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BIOPHYSICS:PRINCIPLES ANDBIOMEDICAL IMPORTANCE-2

•DIFFUSION•OSMOSIS•OSMOTIC PRESSURE•DIALYSIS

DR.RITTU CHANDELJunior Resident Grant Medical College,Mumbai

Dr.Rittu Chandel

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DIFFUSION

•solute particles move from higher concentration to a lower concentration in order to bring a uniform concenteration throughout.

factors affecting diffusion:1.concentration of solute2.temperature3.mean moecular velocity

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The concentration of oxygen molecules isgreater outside the cellthan inside

So the oxygen moleculesdiffuse into the cell

factor affecting diffusion-lipid solubilities of substances.Dr.Rittu Chandel

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oxygen

carbon dioxide

pulmonarycapillary

alveolar membrane

↓

factors affecting diffusion-partial pressure gradient,surface area,thickness of membraneDr.Rittu Chandel

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TYPES OF DIFFUSION

1.SIMPLE

2.FACILITATED

NO ENERGY REQUIRED.

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why facilitated diffusion?

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confirmational change of carrier protein

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PING PONG MECHANISM

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FICK'S LAW OF DIFFUSION

• ds/dt = DAdc/dx

• ds/dt = rate of movement of solutes

• D = diffusion constant

• A = area

• dc/dx = concentration gradient

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FACTORS AFFECTING DIFFUSION

• concentration gradient• electrical gradient of ionized solutes• pressure gradient of gases• mean molecular velocity • temperature• solubility• viscosity• size and shape of solute• pore size of membrane• time taken by diffusion is directly proportional to the square of

the distance traversed

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ELECTROCHEMICAL GRADIENT

conc of negative ions is more on left sides these charges diffuse to right side

•electric field is applied when there are equal no. of negative charges on both side

thus electric gradient created

concentration difference arises

electrical difference also present

concentration difference rises high enough to balance the two effectsDr.Rittu Chandel

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BIOMEDICAL IMPORTANCE

• respiratory exchange of gases

• intestinal absorption of pentoses

• limitation of cell size

• keratinized epidermis minimizes loss of water

• pneumonia,emphysema,panting and hyperapnea

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DIFFUSION TRAPPING

• salicylic acid and phenobarbital are excreted passively in distal tubule and collecting duct of kidney by diffusion trapping

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OSMOSIS • the net diffusion of solvent molecules from a

dilute to concentrated solution,when seperated by semipermeable membrane.

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OSMOTIC PRESSURE (¶)

hydrostatic pressure which exactly balances the osmotic influx

colligative property

the osmotic pressure exerted by particles in a solute is determined by the number of particles and not the mass of particles

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van't HOFFS LAWS

• the osmotic pressure is directly proportinal to the molar concentration of the solute,temperature remaining constant.

• the osmotic pressure is directly proportional to the temperature ,as long as its concentration remains constant

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BIOMEDICAL IMPORTANCE

hypotonichypertonicisotonic

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BIOMEDICAL IMPORTANCE

• osmotic distension of RBC

• kwashiorkar,nephrotic syndrome,severe vomiting

• edema in lymphoma

• polyuria in diabetes

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OSMOLE

• to express the concentration of solution in terms of number of particles,the unit osmole is used.

• 1 osmole = 1 gram molecular weight of undissolved solute.

• 180 g glucose = 1 g molecular wt.of glucose• =1 osmole• NaCl dissolves into two- Na and Cl• 58.5 g NaCl =2 osmole• 1/1000 osmole = 1 milliosmole

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OSMOLARITY AND OSMOLALITY

• OSMOLARITY-a solution that has 1 osmole of solute dissolved in each litre of solution.

• OSMOLALITY- a solution that has 1 osmole of solute dissolved in each kilogram of solution.

• difference between osmolarity and osmolality is less than 1%.

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RELATION OF OSMOLALITY TO OSMOTIC PRESSURE

• AT NORMAL TEMPERATURE,• 1 osmole/Kg 19300 mmHg• 1 milliosmole/Kg 19.3 mmHgnormal osmolality of ECF- 300 mOsm/Kg and ICFmultiplying on both sides by 300,to obtain osmotic pressure of

body fluid 1*300 =19.3*300 = 5790 mmHg approximately 5500 mmHgosmotic pressure of body fluid is .93 times calculated value.

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REVERSE OSMOSIS

application-purify water (to remove impurities) to concentrate fruit juices in wine industies to form whey protein powder

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DIALYSIS

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HEMODIALYSIS

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PERITONIAL DIALYSIS

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•BIOMEDICAL IMPORTANCE

• seperate proteins in pure form from the mixture with salts

• stopping enzymatic or metabolic reactions by removing small cofactor molecules from cell extract

• artificial kidney

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BIBLOGRAPHY

• TEXTBOOK OF MEDICAL PHYSIOLOGY-GUYTON (10th edition)

• TEXTBOOK OF MEDICAL BIOCHEMISTRY-RANA SHINDE (8th edition)

• BIOPHYSICS-DEBJYOTI DAS• MARK'S MEDICAL BIOCHEMISTRY• LEHNINGER• CELL AND MOLECULAR BIOLOGY• INTERNET

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THANK

YOU

Dr.Rittu Chandel