Question

Can someone help me understand this picture about translation in protein synthesis?

Answer 1

can you repost the picture? it didn't attach

Answer 2

me to

Answer 3

http://prntscr.com/a48fie

@aaronq
@swaggkingpatrick

These are the details of the picture according to my book. Translation -In the translation phase of protein synthesis the nucleic acids (base sequence) is translated into the language of proteins -translation occurs in the cytoplasm and involves three major varieties of RNA Translation consists of the following events -Once the mRNA attaches to the ribosome (step 2) tRNA comes and ferries the amino acids to the ribosome where they are bound together by enzymes in the exact sequence specified by the gene and its mRNA -tRNA also have to recognize the mRNA codons they are taking -they can recognize them because they have a special three-base sequence called an anticodon on their head that they can bind to (step 3) -Once the first tRNA has made its way into the correct position at the beginning of the mRNA message, the ribosome moves the mRNA strand along, bringing the next codon into position to be read by another tRNA. As amino acids are brought to their proper positions along the length of the mRNA they are joined together by enzymes (step 4) -As amino acid bonds to the chain its tRNA is released and moves away from the ribosome to pick up another amino acid (step 5) I need help understanding steps 3 and 4. Would like to do a live lesson.

Answer 4

what exactly don't you understand about it? do you need a visual, or more details?

Answer 5

@aaronq

So, in step 1, it says the mRNA is specifying one polypeptide that's made on a DNA template. What do they mean when they say this? A DNA template is a set of instructions made of nucleotides. I know what a template is, but I don't know what they're trying to say.

For step three, it says that after the mRNA attaches tRNA comes into pictures and ferries the amino acids to the ribosome where they are bound by an enzyme (so they're talking about the synthetase enzyme bonding them right)? If so, I don't understand what they mean when they say they are bound together by enzymes in the exact sequence specified by the gene and its mRNA. What do they mean by exact sequence specified by the gene and its mRNA? This is what is throwing me off. It then says tRNA also has to recognize the mRNA codons they are taking. I understand the tRNA recognizes the codons with its anticodon head, but I don't understand what they're saying when they say it recognizes a matching (complementary) mRNA codon calling for its amino acids. What do they mean by calling for its amino acids and why are the codons calling for the amino acids? In step four, it says the ribosome moves the mRNA strand along bringing the next codon into position to be read by another tRNA. What do they mean by read? In the picture, it shows a tRNA head with letters CGG next to the codon GCC. What's happening there? Letters are being added to the codon by the anticodon or what? Also, where did the long chain of polypeptides come from? Why all the sudden are there a ton of amino acids together? How did that happen?

@aaronq

Answer 6

do u get it

Answer 7

Tim is 7. His brother is 12.

Which fraction represents Tim's age compared to his brother's age?

A.


B.


C.


D.

Answer 8

@swaggkingpatrick

No offense, but you're posting in the wrong section and this is my question haha.

Answer 9

sorry

Answer 10

they're just saying that an mRNA strand codes for a single protein, and that the mRNA strand itself is a copy of a segment of DNA gene (although somewhat chemically different i.e. RNA).

"What do they mean by exact sequence specified by the gene and its mRNA?"

a gene is a segment of DNA that codes for a protein - there are more complications to this, but that's the basic idea.

The sequence of the nucleotides in the mRNA molecules indicates the order and identify of the amino acid that follows. Every 3 nucleotides (a codon), a new amino acid is added.

"What do they mean by calling for its amino acids and why are the codons calling for the amino acids? "

This is sort of semantics, all it means is that a codon indicates that a specific amino acid will follow - it doesn't "call" anything, it indicates through chemical recognition.

By "read" they mean what i just mentioned, recognized by complementarity. Like a puzzle piece needs to find it's adjacent partner. There is no physical reading, these are just easy words to explain what is happening.

The codon is recognized by the anticodon, these are "chemical puzzle pieces", they are able to recognize one another and favourably interact (i.e. bind).

Also, where did the long chain of polypeptides come from? Why all the sudden are there a ton of amino acids together? How did that happen?

That's exactly what translation is.

