BIOL 300 Lecture Notes - Lecture 14: Atp Hydrolysis, Endergonic Reaction, Glutamic Acid
Michael Le
Arc
Biol 300
Foundations of Biology
The Energy Currency of the Cell: ATP:
● Reactions involve ATP
ATP Hydrolysis Releases Free Energy:
● ATP contains free energy
● This energy, the potential energy, is mostly in its phosphate groups since the phosphates
have negative charges that repel each other
● The breakdown of ATP is spontaneous and is also the hydrolysis of ATP
● Once the phosphate is released the negative repulsion is relieved and this spontaneous
reaction releases large amount of free energy
● ATP + H2O ADP + Pi , Pi is an inorganic phosphate (ΔG= -7.9 kcal/mol)
● ADP can be further broken down to AMP (monophosphate) but it won’t release as much
free energy
ATP and Energy Coupling:
● In order for ATP hydrolysis to be linked to an endergonic reaction without the energy
being wasted in such forms as heat:
○ Energy Coupling: when ATP hydrolysis is brought in close contact with the
reactant molecule of the endergonic reaction
○ The Enzyme Associated with this has a binding spot for the ATP and the reactant
and when the hydrolysis occurs the inorganic phosphate is bonded to the reactant
○ This reactant is now phosphorylated and is now less stable as well
○ An example of this coupling is with glutamine
○ To get glutamine we need: Glutamic Acid + NH3 Glutamine + H2O but this
reaction is not spontaneous and has a +ve ΔG therefore it occurs in 2 steps
■ 1. ATP + Glutamic Acid Glutamyl Phosphate + ADP ΔG= -ve
■ 2. Glutamyl Phosphate + NH3 Glutamine + Pi ΔG= -ve
○ These two reactions are coupled and are written as:
■ ATP + Glutamic Acid + NH3 Glutamine + Pi + ADP ΔG=-3.9
kcal/mol
○ We can also see that the difference between -7.9 and -3.9 (the ΔG of the
reactions) is now in the glutamine
○ The endergonic reactions in biological are made possible by coupling reactions
like this
Document Summary
This energy, the potential energy, is mostly in its phosphate groups since the phosphates have negative charges that repel each other. The breakdown of atp is spontaneous and is also the hydrolysis of atp. Once the phosphate is released the negative repulsion is relieved and this spontaneous reaction releases large amount of free energy. Atp + h2o adp + pi , pi is an inorganic phosphate ( g= -7. 9 kcal/mol) Adp can be further broken down to amp (monophosphate) but it won"t release as much free energy. In order for atp hydrolysis to be linked to an endergonic reaction without the energy being wasted in such forms as heat: Energy coupling: when atp hydrolysis is brought in close contact with the reactant molecule of the endergonic reaction. The enzyme associated with this has a binding spot for the atp and the reactant and when the hydrolysis occurs the inorganic phosphate is bonded to the reactant.
