Biophysics I - OSMOSIS 04/11/2014 · Biophysics I - OSMOSIS 04/11/2014 2 before after (3-4 hours)...

Biophysics I - OSMOSIS 04/11/2014

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OSMOSIS, MEMBRANETRANSPORT

Andrea Vig

University of Pécs, Medical School,

Department of Biophysics

28/10/2014

OVERVIEW – DIFFUSION BROWNIAN MOTION

random thermal motion of particles

DIFFUSION

due to the non-uniform (inhomogeneous) distribution of particles

net transport of particles (Brownian motion) occurs from a region of higher concentration to a region of lower

concentration which continues until the distribution of particles is uniform (homogeneous)

FICK’S 1st LAW (spatial description)

DIFFUSION COEFFICIENT: Stokes-Einstein equation

FICK’S 2nd LAW (spatial & temporal description)

𝑱 = −𝑫∆𝒄

∆𝒙

𝑫 =𝒌𝑻

𝟔𝝅𝜼𝒓

Onsager’s equation (linear, irreversible processes): J=XL The flow density of the extensive quantity (J)

is linearly proportional to the gradient of the intensive quantity (X)

∆𝑐

∆𝑡= 𝐷

∆(∆𝑐∆𝑥

)

∆𝑥


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before

after (3-4 hours)

Observation: the leaf of salad becomes bigger and looks fresh again

Experiment: place a dried leaf of salade into water

OSMOSIS IN THE KITCHEN

Osmosis in the k itchen.mp4

Experiment: place an egg into corn syrup then into water

CORN SYRUP WATER

Observation : the egg shrinks Observation: the shrinked egg gains its original

size, and it continues to get even bigger

before after before after

OSMOSIS

sugar solution

water before after

Experiment: fill a small-size semi-permeable bag with sugar dissolved in water, and placed in a

water filled container

Observation : the bag is swelling, the water surrounding

it remains pure, sugar solution has been diluted


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What is the difference between the „ink” experiment and the

„salade/egg/sugar” experiment?

NO TRANSPORT

1. SOLID (non-permeable) WALL (as Fick’s experiment)

OSMOSIS

x (distance)

fluid→gas (no complicated molecular interactions)

A+B components, we usually ignore one, and examine the distribution of

the other


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free DIFFUSION

both particles (smaller/larger) reach homogeneous distributions

2. NO WALL

OSMOSIS

x (distance)

t (tim

e)

restricted DIFFUSION: OSMOSISsmaller molecules reach a uniform distribution

larger molecules remain in the compartment

3. SPECIAL WALL

OSMOSIS


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SEMIPERMEABLE – „filter”allows smaller slovent molecules to pass through, but not the larger solute molecules

PORE DIAMETER SELECTIVITY

animal skin pellicles, walls of living cells, ceramic plate with holes, cellophane

3. SPECIAL WALL

OSMOSIS

semi-permeable membrane

OSMOSIS:

unidirectional matter flow, which takes place by means of

diffusion

semipermeable wall + concentration difference

(from the perspective of osmosis, the dissolved substance’s qualities are irrelevant)

type of the wall matter transport

yes: non-permeable no

no free diffusion

yes: SEMIPERMEABLE restricted diffusion: OSMOSIS

OSMOSIS –types of walls, summary


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QUANTIFICATION OF OSMOSIS

solvent

solvent

+ solute

mixturesemipermeable membrane

INJ

OUTJ

INJ

OUTJ

h

r: density

h: height

g = 10 m/s2

-concetration difference

-semipermeable membrane:allows solvent to pass through but

not the solute

-solvent flow throught the

semipermeable membrane

-the volume of the solvent +

solute mixture increases

HYDROSTATIC PRESSURE

(ph)

-solvent flow slows down

-dynamic equilibrium

OSMOTIC EQUILIBRIUM

semi-

permeable

membrane

sugar

solution

water

OSMOTIC PRESSURE

OSMOTIC PRESSURE pressure that has to be exerted on the solution connected to pure solvent by a

semipermeable membrane to reach dynamic equilibrium, to counteract osmosis

pressure that inhibits the net solvent flow

INJ

OUTJ

INJ

OUTJ


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for dilute solutions and perfect semipermeable membranes using the equation of state of

the ideal gas

V: volume

n: mole fraction

T: temperature

c: concentration

R: universal gas constant

VAN’T HOFF’s LAW

the osmotic pressure is linearly proportional to the concentration

OSMOTIC PRESSURE

𝒑osmotic = 𝒄𝑹𝑻

𝒑ozmózis~𝒄

p2=𝑛𝑏𝑙𝑢𝑒2

𝑉𝑅𝑇

1. 2.

