Bioenergetics: The role of ATP (Chapter 11) Flashcards
What is Bioenergetics?
Study of Energy Change in Biochemical Processes
Define: Starvation
Depletion of energy resources
Define: Marasmus
Malnutrition due to energy deficiency
Define: Metabolic Rate
And what controls the Metabolic rate?
Rate of energy release.
Controlled by Thyroid Hormones
Define: Gibbs free energy(chemical potential)
The portion of energy which is available to do work. In other words:
- Useful energy.
What is the First Law of Thermodynamics?
The total energy of a system and it’s surroundings remains constant.
What is the Second Law of Thermodynamics?
With EVERY spontaneous reaction, there must be an INCREASE in Entropy.
What is an Exogonic Reaction?
Reaction which:
- has a negative Gibbs free energy change
- irreversible
- spontaneous
What is an Endogonic Reaction?
Reaction which:
- has a positive Gibbs free energy
What happens when the change in Gibbs Free Energy = 0
The reaction is at equilibrium
What is the conditions for “Standard Free Energy” in Biological Systems?
ph=7
What reaction is Anabolism, Catabolism?
Catabolism = Exogonic Rxns Anabolism = Endogonic Rxns
Catabolism + Anabolism = Metabolism
What is coupling?
What two types are there?
Advantage of one method over the other?
A endogonic reaction can be coupled to a exogonic reaction so that it is made possible.
Either can be done by:
1) Making a common obligatory Intermediate
- A+B = I = C + D
- Useful because it has an “inbuilt mechanism for control of oxidation”
- Useful in respiratory control as rate of utilisation of D controls rate of oxidation of B.
2) Synthesising a high energy potential compound
- this can then be incorporated into the endogonic reaction
Advantage:
-Compound of high energy potential does not need to be structurally related to reactant/produce.
Autotrophic vs Heterotrophic Organisms
Autotrophic:
- Obtain free energy from “simple exogonic processes”
- like sunlight
Heterotrophic:
- These couple their metabolism to breakdown of complex organic molecules in the environment.
Role of ATP in coupling?
How does ATP function as?
Transfers free energy from exogonic to endogonic reaction.
It functions as a Mg2+ complex.
Compare ATP, ADP and AMP in terms of energy
- ATP has two high energy anhydride bonds.
- ADP has one high energy anhydride bond
- AMP has one LOW energy ester bond.
What are:
- High Energy Phosphates?
- Low Energy Phosphates?
High Energy Phosphates:
-free energy change > ATP’s
-Usually:
- Anhydrides/ Endophosphates/ phosphoguanidines
Eg/
1,3 Bisphosphoglucerate, Creatine Phosphate, Arginine Phosphate, Phospoenolpyruvate
Low Energy Phosphates:
-Free energy change
Reason for High Free Energy change of ATP?
Due to :
- relief of charge of repulsion between adjacent negatively charged oxygen atoms
- stabilisation of reaction products (especially phosphate as a resonance hybrid…)
Uses of ATP?
1) Energy Currency
2) Donates phosphates for phosphorylation reactions
3) Precursor of cAMP
4) acts as a co-transmitter which acts on PURIGENIC Receptors
(something to do with gut relaxation, if we get asked this I’m going back to England and will live on welfare… without a degree, or any form of education. Fucking purigenic receptors, do they think this is physiology?)
Major Sources of High Energy Phosphates (source of ATP)
1) oxidative phosphorylation
2) Glycolysis - net formation of 2P
- catalysed by pyruvate kinase
3) Substrate level phosphorylation in Citric Cycle
- one P generated
4) Phosphagens
What does Adenylate Kinase (Myokinase) do?
- write the reaction and state what it is useful for?
-Interconverts Adenine Nucleotides.
AMP + ATP = 2ADP
It allows:
1) ADP to be used to synthesise ATP
2) AMP to be rephosphorylated to form ADP
3) When ATP concentration is down, AMP concentration increases, acting like a signal for more generation of ATP.
Role of ACYL-CoA Synthease
How is the reaction ensured to be irreversible? (write the equation).
Converts ATP directly to AMP when activating long chain fatty acids.
Reaction has loss of free energy.
Ensures irreversibility by:
- hydrolytic splitting of PPi
PPi + H20 -> 2Pi
Done by Inorganic Pyrophosphatase.
What does:
Nucleotide Diphosphate Kinase (NDP) do?
Write the equation.
NDP makes Nucleoside triphophates from their diphosphates.
ATP + NDP NTP + ADP
What does:
Nucleotide Monophosphate Kinase (NMP) do?
Nucleoside Monophophate makes Diphosphates from their monophosphates.
What are Phosphogens?
Name the ones found in vertebrates/Invertebrates?
How do they help in Muscle contraction?
They are:
- storage forms of high energy phopshates.
Vertebrates: Creatine Phosphate
Invertebrates: Arginine Phosphate
Allows maintenance of ATP during muscle contract because when ATP:ADP ratio increases, the concentration of phosphogens always increases.
