Name: cell energy loss and entropy
Uploaded: 2023-04-30T10:41:06.000Z
Duration: 1 min 22 s
Channel: JoVE
Description: Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Energy

HS-PS3-1

Entropy within the Cell

活细胞遵循热力学第二定律，该定律指出，在没有外界输入的情况下，系统倾向于从低熵的有序状态向高熵的无序状态发展。
例如，氧气从肺部向含氧量较低的血液进行被动运输时，高浓度的氧气会扩散，从而使氧分子分散，增加系统的熵。
细胞通过分解葡萄糖等分子获取能量。反应的副产物——二氧化碳、水和热量被释放到周围环境中，从而增加了环境的熵。
细胞的存活依赖于高度有序的系统，例如DNA和蛋白质。这些有序结构的形成会导致系统熵的降低，因此必须伴随着周围环境熵的相等或更大的增加。
单条DNA链处于无序状态，当它们重新退火形成有序的双螺旋结构时，其熵会降低。
同时，在双螺旋结构形成过程中，能量会释放到周围环境中。这种能量使周围环境变得更加无序，从而增加其熵值。

细胞内的熵

活细胞的主要任务是获取、转化和利用能量来做功，这似乎很简单。然而，热力学第二定律解释了为什么这些任务比看起来更困难。宇宙中的能量传递都不是完全有效的。在每次能量转移中，都会有一部分的能量以无法使用的形式损失掉。大多数情况下，这种形式是热能。从热力学角度来说，热能被定义为从一个系统转移到另一个系统的非功能量。例如，在细胞代谢反应期间，一些能量以热能的形式损失。

物理系统中的一个重要概念是有序和无序。系统向周围环境损失的能量越多，系统的有序性就越低，随机性就越强。科学家将系统内随机性或无序性的度量称为熵。高熵意味着高无序性和低能量。分子和化学反应也有不同的熵。例如，当一个地方高浓度的分子扩散并扩散开时，熵会增加。

生物是高度有序的，需要不断的能量输入才能维持低熵状态。当生命系统吸收能量储存分子并通过化学反应转化它们时，它们会在此过程中损失一些可用能量，因为没有任何反应是完全有效的。 它们还产生不是有用能源的废物和副产品。这个过程增加了系统周围环境的熵。由于所有能量转移都会导致一些可用能量的损失，因此热力学第二定律指出，每次能量转移或转化都会增加宇宙的熵。尽管生物是高度有序的并保持低熵状态，但由于每次能量转移发生时可用能量的损失，宇宙的总熵不断增加。从本质上讲，生物体在与宇宙熵不断增加的这场连续斗争中，始终在努力保持自身的有序状态。

一个活细胞获取、转化和利用能量以完成生命活动的基本任务看似简单。然而，热力学第二定律……

Education

教育

JoVE Core

Cell Biology

细胞生物学

Unit 1

第一单元

Energy and Catalysis

能量与催化

KEY TERMS AND CONCEPTS

关键术语与概念

cell energy loss and entropy

Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

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Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

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New York State Science Learning Standards

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HS-PS3-6

Cell Energy Loss and Entropy

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