nblue1=nblue2

pV=nRT

p1=𝑛𝑟𝑒𝑑+𝑛𝑏𝑙𝑢𝑒1

𝑉𝑅𝑇

p1-p2=posmosis=𝑛𝑟𝑒𝑑𝑉

𝑅𝑇

cred

upon OSMOSIS the net particle transport occurs from the low-

concentration regions (of the solute!!!!!) (low osmotic pressure) to

the high-concentration regions (high osmotic pressure)

from low osmotic pressure→high osmotic pressure

it is always the more dense solution which becomes diluted

solventsolvent

+ solute

mixture

OSMOSIS

OSMOTIC PRESSURE

1.

2.


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CLASSIFYING SOLUTIONS ON THE BASIS OF OSMOTIC PRESSURE

HYPERTONIC ISOTONIC HYPOTONIC

higher concentration

c > cxhigher osmotic pressure

p > px

same concentration

c = cxsame osmotic pressure

p = px

lower concentration

c < cxlower osmotic pressure

p < px

for the cells of the human body,

blood:

0.87 % (0.15 M) NaCl

physiologic saline solution

3.8 % sodium citrate

5.5 % (0.3 M) glucose

x: reference

HYPERTONIC

(more concentrated: 10% NaCl)

HYPOTONIC

(less concentrated: 0.01% NaCl)

ISOTONIC

(0.87 % NaCl)

net water OUTflux net water INflux

RED BLOOD CELLS IN DIFFERENT ENVIRONMENT

pout > pin pout = pin pout < pin

NO net water flux


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HYPERTONICHYPOTONIC IZOTONIC

RED BLOOD CELLS IN DIFFERENT ENVIRONMENT

net water OUTflux

PLASMOLYSIS

plasma membrane is pulled

away from the cell wall

net water INflux

TURGOR PRESSURE

plasma membrane is pushed to

the cell wall

Role of osmosis in the life of plant cells

PLANT CELLS IN DIFFERENT ENVIRONMENT

NO net water flux


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1. INJECTION, INFUSION

drugs are dissolved in physiological saline solution

isotonic environment (compared to the body fluid)

2. TREATMENT OF OEDEMAS, INFLAMED AREAS

abnormal accumulation of fluid beneath the skin or in one or more cavities

of the body that produces swelling (fluid accumulation)

dextran-solution/bitter salt (MgSO4-solution)-based treatment

hypertonic environment is created (compared to the swollen areas)

induces water outflow from the swollen areas

reduced swelling

3. TREATMENT OF CONSTIPATION - LAXATIVE SALTS

laxative salts are not absorbed by the large intestine

hypertonic environment is created in the large intestine

results in water influx into the large intestine

dilution of colonic content, facilitated excretion

OSMOSIS IN THE MEDICAL PRACTICE

hypertonic

water influx

hypertonic

water outflow

different particles can be sorted by semipermeable membranes

pore size of the membrane determines which molecules can pass

through the membrane

t = 0 s t

4. DIALYSIS

dialysis bag

semipermeable membrane

concentrated solution



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protein products

toxins

other waste products

treatment of patient with severe kidney disease

remove soluble chemicals toxic for the body (protein products, toxins, other waste

products exit with water, essential plasma proteins, cellular elements of blood

remain),

4.1. HAEMODIALYSIS

Schematic diagram of haemodialysis („artificial kidney” instrument).


essential element:long

semi-permeable membrane

(cellophane), surrounded

by dial.solution

average treatment time:

4-8 h

dial.solution has to be

changed frequently

check ion-concentrations

and metallic-ion-

contaminations in the solution

OVERVIEW

• Osmosis

• Van’t Hoff’s law

• Osmotic pressure and its significance (rbc, medical application)


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MEMBRANE STRUCTURE, MEMBRANETRANSPORT

MEMBRANE STRUCTURE

Phospholipids are the main components of biological membranes.

Biological membranes consists of lipids and proteins to bind with non-covalent bond.

Phospholipid = diglyceride (1 glycerole + 2 fatty acids) + phosphate group + organic molecule

(e.g. choline)


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Membrane-models

Lipid-soluble substances enter the cell quickly.

