Second Half F24 II: Lecture Slides 18 - 31 Flashcards
What is Adenosine Triphosphate?
The energy currency of the cell
Who discovered ATP?
Fritz Lipmann
What is ATP?
It is a nucleotide that consist of a base (adenosine), a sugar (ribose) and three phosphate groups labelled beta, alpha, gamma
How much ATP would a 70kg person use?
Approximately 40kg during a restful day.
How do cells use a catabolism (exergonic) breakdown in terms of ATP?
Cells breakdown nutrient molecules and use the available free energy to synthesize ATP from ADP
How do cells use Anabolic (endergonic) in terms of ATP?
The ATP synthesized in a catabolic pathway, donates its free energy to the anabolic pathway for synthesis of macromolecules and metabolic intermediates, and active transport across membranes.
What is the typical lifetime of an ATP molecule?
Seconds to minutes
What happens in the hydrolysis of ATP?
ATP reacts with H2O to break bonds and form ADP
What are most hydrolysis reactions?
They are favourable
What does a Favourable Reaction Mean in terms of Delta G?
A reaction is thermodynamically favourable if the products have a lower Gibbs free energy than the starting materials.
What does the value of Delta G depend on?
It depends on the nature of the bond being hydrolyzed
What are the typical delta G values for amides, esters and phosphoesters?
15 - 20kJ/mol
What is the Delta G for the Hydrolysis of ATP?
-50kJ/mol
What does the Delta G0 ‘ value state?
The Gibbs free energy Value under Standard Conditions
- pH = 7
- Temperature = 25 C
What is the Delta G0’ Value for ATP Hydrolysis?
-30.5kJ/mol
Where does all of the energy releasing and energy requiring processing take place?
At the phosphates
What does hydrolysis release?
The electrostatic repulsion among the negative charges
ATP –> ADP + Pi (neg. charge)
What does the product inorganic phosphate have?
Due to its negative charge and low energy, it forms a better resonance stabilization than ATO
What does a Negative Gibbs free energy?
That the reaction is favourable
What is the equation for Delta G0’?
Free Energy of Products - Free Energy of Reactants
How many Phosphoanhydride “high energy bonds” are there in ATP?
Two linkages in ATP
What is the nucleophile in terms of the hydrolysis of ATP?
The Water
What are the two nucleophile attacks within the hydrolysis of ATP?
1.) The gamma phosphate (electrophile) and the hydrolysis will be between the link between gamma and beta phosphate
2.) Hydrolysis of the a-B linkage (nucleophile attack on the a phosphate)
How much energy does the hydrolysis of the gamma phosphate of ATP yield?
About -30kJ of energy (Delta G’0 = -30.5kJ)
Which phosphate from ATP turns into the inorganic phosphate?
The gamma phosphate (leaving group)
What is the reaction when the nucleophile attacks the a phosphate?
ATP to AMP + PPi
(yields AMP and pyrophosphate (PPi)
What happens to PPi?
It is immediately hydrolyzed by the enzyme pyrophosphatase to give two moles of Pi (2Pi)
What does the hydrolysis of PPi result in?
The hydrolysis of both the phosphoanhydride bonds.
What is the free energy of the hydrolysis of ATP to AMP + 2Pi compared to the hydrolysis of ATP to ADP + 2Pi?
The hydrolysis to AMP takes twice as long releasing more energy due tp the breakage of more phospo anhdyride bonds (high energy)
What is the Gibbs free energy of the Hydrolysis to AMP?
-64.8 kJ
What type of reaction is the hydrolysis of ATP?
Exergonic due to the energy being released when the phosphoanhydride bonds break?
What happens in the synthesis of Glutamine?
NH3 acts as a nucleophile and attacks the electrophilic C on the glutamate molecule, it uses the hydrolysis of ATP to form into Glutamine
What is the first step of Glutamine Synthetase?
ATP reacts with Glutamate to produce a covalent intermediate, a mixed anhydride of phosphate and glutamate (enzyme bound intermediate)
What is the second step of Glutamine Synthetase?
NH3 acting as a nucleophile, reacts with the electrophile carbonyl carbon atom. Pi, the leaving group is displaced.
Why is ATP chemically versatile?
The phosphate group can participate in a variety of chemical reactions with common organic functional groups
In addition to the phosphoric group, what can ATp also transfer?
PPi or AMP to a substrate or to an amino acid residue to drive certain reactions forward.
What does ATP provide energy through?
Not simple hydrolysis but group transfer (simple hydrolysis loses energy)
What is the Gibbs free energy of Pi
0
What is the Gibbs free energy of the Hydrolysis of Glucose-6-phosphate?
-15 (low energy)
What are some high energy compounds?
Acetyl-CoA, Creatine Phosphate, 1,3 - biphosphoglycerate, Phosphoenolpyruvate
Why would ATP And GTP have similar Delta G Hydrolysis Values?
GTP is comparatively equivalent to ATP as it is also utilized as an energy source and phosphate donor in metabolic processes, however ATOP may have been chosen due to evolution purposes
Both Purines
