简要说明Cori能量循环在代谢中的重要性

A Brief Explanation of the Importance of Cori Cycle in Metabolism

 

Cori循环是一个重要的代谢过程，它帮助我们的身体产生额外的能量，肌肉需要进行艰苦的活动。这篇生物学上的文章提供了关于Cori循环的简要说明。

 

你知道吗?

Cori循环以内科医生Carl和Gerty Cori(已婚夫妇)命名，他们在1929年首次将其绘制出来。

 

要了解人体的功能，就必须分析在其中发生的无数小过程。这些依赖和独立的过程协同工作，允许我们生活和执行我们的日常活动。

 

Cori循环是一个非常重要的过程，它帮助人体在进行剧烈活动时产生肌肉所需的能量。下面是对Cori循环的工作和意义的描述，首先讨论我们的肌肉所需要的能量是如何产生的。

　

　

 

肌肉活动的能量产生

我们身体的肌肉使我们能够完成所有的日常活动，包括行走、站立、跑步、举重等。它们产生的力量与正在进行的活动的强度成正比。对于这种力量的产生，需要能量。

 

对于肌肉活动，需要ATP(三磷酸腺苷)，这是一种称为糖原分解的过程。糖原(Glycogen)分解分解 葡萄糖(Glucose)，糖原储存在骨骼肌中释放葡萄糖。

 

在我们的日常活动中，我们的肌肉将葡萄糖和氧气结合在一起，在一个叫做糖酵解的过程中，产生两个ATP的单位和两个丙酮酸的单位。ATP直接作为细胞的能量，当有足够的氧气时，丙酮酸盐也会被进一步分解，以产生更多的能量。因此，这两种代谢化合物在细胞层面为肌肉提供能量，使它们发挥作用。

 

然而，当我们进行高强度的肌肉活动时，氧气的摄入量与肌肉的能量需求不成正比(氧气远远不够)了。在这样的情况下，由于氧气不足，葡萄糖通过一种称为发酵的无氧代谢过程分解，其中丙酮酸转化为乳酸，一种可溶性乳酸 （Lactate)小分子，然后分泌到血液中。

 

这使得化学过程能够在不使用氧气的情况下继续产生能量。在这种情况下，肌肉细胞可以在非常高的速率下进行有氧运动，但只能持续大约一到三分钟的时间，在血液中乳酸的积累变得过度，从而导致疲劳。

 

什么是Cori循环?

如果一项剧烈活动持续下去，身体会采取另一种代谢途径来摆脱乳酸，并继续进行有氧运动。这一能源生产过程被称为Cori循环。

 

在Cori循环中，积累在肌肉细胞的乳酸中被肝脏吸收。肝脏执行一种称为糖异生(gluconeogenesis)的化学过程，将乳酸转化为葡萄糖。

 

从本质上讲，糖异生过程逆转了身体所进行的糖酵解和发酵过程，从而产生乳酸。这首先将乳酸转化为丙酮酸，最后转化为葡萄糖。

 

这种葡萄糖随后被引入到血液中，并将其输送到工作肌肉中，在那里它被用来满足肌肉的额外能量需求。随后肌肉的乳酸产生又被肝脏吸收，因此Cori循环恢复。

 

当肌肉活动停止时，在Cori循环中产生的葡萄糖会通过糖异生来补充储存在肌肉中的糖原。

 

Cori循环的局限性

使用Cori循环，人体能够将代谢产物转化为肌肉的能量来源。然而，它不能无限地继续这样做。

 

与许多其他自然周期类似，Cori循环并不是完全封闭的循环。在肌肉中，糖酵解产生两个ATP的单位。然而，肝脏消耗6个ATP来进行糖原生成过程。Cori循环也需要氧气的初始引入，没有它，它就不能开始。因此，最终，肌肉必然需要新的葡萄糖和氧气供应。

 

如果体力活动过于剧烈，肌肉的能量需求就会超过Cori循环从乳酸中再生出葡萄糖的能力。这将导致一种称为乳酸酸中毒的疾病，它是系统中过量乳酸的累积。乳酸酸中毒会降低血液的pH值，从而导致组织损伤。它还会引起与恐慌有关的症状，如过度通气、腹部绞痛、呕吐。

　

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A Brief Explanation of the Importance of Cori Cycle in Metabolism

 

The Cori cycle is an important metabolic process that helps our bodies produce the additional amount of energy required by the muscles to perform grueling activity. This BiologyWise post provides a brief explanation about the Cori cycle.

