70 Questions
In a biochemical reaction, what does it mean if ΔG is positive?
The reaction proceeds only if free energy can be gained
If ΔG is zero in a system, what does it imply?
The system is at equilibrium and no net change takes place
What is the standard free energy change at a standard state with a pH of 7.0?
$ΔG0′$
How do vital processes such as synthetic reactions and active transport obtain energy?
By coupling to oxidative reactions
Why are the terms 'exergonic' and 'endergonic' preferred over 'exothermic' and 'endothermic' in biochemical contexts?
To indicate loss or gain of energy in any form, not just heat
What happens when the magnitude of ΔG in a system is great?
The system is stable with little or no tendency for a reaction to occur
What does the second law of thermodynamics state?
The total entropy of a system must increase if a process is to occur spontaneously.
How is entropy defined?
The total disorder of a system.
In biochemical reactions, what does ΔG represent?
Change in free energy
If ΔG is negative, what can be said about the reaction?
It proceeds spontaneously with loss of free energy.
What happens if ΔG is both negative and of great magnitude for a reaction?
The reaction goes virtually to completion and is essentially irreversible.
What is the relationship between ΔH, ΔE, and ΔS in biochemical reactions?
ΔH ≈ ΔE which is approximately equal to ΔS
What is the role of the high-energy compound denoted as ~Ⓔ in the living cell?
Serves as a transducer of energy from exergonic reactions to endergonic reactions
Which compound is identified as the principal high-energy intermediate in the living cell?
Adenosine triphosphate (ATP)
What is the source of free energy for autotrophic organisms?
Sunlight
What distinguishes heterotrophic organisms in terms of obtaining free energy?
They breakdown complex organic molecules
In what process is ATP crucial for maintaining living processes?
Biosynthesis
How does the high-energy compound ~Ⓔ facilitate energy transfer within the living cell?
Transduces energy from exergonic reactions to endergonic reactions
What is the role of ATP in biochemical reactions?
Promoting thermodynamically unfavorable reactions
Which enzyme interconverts adenine nucleotides to facilitate high-energy phosphate usage and AMP recovery?
Adenylyl Kinase (Myokinase)
What happens when ATP becomes depleted in a cell?
AMP concentration increases
In a reaction catalyzed by hexokinase, what allows the irreversible phosphorylation of glucose to proceed?
High-energy phosphate in ADP
What is the impact of coupling an exergonic reaction with an endergonic one?
The overall reaction becomes more favorable
Which reaction is more likely to be irreversible under physiological conditions?
$Glucose + P1 \rightarrow Glucose 6- phosphate$
What role does ATP play in organisms?
Mediating the transference of free energy from exergonic to endergonic processes
Which components make up ATP?
Adenine, ribose, and three phosphate groups
What is the bioenergetic significance of the free energy of hydrolysis of ATP?
It helps estimate the comparative tendency of phosphate groups to transfer to an acceptor
What characterizes low-energy phosphates in terms of their G0' values?
Their values are smaller than that of ATP
How do high-energy phosphates compare to ATP in terms of their G0' values?
Their G0' values are higher than that of ATP
What is the function of ATP in cellular reactions?
To store and transfer energy within the cell
In a coupled exergonic-endergonic system, what is the role of the endergonic process?
It must be a component of the coupled system.
What term is used to describe catabolic reactions in biologic systems?
Catabolism
What characterizes synthetic reactions that build up substances in biologic systems?
Anabolism
How can an exergonic and endergonic reaction be coupled in biologic systems?
By sharing a common obligatory intermediate.
Why is it essential for endergonic processes to be coupled with exergonic ones in biologic systems?
To achieve an overall net exergonic change.
What role does loss of free energy as heat play in the coupling of reactions in biologic systems?
It is crucial for the overall net exergonic change.
When ΔG is positive in a biochemical reaction, what does it indicate?
Free energy can be gained for the reaction to occur
In a biochemical system with a ΔG of zero, what state does the system reach?
