DS

lecture 2

Energy and Its Transformation

  • Energy Change & Capacity

    • Importance of transformation of energy in reactions.
    • Energy is seen as a capacity for change.
    • Major focus: How energy changes forms, especially in biological systems.

  • Conservation of Energy

    • Energy exists in different forms and can be described in terms of movement.
    • Especially relevant in cellular functions.
    • Energy is conserved, and excess energy is trapped for use in other reactions.

Types of Energy

  • Potential Energy

    • Defined as the capacity for something to change its energy status.
    • Example: A ball at the top of a hill has high potential energy, which converts to kinetic energy as it rolls down.
    • At the bottom of a hill, the energy is often transformed into heat.

  • Kinetic Energy

    • Energy of motion; as the ball rolls down, potential energy is converted to kinetic energy.
    • The basics of physics relate to how these energy transformations occur.

Thermodynamics

  • Definition of Thermodynamics

    • "Thermo" refers to energy; "dynamic" pertains to change.
    • Study of how energy changes form and the rules governing these changes.

  • Laws of Thermodynamics

    • First Law: Energy in the universe is fixed; it can neither be created nor destroyed, only transformed.
    • Example: In an atomic bomb, energy is released when an atom is split; it exists already within the atom.

  • Second Law:

    • Entropy increases; not all energy transformations are 100% efficient.
    • When energy changes form, some energy is transformed into heat or other forms, contributing to overall entropy in the system.
    • Practical Example: When hitting a table, kinetic energy converts to sound and heat energy, demonstrating energy transfer but not loss.

Biological Reactions and Energy Transfer

  • Closed vs Open Systems

    • Open System: Energy and matter can be exchanged with surroundings (e.g., explosion scenario).
    • Cells generally function as closed systems; energy exchange is less straightforward but crucial for biochemical reactions.

  • Metabolic Processes

    • Metabolic reactions create order from disordered materials.
    • Example: mRNA is transcribed from nucleotides; it becomes more organized through subsequent processing into functional proteins.

Gibbs Free Energy (B4G)

  • Definition

    • Gibbs free energy measures the change in energy during chemical reactions: B4G = G(final) - G(initial).
    • Determines whether a reaction can occur spontaneously (negative B4G) or whether energy must be input (positive B4G).

  • Interpretation

    • A reaction with a negative B4G has excess energy available, deemed spontaneous.
    • A reaction with positive B4G requires energy input, known as endergonic.

  • Energy Coupling in Reactions

    • Reactions often couple, allowing energy-releasing processes (exergonic) to fuel energy-consuming reactions (endergonic).
    • Example: ATP hydrolysis (exergonic) powers various cellular processes (endergonic).

Exergonic vs Endergonic Reactions

  • Exergonic Reactions

    • Have negative B4G; give off energy.
    • Example occurs in ATP hydrolysis.

  • Endergonic Reactions

    • Have positive B4G; require energy input.
    • Example includes the synthesis of glutamine from glutamic acid.

  • Coupled Reactions

    • Coupling allows endergonic reactions to proceed by using the energy released from exergonic reactions.
    • Example: ATP phosphorylation is used to couple glutamic acid synthesis (endergonic) with energy release from ATP hydrolysis (exergonic).

Practical Examples and Implications

  • Living Systems and Energy

    • Living systems exist at equilibrium through continuous energy exchanges and metabolic cycles.
    • Importance of energy transformation highlights biological organization and homeostasis.

  • Energy Efficiency

    • All reactions exhibit entropy; understanding energy change is crucial in biology.
    • Energy transformations in living organisms maintain function and metabolic homeostasis.

  • Concepts of Animation and Learning

    • Learners encouraged to engage, ask questions, and overcome conceptual barriers in understanding energy dynamics in biological systems.

  • Chinese Terms in Biology

    • Understanding of exergonic and endergonic reactions alongside thermal concepts, enabling effective learning in chemistry.

  • Conclusion

    • Study of energy transformation is fundamental in understanding biological processes, impacting fields such as physics, chemistry, and cellular biology.