Physiology of cell membrane and membrane transport...“The cell membrane is a barrier ” Chemical...
Transcript of Physiology of cell membrane and membrane transport...“The cell membrane is a barrier ” Chemical...
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Physiology of cell membraneand membrane transport
Putcharawipa Maneesai, PhD.
Department of Physiology, Faculty of medicine, KKU
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Objectives
1. การจดัระบบ การเรียงตวัของโมเลกลุของไขมนัและโปรตีนในเย่ือหุม้เซลล์2. กระบวนการขนสง่ผา่นเย่ือหุม้เซลล์3. การแพร่4. ความดนัออสโมซิสและกระบวนการเกิดออสโมซิส5. ปัจจยัท่ีมีผลตอ่การขนสง่สารผ่านเย่ือหุม้เซลล์
นักศึกษาสามารถอธิบาย
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Structure of Plasma Membrane
Protein
Carbohydrate
Lipids
Integral protein: ˷70% Peripheral protein
Phospholipids Cholesterol Glycolipids
+ protein-> glycoprotein + lipid -> glycolipid
Receptors, channels, enzymes, transporters
Antigen, receptorImage from Purves et al., Life: The Science of Biology, 4th Edition
Singer & Nicholson, 1972Fluid mosaic model
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Properties of cell membrane
Selectively permeable/ semipermeable
Cell-cell recognition
Cell-cell communication
Selective permeability restricts materials based on:
• Size• Electrical charge• Molecular shape• Lipid solubility
“The cell membrane is a barrier”
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Chemical compositions of extracellular and intracellular fluids
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Cell membrane transport
1. Passive transport (diffusion)1.1 Simple diffusion1.2 Facilitated diffusion 1.3 Osmosis
2. Active transport 2.1 Primary active transport2.2 Secondary active transport 2.3 Endocytosis & exocytosis
Mechanism of transport
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1.1 Simple diffusion
A B
High concentration Low concentration
- Selective permeability- Gating: Voltage gating, Chemical or ligand gating
Protein channel : water and ions
Simple diffusion is the movement of molecules from one location to another by random thermal motion
Lipid bilayer : gases and ethanol
ความเขม้ขน้เท่ากนัจุดสมดุล = หยุดแพร่
“การแพร่แบบธรรมดา”
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Permeability of lipid membranes
Selective permeability restricts materials based on:
• Size• Electrical charge• Molecular shape• Lipid solubility
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**Carriers proteins
1.2 Facilitated diffusion
2. A conformational change occurs in the carrier protein
1. A molecule binds to the specific receptor
High concentration Low concentration“การแพร่แบบอาศัยตัวพา”
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Simple diffusion vs Facilitated diffusion
อตัราการแพรอ่าจถกูยบัยัง้แบบแก่งแย่ง (competitive inhibition) โดยสารท่ีมีโครงสรา้งทางเคมีคลา้ยกนั
อตัราการแพรแ่ปรเป็นสดัส่วนโดยตรงกบัความเขม้ขน้ของสารมจุีดอิม่ตัว
มีความจ าเพาะในการเคลื่อนยา้ยสารท่ีมีโครงสรา้งเคมีแบบใดแบบหนึ่งเท่านัน้
อตัราการแพรเ่รว็กว่าการแพรแ่บบธรรมดา
Facilitated diffusion
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Factor effecting rate of diffusion
Fick’s law of diffusion
J = Net molar diffusion (mmol/sec)P = permeability (cm/sec)A = surface area (cm2)C1 = Concentration in solution 1 (mmol/L)C2 = Concentration in solution 2 (mmol/L)
J = -PA (C1-C2)
** when C1=C2
Equilibrium
Permeability
Surface area
when
Concentration difference
Electrical potential
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Factor effecting rate of diffusion
Temperature Higher temperature Diffuse faster
Surface area Large surface Diffuse faster
Concentration Gradient
Higher gradient Diffuse faster
Size of particles Smaller particles Diffuse faster
Diffusion Medium Solid SlowestLiquid FasterGas Fastest
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1.3 Osmosis
Osmotic pressure (π)is the force of a concentration
gradient of waterPressure
required to stop osmosis
Low concentrationHigh concentration
Osmosis is the movement of water across the cell membrane
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Osmosis
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Osmotic Pressure (π) Calculation
π =iMRTwhere
π = osmotic pressurei = van't Hoff factorM = molar concentration of dissolved species (units of mol/L)R = the ideal gas constant (0.08206 L atm mol-1 K-1, or other
values depending on the pressure units)T = the temperature on the Kelvin scale
Morse equation
van't Hoff factor
ionic compounds dissolved in water, the van 't Hoff factor is equal to the number of discrete ions in a formula unit of the substance.
non-electrolytes dissolved in water, the van 't Hoff factor is essentially 1.
