3.2 ATP: Energy Currency of the Cell Flashcards
What is ATP, and why is it important for cells?
ATP (adenosine triphosphate) is the universal energy currency of the cell, used by all organisms to power energy-driven actions such as mechanical, transport, and chemical work.
Why does ATP have a large amount of free energy?
ATP has a large amount of free energy due to the instability of the phosphate bonds. Hydrolysis of ATP releases about 31 kJ/mol of free energy, which is used in energy-requiring reactions.
What is hydrolysis of ATP?
Hydrolysis is the breaking of ATP’s terminal phosphate bond, resulting in ADP (adenosine diphosphate), inorganic phosphate (Pi), and the release of energy.
What are the three main functions of ATP in cells?
Chemical work: Energy for synthesizing macromolecules.
Transport work: Energy for membrane pumps.
Mechanical work: Energy for muscle contraction, cilia, and flagella movement.
Give an example of an energy-coupling reaction.
The conversion of glutamic acid and ammonia to glutamine is endergonic and non-spontaneous. When coupled with ATP hydrolysis, the reaction becomes exergonic and can proceed.
What is phosphorylation in cellular reactions?
Phosphorylation is the process where a phosphate group is transferred from ATP to another molecule, making that molecule more reactive and increasing its free energy.
What is the purpose of coupling reactions in metabolism?
Coupling uses energy from catabolic reactions (exergonic) to drive anabolic reactions (endergonic), allowing processes that would not proceed on their own to occur.
How is ATP regenerated in cells?
ATP is regenerated by combining ADP and inorganic phosphate (Pi) in an endergonic process, which requires free energy supplied by catabolic reactions in the mitochondria.
What is the ATP cycle?
The ATP cycle refers to the constant breakdown of ATP into ADP (exergonic) to provide energy for reactions, and the synthesis of ATP from ADP and Pi (endergonic) using energy from catabolic pathways.
What is activation energy?
Activation energy is the minimum amount of energy required to start a chemical reaction by rearranging chemical bonds in the reactants.
Why do cells use ATP instead of other molecules?
ATP is easily accessible, releases a manageable amount of energy, can couple with many different reactions, and can be produced using a variety of nutrients.
How do enzymes lower activation energy?
Enzymes lower activation energy by stabilizing the transition state, bringing substrates together in the correct orientation and proximity, and forming enzyme-substrate complexes.
Why can thermal energy be problematic for reactions?
Thermal energy can destroy macromolecules by damaging their structure, speeding up all reactions in a cell, including those not meant to occur quickly, leading to potential loss of function.
What is an enzyme-substrate complex?
An enzyme-substrate complex forms when an enzyme binds to its substrate, reducing the energy needed for the reaction to occur and facilitating product formation.
What are catabolic and anabolic reactions in terms of energy?
Catabolic reactions: Break down complex molecules and release energy (exergonic).
Anabolic reactions: Build complex molecules from simpler ones and require energy (endergonic).