Benzine-lipid mixture, the evaporation of petrol amolecular lipid film is formed.

Petrol – soluble lipids form lipid bilayer on the surfaceof the water.

Transmembrane proteins.

The proteins are an integral part of cell membrane. Thelipid bilayer. Partly explains the proteins, sugars, ions and

other hydrophilic substances fast passage.

Discovery of Electronmicroscope.The cells are covered by plasmamembrane.„Unit-membrane”model.

Mosaic-like arrangement of

proteins in the membrane.

Dr. habil. Kőhidai László

Irving Langmuir was an American chemist and

physicist. 1932 – Nobel prize

Fats are arranged in a layer on the surface.

1972 „ Fluid mosaic” model

1925 Lipid bilayer

FLUID MOSAIC MODEL

Singer – Nicolson1972

Membrane of erythrocyte

http://www.youtube.com/watch?v=ZP3i5Q9XfTk

http://www.youtube.com/watch?v=oq4Um1oV4ag

http://osulibrary.oregonstate.edu/specialcollections/coll/pauling/blood/people/singer.html

http://osulibrary.oregonstate.edu/specialcollections/coll/pauling/blood/people/singer.html

http://www.youtube.com/watch?v=ZP3i5Q9XfTk


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STRUCTURE OF THE CELL MEMBRANE

MEMBRANE PROTEINS These proteins determine the function of the membranes.

The types of membrane proteins:

Transmembrane proteins – It can bind to the hydrophobic part of the

membrane.

Peripheral membrane proteins– not directly linked to the membrane.

Glycoproteins - these oligosaccharides are attached to the extracellular side of

the membrane proteins.

Glycosyl-phosphatidylinositol (GPI) - are covalently bonded to the

membrane’s lipids.

Roles:

Ion channels

Receptors

Signal transduction


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EXTRACELLULAR

SPACE

Example 1: DIFFUSION THROUGHT THE CELL MEMBRANE

INTRACELLULAR SPACE

cytoplasm

water

apolar molecules

ions

monosaccharides

amino acids

metabolites

different mechanism: exocytosis and endocytosis

MATTER

TRANSPORT

LIPID BILAYER

MEMBRANE PROTEINS

PASSIVE DIFFUSION

ion channels carrier proteins carrier proteins

WITHOUT MEDIATOR WITH MEDIATOR

PASSIVE TRANSPORT ACTIVE TRANSPORT

FACILITATED DIFFUSION

DIFFUSION THROUGH THE CELL MEMBRANE

I. TRANSPORT MECHANISM

II. ENERGETIC REQUIREMENTS

TRANSPORT PROCESSES ACROSS BIOLOGICAL MEMBRANES

1. 2. 3. 4.


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1. PASSIVE DIFFUSION

Passive transport

Without mediator

direction of transport:ELECTRO-CHEMICAL POTENTIAL GRADIENT

chemical potential gradient (concentration)

electric potential gradient (charge)

rate of diffusion: Fick’s laws

mediator: no

energetic requirement: no

examples:

hydrophobic molecules: O2, N2

small polar molecules: CO2, water, alcohol, urea, glycerol

glucose, sacharose


2. FACILITATED DIFFUSION

Passive transport

With mediator: ION-CHANNEL

direction of transport: chemical or electro-chemical potential gradient

rate of diffusion: faster than that expected from Fick’s laws

mediator: ION-CHANNEL PROTEIN

transmembrane proteins

closed / open state: no transport / transport

regulation:

mechanically-gated (mechanical tension)

voltage-gated (potential difference)

ligand-gated (ligand-binding)

selectivity: size & charge of the ions




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Passive transport

With mediator: CARRIER PROTEINS

direction of transport: chemical or electro-chemical potential gradient

rate of diffusion: faster than that expected from Fick’s laws

mediator: CARRIER PROTEIN

specifically binds the ions or molecules and promotes their transport




Active transport

With mediator: CARRIER PROTEINS

direction of transport: AGAINST the chemical or electro-chemical potential gradient

! ENERGY IS REQUIRED

mediator: CARRIER PROTEIN

uniporter

symporter/antiporter

energetic requirement: yes

ATPase transporter (ATP hydrolysis)

photo transporter (light energy)

coupled transporter (energy from an other transport)

example: Na+-K+ pump


Biophysics I - OSMOSIS 04/11/2014 · Biophysics I - OSMOSIS 04/11/2014 2 before after (3-4 hours)...

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