Endergonic

Definition

Endergonic refers to a type of chemical reaction that absorbs energy from its surroundings, resulting in a positive change in Gibbs free energy ($$\Delta G > 0$$). These reactions are non-spontaneous, meaning they require energy input to proceed. Understanding endergonic reactions is crucial for grasping how energy flows in biochemical processes and the role of Gibbs free energy in determining reaction spontaneity.

5 Must Know Facts For Your Next Test

1. In endergonic reactions, the system gains energy, which can come from various sources such as heat or light.
2. These reactions often occur in biological systems, like photosynthesis, where energy from sunlight is absorbed to convert carbon dioxide and water into glucose.
3. The positive Gibbs free energy change indicates that the products of an endergonic reaction are less stable than the reactants.
4. Endergonic reactions are essential for processes like muscle contraction and the synthesis of complex molecules.
5. Energy coupling is a key concept where endergonic reactions are driven by the energy released from exergonic reactions in biological systems.

Review Questions

• How do endergonic reactions differ from exergonic reactions in terms of Gibbs free energy and spontaneity?
  • Endergonic reactions have a positive change in Gibbs free energy ($$\Delta G > 0$$), which means they absorb energy and are non-spontaneous. In contrast, exergonic reactions have a negative change in Gibbs free energy ($$\Delta G < 0$$), releasing energy and occurring spontaneously. This difference is crucial for understanding how energy is managed in chemical processes.
• Discuss the role of endergonic reactions in biological systems, providing examples of where they occur.
  • Endergonic reactions play a vital role in biological systems by facilitating processes that require an input of energy. For instance, photosynthesis is an endergonic reaction where plants absorb sunlight to convert carbon dioxide and water into glucose. Similarly, the synthesis of ATP from ADP and inorganic phosphate is another example, as it requires energy input to form high-energy bonds essential for cellular activities.
• Evaluate the concept of energy coupling in the context of endergonic and exergonic reactions, explaining how it supports cellular functions.
  • Energy coupling is a process where the energy released from exergonic reactions is used to drive endergonic reactions. This mechanism is vital for maintaining cellular functions because it ensures that necessary biochemical processes can occur despite their non-spontaneous nature. For example, ATP hydrolysis (an exergonic reaction) provides the energy needed for various endergonic processes like muscle contraction and biosynthesis, showcasing how cells efficiently manage energy to sustain life.

Related terms

Exergonic: Exergonic reactions release energy and have a negative change in Gibbs free energy ($$\Delta G < 0$$), making them spontaneous.

Gibbs Free Energy: A thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure.

Activation Energy: The minimum amount of energy required to initiate a chemical reaction, influencing the rate of both endergonic and exergonic reactions.