 

Did You Know?

The Cori cycle is named after physicians Carl and Gerty Cori (married couple), who first mapped it in 1929.

To understand how the human body functions, it is essential to analyze the numerous smaller processes that take place within it. These dependent and independent processes work together in tandem, allowing us to live and perform all our daily activities.

 

The Cori cycle is one such important process that helps the human body produce the energy required by our muscles when performing a strenuous activity. The following is a description of the working and significance of the Cori cycle, starting with a discussion on how the energy required by our muscles is produced.

Energy Production for Muscle Activity

The muscles in our body enable us to perform all our daily activities, including walking, standing, running, lifting weights, etc. They produce an amount of force which is directly proportional to the intensity of the activity that is being performed. For the generation of this force, energy is needed.

 

For muscular activity, ATP (adenosine triphosphate) is required, which is produced in a process known as glycogenolysis. Glycogenolysis breaks down glycogen, which is stored in the skeletal muscles releasing glucose.

 

For most of our daily activities, our muscles combine glucose and oxygen aerobically, in a process known as glycolysis, which results in the production of two units of ATP and two units of pyruvate. ATP is directly used for energy generation, and when enough oxygen is available, pyruvate too is further broken down aerobically for generating more energy. Thus, these two metabolic compounds provide energy at the cellular level to the muscles, allowing them to function.

 

 

Running muscle anatomy man

However, when we perform a highly strenuous muscular activity, the amount of oxygen intake becomes disproportional (much less) to the energy requirement of the muscles. In such a scenario, since oxygen is insufficient, glucose is broken down through an anaerobic metabolism process known as fermentation, wherein, the pyruvate is converted to lactate - a soluble milk acid, and then secreted into the bloodstream.

 

This allows the chemical process responsible for energy generation to continue without the use of oxygen. In this manner, the muscle cells can produce energy anaerobically in this at very high rates, but only for about one to three minutes, after which lactate accumulation in the bloodstream becomes excessive, which leads to fatigue.

 

 

What is the Cori Cycle?

If a strenuous activity continues, the body adopts an alternate metabolic route to get rid of the lactate, and keep producing energy anaerobically. This process of energy production is known as the Cori cycle.

 

In the Cori cycle, lactate accumulated in the muscle cells is taken up by the liver. The liver performs a chemical process known as gluconeogenesis, to convert lactate back to glucose.

　

Pink Liver Icon

Essentially, gluconeogenesis reverses both the processes of glycolysis and fermentation that the body had performed to produce lactate. This first converts lactate to pyruvate, and then finally into glucose.

 

This glucose is then introduced into the bloodstream, which carries it to the working muscles, where it is used to feed the additional energy demands of the muscles. The subsequent lactate production by the muscles is again taken up by the liver, and thus the Cori cycle resumes.

 

In case the muscular activity ceases, the glucose generated in the Cori cycle undergoes glycogenesis to replenish the glycogen stored in the muscles.

Limitations of the Cori Cycle

Using the Cori cycle, the human body is able to convert metabolic by products into a source of energy for the muscles. However, it cannot continue to do so infinitely.

 

Similar to many other natural cycles, the Cori cycle isn't a completely closed loop. In the muscles, glycolysis results in the production of two units of ATP. However, the liver uses up six units of ATP to carry out the process of gluconeogenesis. The Cori cycle also requires the initial introduction of oxygen, without which it cannot begin. As such, eventually, the muscles are bound to require a new supply of glucose as well as oxygen.

 

If a physical activity is too strenuous, the energy requirements of the muscles will exceed the capacity of the Cori cycle to regenerate glucose from lactate. This will result in a condition known as lactic acidosis, which is an accumulation of excess lactic acid in the system. Lactic acidosis brings down the pH level of the blood, which can lead to tissue damage. It also induces symptoms associated with panic, such as hyperventilation, abdominal cramps, vomiting, etc., all of which are the body's natural defense mechanisms designed to slow down the rigorous activity, and prevent permanent damage from occurring.

 

A Brief Explanation of the Importance of Cori Cycle in Metabolism  https://biologywise.com/brief-explanation-of-cori-cycle