The document discusses the principles of diffusion in biological systems, explaining its definition, types, and significance, particularly in drug release and distribution. It covers Fick's laws of diffusion, which detail the relationship between diffusion flux and concentration gradients, noting key differences between passive, facilitated, and active diffusion. Overall, the content highlights how diffusion processes are critical to various biological and pharmaceutical applications.

1. SOLUBILITY – 4
DIFFUSION PRINCIPLES IN
BIOLOGICAL SYSTEMS
Presented By:
Mr. S.M. Ambore
Asst. Professor,
DK Patil Institute of Pharmacy, Loha. Nanded

2. LEARNING OUTCOMES….
Diffusion
Diffusion Flux
Concentration gradient
Diffusion Laws 2

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DIFFUSION
Diffusion is defined as a mass transfer of
individual molecules of substance caused by
random molecular motion and associated with
concentration gradient.
OR
A physical process that refers to the net
movement of molecules from a region of high
concentration to lower concentration under the
influence of concentration gradient.
1. It is time dependant process.
2. It is well explained by FICK’S LAW OF DIFFUSION

4. DIFFUSION
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5. DIFFUSION
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NEED OF DIFFUSION
It helps to understand,
1. Release of drug from Pharmaceutical dosage form
2. Ultrafiltration, microfiltration, dialysis,
hemodailysis.
3. Permeation & distribution of drug in living tissues.
4. Estimation of molecular weight of polymers.
5. Prediction of absorption & elimination of drug.

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TYPES OF DIFFUSION
PASSIVE DIFFUSION:
1. Net movement of material from an area of high
concentration to lower concentration area.
2. The difference between high & low concentration
is called as concentration gradient.
3. Diffusion will continue until the gradient has been
eliminated or equilibrium is attained.

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TYPES OF DIFFUSION
FACILITATED DIFFUSION:
It is movement of molecules across th cell
membrane via special transport proteins that are
embedded within the cellular membrane
ACTIVE DIFFUSION:
It is movement of molecules across membrane
from lower conc. to higher conc. against
concentration gradient.

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11. DIFFUSION FLUX
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How many atoms moving at how much time in how much
area is called Flux(J).
The Diffusion Flux(J) is the amount of matter flowing
through a unit area in unit time.
It is denoted by J.

12. CONENTRATION GRADIENT
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1. Rate of change of concentration per unit change of
position.
2. It is denoted by dc/dx.

13. LAWS OF DIFFUSION
1. FICK’s FIRST LAW OF DIFFUSION
2. FICK’s SECOND LAW OF DIFFUSION
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14. FICK’S FIRST LAW OF DIFFUSION
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This law describes the rate at which diffusion occurs.
This law states that the diffusion flux is directly
proportional to the concentration gradient.
J α dc/dx
J = -D dc/dx
Where,
J – Flux
dc/dx – Concentration gradient
D -- Diffusion coefficient or diffusivity.

15. FICK’S FIRST LAW OF DIFFUSION
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J α dc/dx
J = -D dc/dx
Negative sign indicates that flow occurs from
higher concentration to lower concentration.
The flux is independent of time.

16. FICK’S SECOND LAW OF DIFFUSION
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Change in concentration with time in a
particular region is proportional to the change in
concentration gradient at that point in the system.
dc/dx = - dJ/dx
This is extension of First Fick’s Law
Diffusion flux(J) is function of both space and time.

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