生理学的概念及生命活动的特征 (4).ppt

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1、PhysiologyY O U C A N C L I C K H E R E T O A D D Y O U R T E X TActive TransportActive Transportn When a cell membrane moves molecules or ions uphill against a concentration gradient(or uphill against an electrical or pressure gradient),the process is called active transport.Active TransportSome ex

2、amplesn sodium,potassium,calcium,iron,hydrogen,chloride,iodiden urate ions,several different sugarsn most of the amino acids4Primary active transport Active transport Secondary active transport Vesicular transport51 Primary active transportPrimary active transportCharacteristics:n occurs against an

3、electrochemical gradient(“uphill”).n requires direct input of metabolic energy in the form of adenosine triphosphate(ATP)and therefore is active.n is carrier-mediated and therefore exhibits stereospecificity,saturation,and competition.Primary active transportExamplesa.Na+,K+-ATPase(or Na+K+pump)b.Ca

4、2+-ATPase(or Ca2+pump)c.H+,K+-ATPase(or proton pump)Na+,K+-ATPase(or Na+K+pump)Function：Na+,K+-ATPase(or Na+K+pump)in cell membranes transports Na+from intracellular to extracellular fluid and K+from extracellular to intracellular fluid;it maintains lowintracellular Na+and high intracellular K+.Post

5、ulated mechanism of the sodium-potassium pump.ADP,Adenosine diphosphate;ATP,adenosine triphosphate;Pi,phosphateion.Na+,K+-ATPase(or Na+K+pump)Characteristics:Both Na+and K+are transported against their electrochemical gradients.Energy is provided from the terminal phosphate bond of ATP.The usual sto

6、ichiometry is 3 Na+/2 K+.Specific inhibitors of Na+,K+-ATPase are the cardiac glycoside drugs ouabain and digitalis.Ca2+-ATPase(or Ca2+pump)FunctionIt transports Ca2+against an electrochemical gradient in the sarcoplasmic reticulum(SR)or cell membranesSarcoplasmic and endoplasmic reticulum Ca2+-ATPa

7、se is called SERCA.H+,K+-ATPase(or proton pump)Primary active transport of hydrogen ions is especiallyimportant at two places in the body:(1)in the gastric glands of the stomach(2)in the late distal tubules and cortical collecting ducts of the kidneys.It is inhibited by proton pump inhibitors,such a

8、s omeprazole2Secondary active transportUnder appropriate conditions,this diffusion energy of sodium can pull other substances along with the sodium through the cell membrane.Secondary active transportCharacteristics:a.The transport of two or more solutes is coupled.b.One of the solutes(usually Na+)i

9、s transported“downhill”and provides energy for the“uphill”transport of the other solute(s).Secondary active transportCharacteristics:c.Metabolic energy is not provided directly,but indirectly from the Na+gradient that is maintained across cell membranes.Thus,inhibition of Na+,K+-ATPase will decrease

10、 transport of Na+out of the cell,decrease the transmembrane Na+gradient,and eventually inhibit secondary active transport.Secondary active transportCharacteristics:d.If the solutes move in the same direction across the cell membrane,it is called cotransport,or symport.Secondary active transportExamp

11、les:n Na+glucose cotransport in the small intestine n Na+K+2Cl cotransport in the renal thick ascending limb.Secondary active transportNa+glucose cotransport(symport)in intestinal or proximal tubule epithelial cell.Characteristics:e.If the solutes move in opposite directions across the cell membrane

12、s,it is called countertransport,exchange,or antiport.Secondary active transportExamples:n Na+Ca2+exchange n Na+H+exchangeSecondary active transportNa+Ca+countertransport(antiport).3Vesicular transportVesicular transportFunction:Transport macromolecules and particulate matterClassification:nExocytosis nEndocytosis细Thank you