Respiration
IGCSE Biology Topic 12 5:00 English narration · English + 中文 subtitles burned in
Chapters
Transcript
Here is the single most common mix-up in IGCSE Biology.
这是IGCSE生物学中最常见的混淆。
Respiration is not breathing.
呼吸作用不是呼吸动作。
Breathing is moving air in and out of your lungs — a physical action, using muscles.
呼吸动作是把空气吸进和呼出肺部——这是一个用到肌肉的物理动作。
Respiration is a chemical reaction that happens inside every living cell, all the time — in your muscles, in a plant root, in yeast.
呼吸作用是一个化学反应， 它在每一个活细胞里一直进行着——在你的肌肉里、在植物的根里、在酵母里。
Get that distinction right and this whole topic opens up.
把这个区别弄对，整个专题就通了。
Welcome to respiration.
欢迎来到呼吸作用。
Aerobic and anaerobic, yeast and muscles, and the oxygen debt.
有氧和无氧、酵母和肌肉，还有氧债。
Let's begin.
让我们开始吧。
Watch it happen.
看它发生。
Glucose and oxygen go in, energy is released, and carbon dioxide and water come out.
葡萄糖和氧气进去，能量被释放，二氧化碳和水出来。
Respiration is the release of energy from food, and it happens in every living cell, all the time.
呼吸作用是从食物中释放能量，它在每一个活细胞里一直进行着。
Say it once more, because the wording is marked: the release of energy from food.
再说一遍，因为措辞是要评分的：从食物中释放能量。
Not the making of energy — energy is never made.
不是制造能量——能量从来不会被制造出来。
And it is not breathing.
而且它不是呼吸动作。
Cells use that energy for a long list of jobs, and the exam picks from it.
细胞把这些能量用于一长串工作，考试会从中挑选。
Muscle contraction, so you can move.
肌肉收缩，让你能动。
Protein synthesis, to build proteins.
蛋白质合成，用来建造蛋白质。
Cell division, to make new cells.
细胞分裂，产生新细胞。
Active transport.
主动运输。
Growth.
生长。
Carrying nerve impulses.
传递神经冲动。
And keeping your body temperature constant.
还有保持体温恒定。
Aerobic respiration uses oxygen to break down nutrient molecules, mainly glucose, and release energy.
有氧呼吸利用氧气分解营养物质，主要是葡萄糖，并释放能量。
The clue is in the name: aero means air.
英文名字里就藏着线索：aerobic 里的 aero 意思是"空气"。
Learn the word equation exactly — glucose plus oxygen gives carbon dioxide plus water.
要准确记住文字方程式—— 葡萄糖加氧气生成二氧化碳加水。
For the supplement paper, learn the balanced equation too: one glucose and six oxygen give six carbon dioxide and six water.
补充部分还要记住配平方程式： 一个葡萄糖和六个氧气生成六个二氧化碳和六个水。
And remember the key comparison point: aerobic respiration releases a lot of energy from each glucose molecule, because the glucose is broken down completely.
还要记住关键的比较点：有氧呼吸从每个葡萄糖分子释放出大量能量， 因为葡萄糖被完全分解了。
Anaerobic respiration breaks down glucose to release energy without using oxygen.
无氧呼吸在不使用氧气的情况下分解葡萄糖以释放能量。
It releases much less energy from each glucose molecule than aerobic respiration does — and you must be able to say why.
它从每个葡萄糖分子释放的能量比有氧呼吸少得多——你必须能说出为什么。
Because without oxygen the glucose is not fully broken down.
因为没有氧气，葡萄糖没有被完全分解。
The products still contain energy that was never released.
产物中仍然含有从未被释放的能量。
That is the reason, and simply writing "less energy" without it does not get the mark.
这就是原因， 只写"能量较少"而不说原因是得不到分的。
In yeast, the equation is: glucose gives alcohol plus carbon dioxide.
在酵母中，方程式是：葡萄糖生成酒精加二氧化碳。
Both products are useful to us, and that is worth knowing.
两种产物对我们都有用，这值得知道。
The carbon dioxide makes bread rise — those bubbles in a loaf are yeast respiring.
二氧化碳让面包发起来—— 面包里的那些气泡就是酵母在呼吸。
And the alcohol is what brewing depends on.
而酒精正是酿造所依赖的。
You can also investigate respiration with yeast: warmer yeast respires faster, up to its best temperature, and you can measure that by counting the bubbles of carbon dioxide it gives off.
你也可以用酵母研究呼吸作用：温度越高酵母呼吸越快，直到它的最适温度， 你可以通过数它放出的二氧化碳气泡来测量。
Past the best temperature the rate falls again, because the enzymes are denatured.
超过最适温度后速率又下降，因为酶变性了。
For the supplement paper, your muscles do it differently.
补充部分：你的肌肉做法不同。
During hard exercise they cannot get enough oxygen, so they respire anaerobically.
剧烈运动时它们得不到足够的氧气， 所以进行无氧呼吸。
But the equation is not the yeast one.
但方程式不是酵母那个。
In muscles, glucose gives lactic acid — no alcohol, no carbon dioxide.
在肌肉里，葡萄糖生成乳酸——没有酒精，没有二氧化碳。
That lactic acid builds up in the muscles and in the blood, and it creates an oxygen debt: the extra oxygen your body will need later to break that lactic acid down.
乳酸在肌肉和血液中积累，产生氧债： 也就是你的身体稍后需要的额外氧气，用来分解那些乳酸。
After you stop exercising, the debt is repaid, and three things happen together.
你停止运动后，氧债会被偿还，有三件事同时发生。
Your heart rate stays high, carrying the lactic acid in the blood from the muscles to the liver.
你的心率保持很高，把血液中的乳酸从肌肉运到肝脏。
You keep breathing deeply and quickly, taking in extra oxygen.
你继续深而快地呼吸，吸入额外的氧气。
And the liver uses that oxygen to break the lactic acid down by aerobic respiration.
肝脏用这些氧气通过有氧呼吸把乳酸分解掉。
Now the exam question.
现在是考题。
A runner sprints hard for twenty seconds, then breathes deeply for several minutes afterwards.
一个跑步者全力冲刺二十秒，停下来后深呼吸好几分钟。
Why?
为什么？
During the sprint the muscles could not get oxygen fast enough, so they respired anaerobically and lactic acid built up, creating an oxygen debt.
冲刺时肌肉无法足够快地获得氧气，所以进行无氧呼吸，乳酸积累，产生氧债。
The deep breathing afterwards takes in the extra oxygen the liver needs to break that acid down.
之后的深呼吸吸入肝脏分解那些乳酸所需的额外氧气。
The breathing repays a debt built up during the sprint — it is not simply because the muscles are still working.
这个呼吸偿还的是冲刺期间积累的债——而不是简单地因为肌肉还在工作。
Three marks to lock in.
锁住三个分。
First: respiration is not breathing — it releases energy in every living cell, all the time.
第一：呼吸作用不是呼吸动作——它在每一个活细胞里一直释放能量。
Second: there are two anaerobic equations, and they are different.
第二：有两个无氧方程式，而且它们不一样。
Yeast gives alcohol plus carbon dioxide; muscles give lactic acid.
酵母生成酒精加二氧化碳； 肌肉生成乳酸。
Third: the oxygen debt is repaid by a fast heart rate and deep breathing, with the liver breaking the lactic acid down.
第三：氧债通过高心率和深呼吸偿还，由肝脏分解乳酸。
Master these, and this topic is yours.
掌握这些，这个专题就是你的了。