Dynamic equilibrium
What is the significance of coupling exergonic and endergonic processes in biochemical reactions?
It leads to the release of free energy
In a biochemical context, what does the term 'exergonic' specifically imply about a process?
Loss of free energy
When reactants are present in concentrations of 1.0 mol/L, what does ΔG0 represent?
The standard free energy change
How is a biochemical system described when the magnitude of ΔG is considerable?
The system is stable with little tendency for reactions to occur
What is the primary role of ATP in living organisms?
Transferring free energy from exergonic to endergonic processes
How do high-energy phosphates, compared to low-energy phosphates, typically relate to the free energy of hydrolysis of ATP?
High-energy phosphates have G0' values higher than ATP
What bioenergetic significance does the free energy of hydrolysis of ATP hold?
It acts as a measure of energy released from the breakdown of ATP
What is a key difference between high-energy and low-energy phosphates?
High-energy phosphates release more energy upon hydrolysis
How does the ΔG0' value for the hydrolysis of the terminal phosphate of ATP relate to other biochemically important phosphates?
It is higher, indicating higher energy transfer potential
Why is ATP considered a crucial molecule for cellular processes?
For transferring free energy between exergonic and endergonic processes
Which enzyme catalyzes the interconversion of adenine nucleotides to facilitate high-energy phosphate usage and AMP recovery?
Adenylyl kinase (Myokinase)
Under physiological conditions, which reaction is more likely to be irreversible due to its high exergonic nature?
Phosphorylation of glucose
What is the bioenergetic significance of AMP increasing in concentration when ATP becomes depleted?
It acts as a metabolic signal to increase the rate of catabolic reactions
Which enzyme is responsible for the irreversible phosphorylation of glucose under physiologic conditions?
Hexokinase
What is the role of ATP in allowing the coupling of thermodynamically unfavorable reactions to favorable ones?
To provide energy for unfavorable reactions
Which compound's interconversion allows the recovery of AMP by rephosphorylation to ADP?
~Ⓔ (AMP)
What is the primary reason for the high free-energy change on hydrolysis of ATP?
Stabilization of the reaction products, especially phosphate, as resonance hybrids
In the context of high-energy compounds, which compound acts as an 'Energy Currency' in the cell?
Adenosine triphosphate (ATP)
What role do thiol esters, acyl carrier protein, and amino acid esters play in cellular processes?
Involved in protein synthesis
Which major energy source participates in the energy conservation or energy capture processes within the cell?
~℗
What happens at a rapid rate due to the extremely small total ATP/ADP pool within active tissues?
Consumption and regeneration of ATP via an ATP/ADP cycle
How does ADP participate in maintaining energy levels within the cell?
Accepts high-energy phosphate to form ATP
Where does the free energy come from in oxidative phosphorylation in aerobic organisms?
The respiratory chain oxidation using molecular O2 within mitochondria
How many nucleotides are formed as a result of glycolysis converting one molecule of glucose to lactate?
Two
Where is creatine phosphate primarily found as a storage form of high-energy phosphate?
Skeletal muscle, heart, spermatozoa, and brain
What is generated directly at the succinate thiokinase step in the Citric Acid Cycle?
High-energy phosphate
Which compound acts as the 'Energy Currency' of the cell by allowing the coupling of thermodynamically unfavorable reactions to favorable ones?
Creatine phosphate
What allows ATP concentrations to be maintained during rapid energy utilization for muscular contraction?
Phosphagens
Which process involves the transfer of high-energy phosphate between ATP and creatine?
Oxidative phosphorylation
Which enzyme catalyzes the formation of lactate from glucose in glycolysis?
Pyruvate kinase
What is the net amount of ATP generated from glycolysis when converting glucose to lactate?
2 ATP molecules
Where does arginine phosphate primarily occur as a storage form of high-energy phosphate?
Skeletal muscle, heart, spermatozoa, and brain
Explore the biologic advantage of ATP as a transducer of energy from exergonic to endergonic reactions or processes like biosynthesis, muscular contraction, nervous excitation, and active transport.
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