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Osmolality
Osmolality: the number of particles in the solution
mole = grams molecular weight
Molarity = mole of solutevolume of solution in liter
Osmolarity = 1 osmole of solute dissolved in each liter of water
Osmolality = 1 osmole of solute dissolved in each kilogram of water
Normal osmolality of ICF and ECF = 285 mOsm/L or ~300 mOsm/L
Osmole = number of particles (mole) in the solution
1 mole of solute particle =1 osmole
Ex: glucoseNon-dissociated solute
Dissociated solute 1 mole = > 1 osmoleEx: NaCl
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Tonicity
3 classifications of tonicity: 1. Isotonic2. Hypertonic 3. Hypotonic
12 3
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2. Active transport
สามารถขนส่งสารต้าน concentration gradient/ electrochemical gradient
High concentrationLow concentration
มจุีดอิม่ตัวของอัตราการขนส่ง
มคีวามจ าเพาะในการขนส่งสารบางชนิดและมีการยับยัง้แบบแก่งแย่งจากสารเคมทีีม่โีครงสร้างคล้ายกัน
ถูกยับยัง้โดยสารเคมหีรือกระบวนการใดๆทีห่ยุดการสร้างพลังงานจากเมแทบอลิซมึของเซลล์
1. Primary Active transport 2. Secondary Active transport
การขนส่งสารทีอ่าศัยพลังงานจากเมแทบอลิซมึของเซลลโ์ดยตรง การขนส่งสารทีอ่าศัยพลังงานโดยทางอ้อม
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2.1 Primary active transport
Energy
Energy is derived directly from
breakdown of ATP or some other
high-energy phosphate compound
Sodium potassium pump or Na, K ATPase
Animation: https://www.meduhub.com
Example : Na+-K+ ATPase pump to maintain the cell potential
: Ca2+-ATPase pump: muscle cells: H +-ATPase pump: gastric parietal cells
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Na+-K+-ATPase pump inhibitor
Ouabain is a cardiac glycoside that acts by inhibiting the Na+/K+-ATPase pump
Ouabain binds to ouabain binding site
increase of intracellular sodium
reduces the activity of the sodium-calcium exchanger (NCX)
elevates intracellular calcium
increase cardiac contractility increase in cardiac vagal tone cardiac arrhythmias
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2.2 Secondary active transport
Na+ /glucose-cotransporters
Na+
cotransport or symportEX: Na+-glucose or Na+-amino acid
:intestinal tract, renal tubule
counter transport or antiportEX: Na+-Ca2+ ; all cell membrane
: Na+-H+; proximal tubule of renal
important mechanism in transporting glucose across renal and intestinal epithelial cells
Energy is derived secondarily from energy stored in the form of ionic concentration differences of secondary molecular or ionic substances between the 2 sides of a cell membrane
1 2
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Co-transport and Counter transport
antiport
symport
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2.3 Membrane transport of macromolecule
Vesicular transport
- pinocytosis - phagocytosis - receptor-mediated endocytosis
Exocytosis
Endocytosis
https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBooktransp.html
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Endocytosis
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Movement of solutes across a typical plasma membrane involving membrane proteins
Direction of net flux across plasma membrane
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Resources
Widmaier, E. P., Raff, H., Strang, K. T., & Vander, A. J. (2014). Vander's Human Physiology: The Mechanisms Of Body Function.
Boston, Mcgraw-hill Higher Education.
Hall, J. E., & Guyton, A. C. (2011). Guyton And Hall Textbook Of Medical Physiology. Philadelphia, PA, Saunders Elsevier.
Barrett, K. E., & Ganong, W. F. (2012). Ganong's Review Of Medical Physiology. New York, Mcgraw-hill Medical.
e-learning KKU.
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ปฏบิัตกิาร Membrane Transport
เขา้เรยีนใหต้รงเวลา มี Pre-test ดว้ยนะคะ** อา่นคูมื่อปฏิบตัิการก่อนเขา้เรยีน