主动运输和组易位之间的差异

Key Difference – Active Transport vs Group Translocation

Molecules pass in and out from the cells via细胞膜。细胞膜是一种控制分子运动的选择性渗透膜。分子自然地从较高的浓度转移到浓度梯度较低的浓度。它是被动的，没有能量输入。但是，在某些情况下，分子在浓度梯度上穿越膜，从较低的浓度到较高的浓度。此过程需要一个能量输入，称为主动运输。组易位是另一种主动转运形式，其中某些分子使用源自phosphorylation。The key difference between active transport and group translocation is thatin active transport,substances are not chemically modified during the movement across the membrane尽管，in group, translocation substances are chemically modified.

内容
1.Overview and Key Difference
2.What is Active Transport
3.What is Group Translocation
4.Side by Side Comparison – Active Transport vs Group Translocation
5.概括

什么是主动运输？

Active transport is a method of transportingmolecules通过利用从ATP水解。在许多情况下，细胞需要某些物质，例如离子，glucose,amino acids, etc. at higher or proper concentrations. In these occasions, active transport carries substances from a lower concentration to a higher concentration against the concentration gradient utilizing energy and accumulates inside the cells. Therefore, this process is always associated with a spontaneous exergonic reaction such as ATP hydrolysis, which provides energy to work against the positiveGibbs energy运输过程。

主动运输可以分为两种形式：primary active transport and secondary active transport。Primary active transport is driven using the chemical energy derived from ATP. Secondary active transport uses potential energy derived from the electrochemical gradient.

Specific transmembranecarrier proteins and channel proteins促进主动运输。主动运输过程取决于膜的载体或孔蛋白的构象变化。例如，当钾离子和钠离子分别通过主动转运分别输入和流入细胞时，钠离子泵显示出反复的构象变化。

There are many primary and secondary active transporters in the cell membranes. Among them, sodium-potassium pump, calcium pump, proton pump, ABC transporter and glucose symporter are some examples.

What is Group Translocation?

Group translocation is another form of active transport in which substances are subjected to covalent modification during the movement across the membrane.磷酸化is the main modification undergone by transported substances. During phosphorylation, a phosphate group is transferred from one molecule to another. Phosphate groups are joined by high energy bonds. Hence, when a phosphate bond breaks, a relatively large amount of energy is released and is used for the active transport. Phosphate groups are added to the molecules which enter the cell. Once they cross the cell membrane, they are returned to the unmodified form.

PEP磷酸转移酶系统是细菌摄入糖摄取的组易位的一个很好的例子。通过该系统，将糖分子（例如葡萄糖，甘露糖和果糖）转运到细胞中，同时被化学修饰。进入细胞时，糖分子被磷酸化。PEP提供了能量和磷酸基。

What is the difference between Active Transport and Group Translocation?

主动运输vs Transloca组tion
Active transport is the movement of ions or molecules through a semipermeable membrane from a lower concentration to a higher concentration, consuming energy.	Group translocation is an active transport mechanism in which molecules are chemically modified during the movement across the membrane.
化学修饰
Molecules are not normally modified during the transportation.	分子在组易位期间被磷酸化并化学修饰。
Examples
钠钾离子泵是主动运输的一个很好的例子。	PEP phosphotransferase system in bacteria is a good example for group translocation.

概括– Active Transport vs Group Translocation

The cell membrane is a selectively permeable barrier, which facilitates the passage of ions and molecules. Molecules move from a high concentration to a low concentration along the concentration gradient. When the molecules are required to travel from a lower concentration to a higher concentration against the concentration gradient, it is necessary to provide an energy input. The movement of ions or molecules across a semipermeable membrane against the concentration gradient with the aid of proteins and energy is known as active transport. Group translocation is a kind of active transport which transports molecules after being chemically modified. This is the difference between active transport and group translocation.

Reference:
1. Metzler，David E.和Carol M. Metzler。“生物化学。”Google书籍。N.P.，N.D。网络。2017年5月17日。
2. “Active transport.” Wikipedia. Wikimedia Foundation, 14 May 2017. Web. 18 May 2017. .
3.“组易位 - PEP：PTS。”生命科学百科全书。N.P.，N.D。网络。2017年5月18日。。

Image Courtesy:
1. “Scheme sodium-potassium pump-en” By LadyofHats Mariana Ruiz Villarreal – Own work (Public Domain) viaCommons Wikimedia
2. Yikrazuul的“磷酸转移酶系统” - 自己的作品；ISBN 978-3-13-444608-1;S.505(CC BY-SA 3.0)viaCommons Wikimedia