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In the name of God

1- membrane transport 2-osmosis M.Bayat PhD

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Session 1

Cell membrane lipid bilayer (1925)RBC fluid mosaic model

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Flip.flop Motion in lipid and pr

Types of motionsLaterallyRotation Flip,flop

cell membrane • It is composed of proteins and lipids proteins, 55 % phospholipids, 25 % cholesterol, 13 % other lipids, 4 % carbohydrates, 3 %• Lipid Barrier of the Cell Membrane Impedes Water

Penetration.

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phospholipids, 25 %

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Control of fluidity by cholesterol?

6*Involved in signal transduction.

Asymmetry in lipid distribution ?

Integral and peripheral pr

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Cell Membrane Proteins.• Membrane of myelinated axon 25%, membrane of mitochondria 75%• Mean: 55%

• integral proteins (intrinsic)

• Channels (or pores)• transporter• enzymes• Receptors• Structural• Pump

• peripheral proteins (extrinsic) Associate with the surface of the phospholipids' bilayer and predominantly by charge

interactions with integral proteins

• Enzymes• controllers of transport of substances through the cell membrane "pores."

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Transport across the Cell Membrane

Macromolecule transport : Material may cross membranes without passing through the molecules that make up the membrane

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Endocytosis

Exocytosis

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Very large particles enter the cell by a specializedFunction of the cell membrane called endocytosis.The principal forms of endocytosis are pinocytosis andphagocytosis. Pinocytosis means ingestion of macromolecules,such as most protein molecules that form vesicles of extracellular fluid. vesicle size is 100 to 200 nanometers

Phagocytosis means ingestion of large particles,such as bacteria ,whole cells,or portions of degenerating tissue.

ATP

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ca

ATP

Ca

Ingestion by the Cell - Endocytosis

The transport of molecules through membranes by diffusion, and Protein-mediated transport processes

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Carrier mediated transportCarrier mediated diffusion = facilitated diffusion

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Molecular transport from membrane

Reflection coefficient

Brownian motion.

Simple diffusion

Fick's first law of diffusion states the following:

√MW and Radius Lipid solubility

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20 mg/L

10 mg/L

A B

If concentration of the substance in chamber A doubles the diffusion ofThe substance will change from 10 mg/h to:

simple diffusion from channel

Facilitated diffusion by carrier pr

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Uniporters

symporters

antiporters

brings glucose into the cell (GLUT2)

facilitated diffusion

Saturation specificity Inhibition

Primary active transport (Pump) Primary active transport (Pump)

Na/K ATPase in all the cellsH ATPase Gastric parietal cells Renal distal tubules Ca ATPase

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Na/K pump & proton pump

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/cotransport__symport_and_antiport_.html

https://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio05.swf::Proton%20Pump

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P

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Na attachment = phosphorylationK attachment = Dephosphorylation

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The pump, while binding ATP, binds 3 intracellular Na+ ions.ATP is hydrolyzed, leading to phosphorylation of the pump at a highly conserved aspartate residue and subsequent release of ADP.A conformational change in the pump exposes the Na+ ions to the outside.  The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released. The pump binds 2 extracellular K+ ions. This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell.  The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released. ATP binds, and the process starts again.

  

Inactivation of the sodium-potassium pump will cause :

1. An increase in the intracellular volume2. increase intracellular Na 3. Decrease intracellular K4. Depolarize the membrane5. inactivation of Na channel6. decrease excitability

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Secondary active transport(co transport)

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Team work

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Osmosis

M.BayatPh.D

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Water diffusion

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Water osmosis

Water Net diffusion = 0

osmotic

1 milliosmole per liter concentrationis = 19.3 mm Hg osmotic pressure.

osmotic ally Active particle10 6

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Osm=c × n × QC= molar concentrationN=number of particle Q= osmotic coefficient

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Calculation of Osmolarity

100 mmol CaCl2 100 ×3= 300 mosm150 mmol NaCl 150 × 2= 300 mosm

280 mosm = iso-osmolar < 280 =hypo-osmolar >280 = hyper-osmolar

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osmotic coefficient × 19.3 ×

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Iso-osmolar =300 Hyper-osmolar >300 Hypo-osmolar <300

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osmotic equilibrium?

Tonicity

Mannnitol

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H2OMannnitol

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1.Which of the following is highly soluble in lipids: A.O2 B.N C. CO2 D. alcohol E. all 2.Which of the following enters the cell through protein channels: A. water B.O2 C.Na D. a&c3.Which of the following enters the cell through carrier mediated

diffusion: A.AA B.glucose C:hormones D: all4. What is difference between primary active transport and

secondary active transport? • Glucose is cotransported into cell with………ion • Cell cytosol concentration of calcium is …………times lower

than outside• The location of Calcium pump in …….,……..,……..

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