Ion pump

One of membrane transport proteins

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Ion pump is Membrane transporter one of. It is also regarded as a special kind of Carrier protein , can drive specific ions to reverse Electrochemical gradient go through plasma membrane , consumed at the same time ATP Formed energy, belonging to Active transportation 。 The essence of ion pump is External energy Driven reversibility ATPase 。 External energy can be electrochemical gradient energy, light energy, etc. The activated ion pump hydrolyzes ATP, and Hydrolysate Phosphate radical After binding, it will undergo self transformation, thus transferring ions from low concentration to high concentration, so that ATP chemical energy Electrochemical gradient energy for conversion into ions. There are many known ion pumps, each of which only transports specific ions. Intracellular ion pumps mainly include Sodium potassium pump 、 Calcium pump and proton pump 。

Chinese name: Ion pump

Mode of transportation: Active transportation
Main types: Sodium potassium pump, calcium pump and proton pump

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hypothesis

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The ion pump hypothesis is an explanation plasma membrane upper Active transportation An example of a mechanism. It believes that the transport of some ions can reverse concentration gradient The direction of Lipid bilayer Upper Intrinsic protein Of Molecular conformation It can be regarded as a special type of Carrier protein , can drive specific ions to reverse Electrochemical gradient The process of passing through the plasma membrane and simultaneously consuming ATP The formed energy belongs to active transportation.

Na-K pump

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Na-K pump exists on the plasma membrane of animals Cell plasma membrane No Na-K pump, it has two large and two small pumps Subunit ， Large subunit catalysis ATP hydrolysis ， Small subunit Is a glycoprotein 。 After the big subunit is combined with Na+in the form of pro Na+, hydrolysis is triggered ATP 。 The energy released by each ATP hydrolysis transmits 3 Na+ions to the extracellular space, and simultaneously absorbs 2 K+ions into the cell, resulting in transmembrane gradient and potential difference Nerve impulse conduction Especially important, the membrane potential difference caused by Na+- K+pumps accounts for about the whole Nerve membrane 80% of the voltage. If the purified Na+- K+pumps are assembled in the erythrocyte membrane vesicles（ Blood shadow ）On the other hand, artificially increase the Na+, K+gradients on both sides of the membrane to a certain extent, when the energy held by the gradient is greater than ATP hydrolysis Of chemical energy Na+, K+will flow through the Na+- K+pump in the reverse direction, and synthesize ATP at the same time. This reversible phenomenon is a universal property of ion pumps.

Ca ² +Pumps

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Ca ² +Pumps are distributed in dynamic plant cell plasma membrane 、 Mitochondrial intima 、 Endoplasmic reticulum SER like capsule organelle ）, Animals Muscle cell On the sarcoplasmic omentum, there are 1000 amino acid Formed by polypeptide chain of Transmembrane protein , which is Ca ² +Activated ATPase , each hydrolyzed ATP Transfer two Ca ² +To the outside of the cell to form calcium ion Gradient. usually cytoplasm Free Ca ² Γ Concentration is very low, about 10 – 7~10 – 8 mole /Liters, Intercellular fluid Ca ² +Concentration is high, about 5 × 10 – 3 mol/l. Extracellular Ca ² +Even a small amount of influx into the cell will cause Cytoplasm Free Ca ² +Significant change in concentration, resulting in a series of Physiological response 。 Calcium flow can rapidly transmit extracellular signals into cells, so Ca ² +is a very important signaling substance. Mitochondrial lumen Sarcoplasmic reticulum High concentration of Ca in endoplasmic reticulum like capsule ² +, concentration greater than 10 – 5 mol/l, named“ Calcium bank ”。 In certain Signal action Lower Ca ² +Release from calcium bank to cytoplasm for regulation Cell movement 、 Muscle contraction , growth, differentiation, etc physiological function 。

proton pump

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proton pump Namely, H+pumps include H+- ATP pumps and H+ inorganpyrophosphate Pump.

1. H+- ATP pump

stay plant cell Protoplasm membrane and Tonoplast There are many reasons ATPase Driven H+pumps, their main function is to adjust Protoplast To drive the absorption of anions and cations. from mitochondrion Generated ATP for plasma membrane The proton pump needs the energy released by ATP to establish the transmembrane proton gradient and Potential difference , proton gradient activation ion channel Or reverse transporter or Simultaneous transportation Device, regulating ion or dead Solute ingress and egress. The proton pump on the tonoplast pumps H+into vacuole ， Apoplast 、 Cytoplasmic sol And vacuoles, which are 5.5, 7.3~7.6 and 4.5~5.9 respectively.

2. H+- Pyrophosphoric acid pump

H⁺– inorganpyrophosphate The pump is a H+pump located on the tonoplast, which uses the free energy in pyrophosphoric acid (PPi) (rather than ATP ）, actively pump H+into the vacuole, resulting in the inside and outside of the membrane Electrochemical potential gradient , leading to the active trans membrane transport of nutrients.

Sputtering pumping mechanism

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Figure 5

As shown in Figure 5 physical process , which can be broken down into six steps for explanation.

Figure 5: Sputter ion pump Pumping mechanism Sketch Map

1) A in the figure indicates that under low pressure, when high voltage is applied between cathode and anode Field emission 。

2) In the figure, B represents the electronic operation under the action of electricity and magnetic field Spiral movement 。

3) C in the figure represents the electronic and Gas molecule collision produce Positive ion and Secondary electron , causing avalanche effect.

4) In the figure, D indicates that positive ions bombard the titanium cathode, sputtering titanium atoms fall on the anode cylinder, forming a fresh titanium film, and some fall on the periphery of the negative plate（ β Zone).

5) E in the figure represents active gas and fresh titanium Membrane reaction Forming compounds, chemical adsorption On the inner wall of anode cylinder. Sui gas is ionized and ions bombard under the action of electric field Cathode process Is discharged from. The elimination methods are: (1) Ions are directly injected into the cathode surface or β Area (a in the figure); Oblique projection The ions cut into the cathode surface, and the ions and titanium were removed and buried β Area (b in the figure); (2) The ions are not penetrated into the cathode, and an electron from the cathode is recovered to Neutral atom Or molecule, reflected to anode Internal surface Buried (c in the figure), which is called "charged energy" Neutral particle Reflection ".

6) F in the figure indicates that for hydrogen, due to its small mass, hydrogen ions bombard titanium The sputtering yield of the plate is very low, Hydrogen ion H ² +Or H+To Titanium plate And then diffuses into the lattice of titanium to form TiH Solid solution And is discharged. H in this solid solution at room temperature ² The concentration of+is 0.05%. When the temperature is higher than 250 ℃, hydrogen will be released again. Large amount of titanium Hydrogen absorption After. because Exothermic reaction When the temperature of the titanium plate rises to 250 ℃, in addition to releasing hydrogen again, the lattice of the titanium plate expands and cracks. It is usually necessary to increase the heat dissipation capacity of titanium plate to improve the hydrogen removal capacity of sputtering ion pump. To improve the hydrogen pumping speed, the titanium plate surface should be kept clean lattice constant Larger β- Ti or titanium alloy As cathode plate, or introduce argon content comparable to hydrogen. Due to the high sputtering yield of argon, the pumping speed of hydrogen can be increased.

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