ATP - Cellular Energetics - RS Flashcards
How do cells comply with the second law of thermodynamics (entropy is always increasing)?
ATP drives work function returning energy to the environment as heat (IR photons). Life disorders its surroundings more than it orders itself by disordering light energy. From visible photons to IR photons it goes from 1 photon to about 80 thus much more disordered and ultimately in compliance with 2LOT.
Why is ATP energy rich?
The charge repulsion is relieved upon breaking the alpha beta or beta gamma bonds.
Greater resonance stabilization of products, ADP + Pi or AMP + PPi.
More favorable interactions of products with water.
What are the 3 main work functions that ATP directly or indirectly drives?
Mechanical work, Transport work, Biosynthetic work.
Energy storage is a 3-tier system, list the immediate, intermediate, and long term storage of energy:
Immediate - ATP
Intermediate - Glycogen
Longterm - Fats and proteins.
Why is ATP well suited for its role as an energy carrier?
The number of P is variable.
It is soluble and mobile.
High affinity binding to enzymes
Recognition handle.
Why are ATP’s phosphoric acid anhydride bonds well suited for a role in energy transfer?
It has an intermediate thermodynamic value consistent with ATP’s role as an acceptor, as well as a donor, of energy.
What is the common intermediate principle?
The exergonic reaction X -> Y is obligatorily coupled to the endergonic reaction by a common intermediate in both reactions. The total ∆G for this reaction is not changed by the presence of enzymes.
What does nucleoside diphosphate kinase do? Why is it important?
It converts an NDP to an NTP. Ie. GTP + ADP -> ATP + GDP. The various NTP pools are able to share available energy and avoid rate-limiting steps (eg. fleeing a predator). It allows a high-energy using reaction to continue in times of stress.
What inhibits ATP-generating pathways? What stimulates ATP-generating pathways?
They are inhibited by high levels of ATP and stimulated by high levels of ADP and/or AMP
What inhibits ATP-utilizing pathways? What stimulates ATP-utilizing pathways?
They are inhibited by high levels of ADP and/or AMP and stimulated by high levels of ATP.
Feedback inhibition usually occurs where in the pathway?
An early step in the pathways. The regulatory enzyme which turns a pathways on and off in response to energy state of the cell usually catalyzes an early step in the pathway.
The cell has a central pool of energy that can regulate (be sensed) by enzymes, why is this important?
It allows the cell to sense its energy levels and to regulate them appropriately.
How does creatinine kinase work to help a cell achieve short-term maintenance of ATP under sever energy stress?
It converts phosphocreatine + ADP -> creatine + ATP. It is found in vertebrate muscle and nerves. It is an ATP buffer allowing muscles to work longer.
How does adenylate kinase work to help a cell achieve short-term maintenance of ATP under sever energy stress?
It converts 2 ADP -> ATP + AMP. It keeps ATP levels up but raises AMP levels. It is ubiquitous to all animals.
How does adenylate deaminase work to help a cell achieve short-term maintenance of ATP under sever energy stress?
By removing AMP in the reaction, AMP + H20 -> IMP + NH3, it pulls the adenylate kinase reaction forward keeping the cell alive for a few more minutes. (It allows AK to make ATP from 2 ADP).
