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Valentine10 Valentine10
wrote...
13 years ago
'What is the molarity of a 50 microgram per mL solution of transfer RNA? [NB tRNA molecules are roughly 80 nucleotides long and the average relative molecular mass of a nucleotide subunit is 320] Give answer to 3 significant figures and in scientific notation.'

My first thought was to multiply 80 by 320(=25600) and that would be the mass of one tRNA molecule and then possibly convert that to micrograms.... then no idea

I'm not really sure how to do this question at all. Help would  be greatly appreciated Slight Smile


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wrote...
Staff Member
13 years ago
80 * 320 would give you the molecular mass of tRNA molecule (You're right = 25600). Molarity is typically in the unit mol/L of simply (M). So they presumably want your answer in mol/L

molar mass (g/mol) = molecular mass * ((1/6.022)*10-23g/u)*(6.022*1023/mol)

50 ug / mL Rightwards Arrow convert to g/L Rightwards Arrow than divide this number by the molar mass you get from the above equation.

I think that's how you do it, but I'm not totally sure.
- Master of Science in Biology
- Bachelor of Science
Valentine10 Author
wrote...
13 years ago
I'm not really following your answer sorry.

When I did your calculation I got an answer of 1.95e-6. I don't really think that would be correct for the molarity, but then again I don't really know.

Why did I have to convert the ug/mL to g/L?

Neutral Face

Valentine10 Author
wrote...
13 years ago
Im definately not getting this right at all by using this method. Can anyone please help me!?
wrote...
Valued Member
Educator
13 years ago
Yeh, I'm not too sure, I did what duddy said also and I got the same answer. It does make sense though, see the attachment.
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Valentine10 Author
wrote...
13 years ago
Ok thanks.
wrote...
Valued Member
Educator
13 years ago
Did you end up getting the right answer? I'd love to know if what we got was correct for future reference Sad Dummy
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