Lecture Notes on Energy in Cells

Introduction

• Energy Use in Cells: Essential for maintaining organization and life.
  • Comparison to household tasks: Cleaning requires energy, similar to cells needing energy to maintain order.
• Key Topics: Membranes, energy storage, and laws of thermodynamics.

Core Concepts

Membranes

• Separate inside from outside of the cell.
• Integral to the organization and function of cells.

Energy and Work

• Cells require energy to perform work and maintain order.
• ATP (Adenosine Triphosphate): The energy currency of the cell.
  • Structure: Adenine, ribose, and three phosphate groups.
  • Conversion: ATP ⇌ ADP + P (energetic transactions)

Metabolism

• Metabolism: Series of energy-transferring reactions.
  • Anabolic Reactions: Building large molecules from small subunits, require energy (e.g., forming proteins from amino acids).
  • Catabolic Reactions: Breaking down molecules to harvest energy (e.g., glycolysis, citric acid cycle).

Thermodynamics

First Law of Thermodynamics

• Conservation of energy: Energy cannot be created or destroyed, only transformed.
• Cells transform chemical energy into cellular energy (e.g., from sugars to ATP).

Second Law of Thermodynamics

• Entropy: Energy transformations are not 100% efficient, some energy is lost to disorder.

Energy Types

• Kinetic Energy: Energy of motion.
• Potential Energy: Stored energy, e.g., energy stored in chemical bonds.
• High Energy Molecules: High potential energy, easily release energy (e.g., ATP).

Chemical Reactions

• Forward and Reverse Reactions: Occur simultaneously, but cells control to favor energy harvesting.
• Enzymes: Control reaction direction and rate.
• Equilibrium: Balance between forward and reverse reactions.
  • Cells maintain a non-equilibrium state for energy production.

Energy and Metabolism

• Glycolysis: Breakdown of glucose for energy.
  • Phosphorylation of glucose keeps intracellular concentration low, maintaining influx.

Gibbs Free Energy

• Delta G: Change in free energy during a reaction.
  • Formula: ΔG = ΔH - TΔS
    • ΔH: Total energy
    • T: Temperature
    • ΔS: Entropy/disorder

Summary

• Energy is essential for cell function and organization.
• Energy transformations in cells are governed by thermodynamics.
• ATP is crucial for energy transfer.
• Cells utilize complex reactions, including metabolism and enzyme regulation, to harness and control energy efficiently.

---

Study Tips: Focus on understanding how ATP functions as an energy carrier and the significance of metabolic pathways in energy transformation. Review laws of thermodynamics and their implications in biological systems. Familiarize yourself with the structure and role of enzymes in regulating cell metabolism.