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 Related Pages: Protein Protein Detail |
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PROTEIN SYNTHESIS:
"Just hold on - I've got to get through this gate in the nuclear membrane."
"Hey! Look who came to meet us! The ribosomes! I'm always popular!
"They always jump all over me like that! It's just like coming home and having your puppy greet you at the door. Do you see how the ribosome are split into a small part and a large part. Each of those two parts is called a 'subunit' and is made up of many proteins and RNA. It's a special RNA made expressly for the purpose of using in ribosomes, called 'ribosomal-RNA'. I'm what they call 'messenger-RNA' because I carry the message of how to make a protein. "When the ribosome subunits jump onto my arm, they snuggle my arm between them and become a whole ribosome. This is the beginning of my ribosome buddys making protein. They can translate the secret code of my nucleotide sequence to create a protein with the correct amino acid sequence. "Let's watch them make a protein, then I'll show you the secret code and how it works.
"The ribosome crawls along messenger-RNA like me, and translates my secret code into which amino acid belongs where. Then it super glues the amino acids together. The chain of super glued amino acids is called a protein. "Now let's look really close and I'll show you the secret code. Promise not to tell anyone. Well, unless they really want to know. Ha! Ha! Ha!
"Ya see the secret code? The ribosome only looks at three nucleotides in a row. These three nucleotides are the code. They are like three letter words. In English, 'dog' and 'cat' and 'you' are three-letter words that mean different things. Those scientists call a three-nucleotide 'word' a 'codon'. Ya see, code is part of the word codon. Ain't them scientists a clever lot? "With 4 different nucleotide 'letters', you can make 64 different three-nucleotide 'words'. Each 'word' means: Put amino acid X here. There are only 20 different amino acids, so 64 'words' are more that enough to tell the ribosome what to do. Lets make our own message using three-letter English words.
"If we made this chain, someone would read the message and tell each person or animal where to get in line. As each one got in the right order, the reader would tell them to hold hands, or paws, to keep them in the right order. The ribosome does it slightly differently. The ribosome needs help with the reading part. It gets that help from my cousins, the transfer-RNAs. I have lots of cousins. Let's look at one cousin, cgc transfer-RNA.
"My cousins, the transfer-RNAs, help the ribosome read the three letter 'words' by having three nucleotides exposed on their bottoms. These three nucleotides are called an anti-codon because they fit exactly, like a puzzle piece, with my three-letter 'words' called codons. This cousin is the cgc-transfer-RNA, and she holds the correct amino acid on her top. Her amino acid is called 'alanine'. The cgc anti-codon on her bottom matches up with my codon gcg. In nucleotide language, gcg means: Put alanine here. Let's see how that would work with our English chain.
"So, that's really all there is to our secret code. The secret is that messenger-RNA, like me, is really a string of three-letter 'words' that tell the ribosome what the correct order of the amino acids are in a protein. " Come watch me and my ribosome and transfer-RNA buddies make a protein!" PROTEIN SYNTHESIS: For Parents & Teachers
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