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1、General Functions of Cells,Xiaoqun Qin, PhD.,MD.,Cellular Basic of Physiologic Function,Part : The Functions of Cell Membrane,Essential role of cell membrane:,Action of outpost Exchange of material Accept signal Distinguish mark Programming reactions,C,D,Model of simple diffusion,D = kC,Facilitated
2、diffusion,1.Conception: the substances which are insoluble in lipids pass through the cell membrane with its grade by the help of membrane proteins. 2.Character: with grade; specific ;adjustable . 3.Types: (1)channel mediated diffusion: receptor operated; voltage gated ; mechanic gated. (2)carrier m
3、ediated diffusion: specific, saturable,competitive.,Active transport,Character: using ATP; against the grade. Significance: reserving potential; protect cell from swollen.,2 K+,3 Na+,ATP ADP+Pi,Characteristics of the Transport by Na+ pump,Directional transport Coupling process ATP is directly requir
4、ed Electrogenic process,Importance of the Na+-K+ Pump,Maintain high intracellular K+ concentration gradients across the membrane. Control cell volume and phase Maintain normal pH inside cell Develop and Maintain Na+ and K+ concentration gradients across the membrane Electrogenic action influences me
5、mbrane potential Provides energy for secondary active transport,Secondary Active Transport,Coupled transport. Energy needed for “uphill” movement obtained from “downhill” transport of Na+. Hydrolysis of ATP by Na+/K+ pump required indirectly to maintain Na+ gradient.,Secondary active transport,Na+,g
6、lucose,Na+,H+,out in,out in,co-transport counter-transport (symport) (antiport),Co-transporters will move one moiety, e.g. glucose, in the same direction as the Na+.,Counter-transporters will move one moiety, e.g. H+, in the opposite direction to the Na+.,Out side higher potassium and lower glucose,
7、Inside lower potassium and higher glucose,Bulk Transport (Endocytosis and Excytosis),Movement of many large molecules, that cannot be transported by carriers. Exocytosis: A process in which some large particles move from inside to outside of the cell by a specialized function of the cell membrane En
8、docytosis: Exocytosis in reverse. Specific molecules can be taken into the cell because of the interaction of the molecule and protein receptor.,Exocytosis Vesicle containing the secretory protein fuses with plasma membrane, to remove contents from cell.,Endocytosis Material enters the cell through
9、the plasma membrane within vesicles.,Types of Endocytosis,Phagocytosis - (“cellular eating”) cell engulfs a particle and packages it with a food vacuole. Pinocytosis (“cellular drinking”) cell gulps droplets of fluid by forming tiny vesicles. (unspecific) Receptor-Mediated binding of external molecu
10、les to specific receptor proteins in the plasma membrane. (specific),Example of Receptor-Mediated Endocytosis in human cells,The pathway of signal transduction across membrane,Receptor-gated channel Receptor-GTP binding protein-effecter enzyme system: CAcAMP; CG cGMP; PLC IP3,DG Tyrosine protein kin
11、ase (TPK) receptor,Signal across membrane transduction based on the receptor-G protein-effect enzyme system and induction of the second messages.,Part : Cellular Bioelectricity,Conception about stimulus and excitability,Excitation: an action potential occurs after a effective stimulus acting on cell
12、. Excitability: cells ability to genesis action potential after being stimulated. Excitable cells: cells which are easy to genesis action potential under stimulus. Essential element of stimulus: intensity ,duration,changing rate.,P,P0,T0,T,Intensity-duration curve,Threshold stimulus,Measurement of c
13、ell bioelectricity:,Extracellular record; Microelectrode and Intracellular record; Voltage clamp and patch clamp,Cole and colleagues developed a method for maintaining Vm at any desired voltage level (FBA, Feedback Amplifier) Required monitoring voltage changes, feeding it through an amplifier to dr
14、ive current into or out of the cell to dynamically maintain the voltage while recording the current required to do so,The voltage clamp,INa=GNa(Em-ENa),Cytoplasm,Ion channels,“Giga-seal“,Glass,microelectrode,Suction,1 m,Patch clamp recording,Cell Membrane,100 ms,4 pA,Closed,Open,Single channel recor
15、d,Describing words for cell bioelectricity:,Trans-membrane potential: including resting potential, polarization, hyperpolarization, depolarization, repolarization Trans-membrane current: inward current, outward current Character of channels: membrane resistance and conductance depend upon the number
16、 of open channels. G=1/R (unit: Siemens,S) the voltage-dependent functional states of channels. all or none feature in a single channel opening and integrated behave of all collected channels.,Resting Potential (RP),RP: difference of potentials between both sides of the membrane in resting state.,Mechanism of RP formation: (1) unequal distribut