The mRNA molecule specifies a protein by it's sequence of nucleotides, these are recognized by anticodons in groups of 3. The anticodon will be "complementary" to the codon - Adenine is complementary to Uracil, and Guanine to Cytosine.

For example, if you have mRNA strand:

AAA CCC GGG, the complementary anticodons will be UUU GGG CCC

so each tRNA has an amino acid bound; when the ribosome attaches to the mRNA strand, tRNA molecules (that are always floating around the ribosome) will try to attach, when there is successful match, the tRNA molecule (carrying an amino acid) will bind to the mRNA-ribosome complex.

There are 3 sites on the ribosome, the middle one has the ability to "stitch" adjacent amino acids, the resulting strand of amino acids is the primary structure of a protein - this strand then folds a bunch of times will the help of other molecules and when it's folded into the right shape, it is a functional protein.

Let me know if that helps.

Answer 11

@aaronq


a gene is a segment of DNA that codes for a protein - there are more complications to this, but that's the basic idea.

The sequence of the nucleotides in the mRNA molecules indicates the order and identify of the amino acid that follows. Every 3 nucleotides (a codon), a new amino acid is added.

The amino acid that it connect to by the enzyme? So, the tRNA (RNA) decides what letters go on the amino acid when it's joined by the enzyme?

Answer 12

there aren't any letters on the amino acid. The tRNA molecule has a recognition part for the amino acid based on what anticodon it has (there is some repetition).

The codon-anticodon pairing is what determines which amino is brought next.

Answer 13

The codon-anticodon pairing is what determines which tRNA is brought next, is what i meant, but since tRNAs are attached to amino acids, it's both.

Answer 14

@aaronq
Hm, so, in step 2 (which I'm referring to), the amino acid isn't joined to tRNA by an enzyme? Also, the lle letters on the amino acid in step 3 in the picture I sent you, they're not really there?

Sorry this isn't clicking yet haha. I'll get it eventually though.

Answer 15

Oh that's what you're referring to, yes the amino acid is attached to the tRNA by an enzyme (all work done in living organisms are done by enzymes, by the way).

Yes, the "UAU" right? that's the anticodon that recognizes the codon (on the mRNA), they're not really letters, but nucleotides (the whole tRNA molecule is actually made of nucleotides).

Answer 16

@aaronq
Okay now it's clicking a bit
So, the letters on the lle amino acids were formed when it was connected to the tRNA? If so, what caused those "letters" to form.

Answer 17

wait, what do you mean by "IIe"?

Answer 18

ohh wait i see it.

Answer 19

@aaronq
Oh, in the picture, there is an amino acid with lle on it in step 3.

Answer 20

those are short forms of the names of the amino acid, ILE means isoleucine.

Answer 21

@aaronq

OH. What about the letters UAU. What are they from?

Answer 22

U means uracil and A adenine, those are nucleotides

Answer 23

dont know

Answer 24

those are part of the RNA strands, either mRNA or tRNA

Answer 25

@aaronq

The sequence of the nucleotides in the mRNA molecules indicates the order and identify of the amino acid that follows. Every 3 nucleotides (a codon), a new amino acid is added.

Okay, for this, is this referring to when the amino acid and tRNA are connected by the enzyme? I just wanted to make sure before I continue.

Answer 26

No this is referring to step 3, when the charged tRNA (meaning already bound to it's corresponding amino acid by the synthase enzyme) approaches the mRNA-ribosome complex.

Answer 27

@aaronq
Okay, so I'm still confused by that step. If it decides the amino acid that follows, why is there already an amino acid attached to it? What do you mean the amino acid that follows? You also said for every 3 nucleotides (a codon) an amino acid is added? What does this mean?

Answer 28

the mRNA decides what the sequence of amino acids will be. By "follows", i mean is next in the sequence.

Each 3 letter (nucleotide) bundle (codon) will recognize an anticodon on a tRNA (already carrying the amino acid).



So if you had an mRNA with 9 nucleotides, the protein will be 3 amino acids long. If you have an mRNA with 300 nucleotides, the protein will be 100 amino acids long.