Confusion between a nucleotide and nucleoside - (Jan/09/2011 )

Hi,

According to my lecturer, a nucleoside is a base + a sugar, where as a nucleotide is this with a phosphate group attached.

I read in my text book that during DNA replication there are many free nucleotides present around the replication fork called deoxyribonucleoside triphosphates, in which the two phosphate groups are removed during replication to release energy and so forms a regular nucleotide. What I do not understand is the term "deoxyribonucleoside triphosphate," has my text book made a typo? Surely it should be called deoxyribonucleotide triphosphate?

I would be grateful for a reply,

Thanks.

Kira on Mon Jan 10 00:05:13 2011 said:

Not a typo. You laid it out in your first sentence. A nucleoside is simply the sugar + base, so ATP is a nucleoside (sugar + adenosine base) tri-phosphate (3 phosphates). If you were to say nucleotide triphosphate, you'd be redudantly saying it had phosphates, since the term nucleotide implies a phosphate...then you go and say it contains phosphate a second time.


This is similar to how people say "ATM Machine", it seems to sound fine, but it is certainly not the correct thing to say. ATM stands for Automated Teller Machine...so when you say "ATM Maching", you're saying "Automated Teller Machine Machine". This is pretty equlivant to saying nucleotide triphosphate instead of nucleoside triphosphate.

Kaioshin on Wed Jan 12 01:10:07 2011 said:

I like the analogy