BIOC 212 Lecture Notes - Lecture 41: Lysine, Ribose, Ribose 5-Phosphate
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Metabolism III
Nucleic Acid Polymerization
• Transcription of RNA or replication of DNA
o Other example of double hydrolysis is nucleic acid polymerization
• High energy intermediate is nucleotide triphosphate
• Hydrolysis to PPi then 2 Pi
o Adds nucleotide to polymer
o 2 ATP --> 2 ADP + PPi --> 2 ADP + 2 Pi
• Start with nucleotide
o Add an ATP, hydrolyse ATP twice
o Form intermediate which is nucleotide triphosphates --has same energetics
as ATP
• Very high energy intermediate
o Can condense this with nucleotide acid chain
o Cleave both alpha & beta phosphates, giving pyrophosphate that then gets
cleaved into two phosphates
• Large energy drop gives polymerization of nucleic acid
• Final product is 2 ADP + 2 Pi, but from different steps
o Different from amino acids, since two phosphates are coming from two
different steps
• Putting each P on in phase
o But net result is the same
o Using energy from 2 phosphates to drive condensation reaction
NADPH & NADH
• NADPH and closely related molecule NADH are other examples of carrier
molecule (other than ATP)
• Redox carriers
o Drive unfavorable redox reaction in the cell (redox reagents)
o Or control how redox reaction works
• NADP+ carries high energy electrons as reduced NADPH
o NADPH can exist in two forms; with hydrogen or without and has + charge
o NADPH is high energy form
• NADP+ is the low energy form
• Also NAD+ and NADH
o Works the same way
o High energy NADH form, and low energy NAD+