Lecture Notes: Basics of Reactions, Enzymes, and Metabolism

Introduction

• New Chapter Focus:
  • Basics of how reactions happen
  • Function and importance of enzymes
  • Construction of macromolecules in cells
• Lecture Structure:
  • How energy is used by cells and cell organization
  • Free energy, catalysis by enzymes
  • Activated carriers, biosynthesis, and ATP's role in metabolism

Overview

• Metabolism in Focus:
  • Three chapters focusing on metabolism and metabolic reactions
  • Analysis at a molecular level in upcoming lectures

Enzymes and Enzyme Kinetics

• Role of Enzymes:
  • Proteins that accelerate chemical reactions
  • Enable reactions to occur at physiological temperatures
  • Provide specific environments for reactions to occur
• Enzyme Catalysis:
  • Part of signaling and metabolic pathways
  • Highly specific for substrates
• Metabolism:
  • Controlled by reaction rates inside cells
  • Catabolic: Breaking down molecules to release energy
  • Anabolic: Building molecules, requiring energy input

Biological Order and Thermodynamics

• Maintaining Order:
  • Living organisms maintain order by creating environmental disorder
  • First Law of Thermodynamics: Energy conservation
  • Second Law of Thermodynamics: Increasing entropy
• Energy Conversion:
  • Plants convert light energy into chemical bonds
  • Organisms convert chemical bond energy into heat or ATP

Photosynthesis and Cellular Respiration

• Photosynthesis:
  • Conversion of CO2 and H2O into glucose and O2 using sunlight
• Cellular Respiration:
  • Breakdown of glucose into CO2 and H2O to release energy

Redox Reactions

• Oxidation and Reduction:
  • Electron transfer between molecules
  • Carbon compounds undergo oxidation (losing H, gaining O)

Enzyme Function

• Enzyme Role in Reactions:
  • Lower activation energy for spontaneous reactions
  • Do not initiate non-spontaneous reactions

Free Energy and Reaction Coupling

• Free Energy Change (ΔG):
  • Determines reaction spontaneity
  • Negative ΔG: Spontaneous reaction
  • Positive ΔG: Non-spontaneous reaction, requires coupling
• Reaction Coupling:
  • Link spontaneous with non-spontaneous reactions to enable them

Enzyme Kinetics and Inhibition

• Michaelis-Menten Kinetics:
  • Relationship between reaction rate and substrate concentration
  • Enzyme saturation at high substrate concentrations
• Inhibitors:
  • Competitive and non-competitive inhibitors affect enzyme activity

Activated Carriers and Biosynthesis

• ATP:
  • Primary energy carrier in cells
  • Phosphate bond hydrolysis releases energy for cellular work
• Other Carriers:
  • NADH, NADPH: Electron carriers
  • Acetyl CoA: Energy carrier in macromolecule synthesis

Summary

• Reactions and Energy:
  • Biological order maintained by releasing heat to environment
  • Enzymes catalyze reactions by lowering activation energy
  • Free energy change and equilibrium constants determine reaction feasibility
• Biosynthesis:
  • Activated carriers fuel anabolic pathways
  • ATP, NADH, NADPH, and acetyl CoA crucial for cellular processes

Next Lecture Preview

• Topic: How cells obtain energy from food
• Focus: Breakdown and utilization of sugars and fats to regulate metabolism