英语听力细胞是啥它们如何作业

You are cells: your muscles, organs, skin and hair. They are in your blood and in your bones. Cells are biological robots. They don’t want anything; they don’t feel anything. They are never sad or happy. They just are, right here, right now. They are as conscious as a stone, or a chair, or a neutron star. Cells just follow their programming that has been evolving and changing for billions of years, molded

by natural selection. They are impossible machines, and yet, here they are, driven entirely by the fundamental forces of the universe – the smallest unit of life, right at the border where physics becomes biology.

Sometimes, to get a truer understanding of how amazing something is, you need to hold your breath and dive in really deep. So, what are cells and how do they work?

Look around the room you are sitting in right now. Let’s fill it top to bottom with trillions of grains of sand, billions of grains of rice, hundreds of thousands of grapes, a few thousand apples and a dozen watermelons. This is what the inside of your cells looks like. In terms of numbers, they’re mostly filled up with water molecules – the grains of sand. Water gives a cell’s insides the consistency of soft jelly and enables

other things to move around easily. Almost all the other things, the rice and fruit, are proteins – several billion in total, more than 10,000 different kinds, depending on the function of the cell.??

Your cells are basically protein robots, as is all life really. In fact, all solid, nonfat parts of your body are mostly made out of protein – even your bones. Proteins are dead things that make life happen. How does this work?

The Language of Life

Cells need to do many very hard things to stay alive: get food in and waste out, grow and build structures, escape danger or react to stimuli, make copies of themselves and so on. All of this is done by speaking the language of life. And the words of this language are proteins. This is how this language works in a nutshell.

It all

begins with amino acids, tiny organic molecules. They’re the alphabet of the language of life. There are 21 different ones, like different letters: amino acid A, amino acid B, C and so on. If you put around 50 amino acids together, they form a protein, which in the language of life is a word. And if you put many of these protein words together, you get a sentence, called a biological pathway.

Let’s oversimplify a bit and say, for example, your cell needs to break down sugar with the language of life. It may take the amino acids for the letters B, R, E, A and K, to form the protein word “break”. Then, combine this word with other protein words to form a biological pathway “sentence” that means “break down sugar”.

In reality, this language of life is so complex that it defies imagination. You need to know about 8,000 words to speak a human language really well. But in the language of life, there are an estimated 20,000. And while the average English word has five letters, human proteins have an average of 375 amino acids. The longest protein has more than 30,000. And cells need to execute thousands of steps at any moment. If they ever stop speaking the language of life, they die.

OK. But how do mindless cells speak a language this complex? Let’s dive a little deeper.

There are 21 amino acids that can be combined to form proteins. And proteins are made up of dozens, to hundreds, to thousands of amino acids. For the average protein length of a human cell of 375 amino acids, you get a stunning 6.8x10^495, possible proteins your cells can make – a quadrillion googol googol googol googol times more than there are atoms in the universe.

Most of these possible proteins are useless, just like with human language, most random letter combinations are just gibberish. So you need to know which words, which proteins, make up a language to speak it properly. And this is the job of your DNA, a long sequence of instructions.?

If you untangled a cell’s DNA, it would be about two meters long. All of your body’s DNA combined into one long string would reach to the sun and back over 20 times. Around 1% of your DNA is made up of genes – which are basically protein dictionaries that contain all the words of the language of life your cells speak. But genes are also the building manuals for all the proteins your cells need to function.

The rest of your DNA is probably not useless, but basically like a set of rules. It’s like the book of grammar of the language of life: which proteins need to be built, at which time? How many of them do you need? Which protein words go together and why?

Ok. Letters, words, sentences, dictionary and grammar. But of course, this is all just a metaphor for something mind-numbingly complex. Let’s dive a little deeper to catch a glimpse of reality.

How Dead Proteins Make Life

Now that we have some basic principles, we have a chance to understand how dead things make life together. And for that, we need a fundamental force of the universe: electromagnetism.??

The elementary particles that make up atoms, which make up amino acids, have different charges that attract or repel each other. The 21 different amino acids all have slightly different charges. Some are more negative, others more positive. When your cells build proteins, they put different amino acids together in chains, basically long strings. Now, because of the different charges of the amino acids used, these strings begin to fold in on themselves. This folding process is so complex that we still haven’t completely understood how exactly it works. But in a nutshell, 1D strings become 3D structures.

Proteins are basically 3D puzzle pieces with a very specific shape. In the world of proteins, shape is everything. Because its 3D shape determines which areas of a protein are charged in which way, and this determines how it can interact with other proteins.?

All of these differently charged puzzle pieces can snap together or repel each other. When they snap together, their charge changes, which can make them change their shape, which then makes them a new protein, a new tool that can do new things. This is what makes proteins so incredibly powerful. You can do basically everything with them. They can snap together like Lego pieces to build complex structures. They can dismantle things. They can form complex micro machines that use energy to do work. And maybe most stunningly, they can convey information.

Let’s say there is a toxic chemical entering your cell. There may be a protein shaped to snap to that toxin. If the protein finds that toxin, it changes its shape. With that new shape, it can now snap into a different protein that changes its shape again. This new protein activates a micro machine that directly binds to your DNA to order the production of a special protein, which acts as an antidote to the toxin. This cascade of interaction is the pathway we spoke about earlier, a sentence in the language of life.

So, without a single active thought, proteins have fixed a problem and saved the cell’s life. In reality, these pathways can have dozens to hundreds of steps. How life operates is so incredibly awe-inducing! Somehow, mind-numbingly complex interactions between dumb and dead proteins create a less dumb and less dead cell. Somewhere around here life happens, but we still don’t know what life is.

How Dumb Things are Smart Together

We need another analogy, so let’s talk about ants. Ants share a fundamental property with cells: they are really dumb. A single ant will just stumble around uselessly. But if you put a lot of ants together, they exchange information and do amazing things: constructing complex structures, organizing themselves, caring for broods, or attacking enemies. Although dumb individually, together, they become something greater. This phenomenon occurs all over nature, and is called emergence. It is the observation that entities have properties and abilities that their parts do not have. This is how everything in your body works. Your cells are bags of proteins guided by chemistry. But together, these proteins form a living being that can do a lot of really sophisticated things. Cells are mindless robots that are even dumber than ants. But many of them acting together form specialized tissue and organ systems –

from muscles that make your heart beat to brain cells that make you think.?

If you look outside at the incredible dimension and scale of space, a place where forever is a real thing, it’s almost impossible not to feel a bit small. Not special. But if you look inside, into what you really are, you just discover almost indescribable complexity – the beautiful language of life.