Name: Scott
Status: Student
Grade: 9-12
Location: TX
Country: United States
Date: May 2006
Question:
Hi,
I am in 12th grade and studying biology. How is it that cells use
ATP to harness energy and transfer energy? I understand by reading
biology books that cells transfer a phosphate group off of the ATP
molecule to another molecule to activate that other molecule.
However, does it really work by transferring phosphate groups? For
instance, say if two unactivated amino acids needed to be joined
into a peptide bond. Wouldn't the enzyme just get two unactivated
amino acids into an active site and a molecule of ATP at some other
active site on the enzyme. Then the enzyme would hydrolyze ATP and
thereby release heat. The enzyme would harness the heat released by
the ATP hydrolysis and cram the two amino acids together to create a
peptide bond.
Isn't this the way it works by the enzyme just going ahead and
harnessing the heat released from the hydrolysis of ATP and not by
transferring phosphate groups? Thereby creating the peptide
bond.
Replies:
The way in which amino acids are activated to form a peptide bond is as
follows. An enzyme named amionoacyl-tRNA synthetase transfers a phosphate
group from ATP to the amino acid to form a short-lived complex called amino
acid-AMP. This same enzyme then catalyzes the reaction of the acivated amino
acid with it's specific tRNA molecule to form amino acid-tRNA + AMP. The
amino group of the amino acid-tRNA conjugate then reacts with the -COOH
group of the terminal amino acid of the nascent polypeptide being
synthesized by enzymes that are a part of the ribosome.
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