air surface is attracted only by the molecules within the depth of the liquid and there are relatively few molecules in the gas above the water surface to exert any upward force.

30. Consequently it tends to be pulled inward and its freedom of movements is restricted. Thus at the surface of a liquid layer is formed in which the molecules are arranged more densely. For the same reason the surface of the liquid tries to pull it together and shrinks in order to occupy the least possible area. This energy with which the surface molecules closely adhere together is called surface tension.

31. Example: Solutes alter surface tension. Inorganic salts generally rise while organic substance reduce surface tension of water. Of the later – bile salts, protein, phospholipids, oils, soaps, etc are important.

32. Physiological importance: 1.The globular shape of an oil drop in water, of the fat precipitate in milk etc, is due to surface tension. 2.Bile salts reduce the surface tension of the fat converting it into an emulsion in the intestine. This helps in digestion and absorption of the fat. 3.The formation of cell membrane is at least partly due to surface tension of cell cytoplasm.

33. ADSORPTION Definition:Adsorption is a peculiar form of combination in which substance adheres together on their surface. Introduction: It is a sort of union by surface contact. It is not true chemical reaction because no definite quantitative relation is found. The possible mechanism of adsorption as follows: 1.Surface tension: adsorption is probably a manifestation of surface tension developed from the attraction of dissimilar molecules of two substances.

35. 2.Residual valency: the Chemical nature of the particles and their residual valencies may be such as to make such a loose combination possible. 3.Electrical state: The electrical change of the particle may be of opposite nature. So that they attract each other and thus make a sort of contact combination. Failure of adsorption means that the electrical changes are similar so that they repel each other, during the process of adsorption much kinetic energy is lost and this kinetic energy appears as heat of adsorption.

36. Physiological importance: In Physiology adsorption plays a great role. Some of them as follow: 1.Enzyme action: Both the enzymes and substrate are colloid in nature is hastened. 2. The combination between toxin and antitoxin, by which they neutralize each other. 3. Various adsorption compounds formed in the body such as lecithin with protein (found in the brain) and such others. The blue compound formed by adding iodine with starch is an adsorption compound.

37. DIFFUSION Diffuse means spreading. Diffusion is a passive movement of substance in the body proceeds usually. Diffusion refers to the movement of a chemical substance from an area of a high concentration to an area of low concentration. Molecules of substance are continuously in motion. This motion is least in solid, maximum in gases and intermediate in the liquids.

40. For example: • 1.Diffusion process enables the transfer of oxygen from the alveoli to the lungs (high concentration) through the alveolar and capillary walls into the blood (low concentration). • 2. Sugar molecules heaped of the bottom of a cup of coffee that has not been steered well, in time become evenly distributed throughout the liquid by diffusion.

41. The process of diffusion is speeded up if the temperature rises and the concentration of diffusing substance is increased. Diffusion can also occur across the semi permeable membrane. Such as the plasma membrane; in this case, only those molecules able to cross the membrane can diffuse through. For example, the capillary wall is effectively a semi permeable membrane; although water can travel freely in either direction across it, the large protein in the plasma and red blood cells are too big to cross and so remain in blood.

42. Types of Diffusion • 1.Simple Diffusion • a. Simple Diffusion through lipid layer • b. Simple Diffusion through protein layer • 2. Facilitated Diffusion

43. Simple diffusion 1.Simple diffusionthrough the lipid bilayer: Nonpolar, hydrophobic molecules diffuse freely through the lipid bilayer of the plasma membrane of the cells without the help of membrane transport protein. Such molecules include O2, CO2 and nitrogen gases; fatty acids steroids and fat soluble vitamins (A, E, D & K), small alcohol and ammonia. As we already know two small uncharged polar molecules – water and urea – can diffuse through the lipid bilayer.

44. Diffusion through the lipid bilayer is important in the movement of oxygen and carbon dioxide between blood and body cells and between blood and air within the lungs during breathing. It also is the route for absorption of some nutrients and excretion of some waste of body cells.

46. 2. Simple diffusion through protein layer: The protein layer of all the cell membrane is permeable to water soluble substance. Many electrolytes diffuse through protein layer. Protein channels: The pores are present in the central lipid layer are entirely lined up by the integral protein molecules. These pores are the hypothetical pores and form the channels for the diffusion of water, electrolytes and other substance which can not pass through the lipid layer. As the channels are lined by protein molecules, these are called as protein channels fro water soluble substance.

47. Regulation of the channel: 1.Ungated channel: Some protein channels are continuously open are called as ungated channel. 2.Gated channel: The closed channels are called gated channels. , they open only when required.

48. For example: 1.In voltage gated channel open whenever there is a change in the electrical potential. In the muscles, during the excitation contraction coupling, the action potential spread through the transverse tubules of the sarcotubular system. When the action potential reaches the cisternae, large number of calcium ions diffuses from ciaternae into sarcoplasm. 2.Ligand gated channels open in the presence of some hormonal substance, during the transmission of impulse through the neuromuscular junction, acetylcholine releases from the vesicles. This acetylcholine molecules cause opening of Sodium channel in post synoptic membrane Na ions diffuse into neuromuscular junction from ECF.

49. 3. Facilitated Diffusion The water soluble substance having large molecules cannot diffuse through the protein channels. Such substances pass through the cell membrane with the help of some carrier proteins. This type of diffusion is called facilitated diffusion. By this process the substance are transported across the cell membrane faster than the simple diffusion. For example Glucose and Amino Acids.(Because the diameter of the molecule is larger than diameter of channels).