20 Questions
In the ATP/ADP cycle, ATP can act as a donor of low-energy phosphate to compounds above it in the table.
False
What is the role of ATP in cellular metabolism?
ATP powers anabolic reactions, active transport of molecules and ions across membranes, and other energy-intensive processes such as muscle contraction.
The flow of electrons can do work in the cell, just like _______________________ transfer.
phosphate
What is the term used to describe the potential difference between two half-cells?
Electromotive force (emf)
Match the terms with their descriptions:
Oxidizing agent = Electron acceptor Reducing agent = Electron donor GER = Gain electrons, Reducing LEO = Lose electrons, Oxidizing
What is the direction of electron flow in redox reactions?
Electrons flow from a reducing agent to an oxidizing agent.
What is the purpose of maintaining a high ATP concentration in the cell?
To drive unfavorable reactions
The free energy release of ATP hydrolysis is lower inside the cell than in standard conditions.
False
What is the purpose of ATP in cellular metabolism?
ATP drives unfavorable reactions through the coupling of group transfer (phosphoryl, pyrophosphoryl, or adenylyl) to a substrate or enzyme.
The three phosphates of ATP are susceptible to ________________ attack.
nucleophilic
Match the following terms with their descriptions:
Phosphoryl Group = Type of group transfer Pyrophosphoryl Group = Type of group transfer Adenylyl Group = Type of group transfer ATP Hydrolysis = Energy-releasing reaction
What is the equation for calculating ΔGp?
ΔGp = ΔG´° + RT ln ([ADP][Pi] / [ATP])
What is the major energy currency of the cell?
ATP
The standard free energy of hydrolysis of ATP is -30.5 kJ/mol under all cellular conditions.
False
What is the process by which ATP is "earned" or "produced" in the cell?
Exergonic reactions
The hydrolysis of ATP involves the transfer of a _______________________ group.
phosphoryl
Match the following components of ATP with their descriptions:
A = Ribonucleotide B = Energy currency of the cell C = Product of ATP hydrolysis D = Resonance hybrid
What is the result of the hydrolysis of ATP in terms of pH?
Decrease in pH
What is the term for the actual free energy of hydrolysis of ATP under intracellular conditions?
∆Gp
ATP is "spent" or "consumed" in exergonic reactions.
False
Study Notes
ATP (Adenosine Triphosphate)
- ATP is the major energy currency of the cell, earned in exergonic reactions and spent in endergonic reactions via hydrolysis.
- ATP connects catabolism and anabolism.
- Components of ATP include:
- Adenine
- Ribose
- Triphosphate (three phosphate groups)
ATP Hydrolysis
- ATP hydrolysis is a reaction where ATP is broken down into ADP and Pi.
- During hydrolysis:
- Charge separation occurs, relieving electrostatic repulsion.
- Pi is stabilized by formation of a resonance hybrid.
- ADP2- immediately ionizes at pH 7, releasing a proton into the medium and lowering pH.
- Products (Pi and ADP) have a greater degree of solvation relative to ATP.
Phosphorylation Potential, ∆Gp
- The standard free energy of hydrolysis of ATP is -30.5 kJ/mol.
- In the cell, the actual free energy of hydrolysis of ATP (ΔGp) differs from the standard free energy change due to unequal concentrations of ATP, ADP, and Pi.
- ΔGp can be calculated using the equation: ∆Gp = ∆G´°+ RT ln ([ADP][Pi] / [ATP])
ATP Donates Phosphoryl, Pyrophosphoryl, and Adenylyl Groups
- Each of the three phosphates of ATP is susceptible to nucleophilic attack.
- ATP drives unfavorable reactions not by harnessing the energy of hydrolysis but rather through the coupling of group transfer to a substrate or enzyme.
- ATP can act as a donor of high-energy phosphate to compounds below it in the table.
- ADP can accept high-energy phosphate to form ATP from compounds above it in the table, forming an ATP/ADP cycle.
Cellular Roles of ATP
- ATP powers anabolic reactions through group transfer reactions.
- ATP powers active transport of molecules and ions across membranes.
- ATP powers other energy-intensive processes such as muscle contraction.
Biological Reduction-Oxidation Reactions
- Reducing agent: oxidation happens, loses electrons.
- Oxidizing agent: reduction happens, gains electrons.
- The flow of electrons can do work in the cell, just like phosphate transfer.
- Electrons flow from a reducing agent to an oxidizing agent due to their different electron affinities, which is called the electromotive force (emf).
- Redox reactions can be described as Half-reactions (GER-LEO).
Learn about Adenosine Triphosphate (ATP), the energy currency of cells, and its breakdown into ADP and Pi through hydrolysis. Understand the components of ATP and its role in connecting catabolism and anabolism.
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