Metabolism

Metabolism is a generic term for all the chemical reactions that break down or "burn" food to provide energy for the operation of an organism. The word "burn" is used advisedly, because the energy yield from a food in the human metabolic process is comparable to the energy obtained by actual combustion. The energy available from a food is commonly stated in dietary Calories, and the Calorie rating of a food may actually be obtained by burning it in a pure oxygen atmosphere in a calorimeter to measure the energy yield from this combustion.

代谢是指所有分解或‘燃烧’食物以提供生物体运作所需能量的化学反应的总称。使用‘燃烧’这个词是谨慎的，因为食物在人体代谢过程中释放的能量与实际燃烧时获得的能量相当。食物中可提供的能量通常以饮食热量（Calories）表示，食物的热量值实际上可以通过在纯氧氛围中在量热计中燃烧该食物来测量其燃烧产生的能量。

Like ordinary combustion, the metabolism of food requires a supply of oxygen and produces carbon dioxide as a combustion product. For various foods one can state a representative energy yield, an amount of oxygen required, and an expected amount of carbon dioxide released. Here are some values from Nelson.

如同普通燃烧一样，食物的代谢也需要氧气供应，并产生二氧化碳作为燃烧产物。对于各种食物，可以给出代表性的能量产出、所需的氧气量以及预期释放的二氧化碳量。以下是一些来自Nelson的数据。

Note that the amount of energy produced for the four types of food is roughly proportional to the amount of oxygen use, so that the metabolic rate can be measured by measuring the rate of oxygen consumption. However, the amount of carbon dioxide produced by the four types of food is different, so the ratio CO₂/O₂ provides some information about the type of food being utilized.

注意，四种食物产生的能量大致与氧气消耗量成正比，因此可以通过测量氧气消耗速率来测定代谢率。然而，四种食物产生的二氧化碳量不同，因此CO₂/O₂的比值能提供关于所利用食物类型的某些信息。

The average for the three types of food in the above table is 4.7 kcal of energy release for each liter of oxygen consumed. On the average, an adult at rest consumes about 16 liters of oxygen per hour. This gives a nominal basal metabolic rate of 75 kcal/hr which translates to 87 watts.

上述表格中三种食物的平均能量释放为每消耗一升氧气4.7 kcal。平均而言，静息状态下成年人每小时消耗约16升氧气。这给出一个名义上的基础代谢率为75 kcal/hr，即87瓦。

Crucial to the metabolic process is the molecule adenosine triphosphate (ATP), considered by biologists to be the energy currency of life. Almost every process in the body that uses energy gets it from ATP, and in the process converts it to ADP. The energy from the oxidation of food (metabolism) is used to convert the ADP back to ATP, making the energy available for body processes. One of the main pathways for doing so is in the oxidation of glucose.

代谢过程的关键在于分子腺苷三磷酸（ATP），生物学家认为它是生命的能量货币。身体中几乎每一个需要能量的过程都从ATP获取能量，并在过程中将其转化为ADP。食物氧化（代谢）释放的能量用于将ADP重新转化为ATP，使能量可供身体过程使用。其中一条主要途径是在葡萄糖氧化过程中实现的。

Oxygen Required for Metabolism