Lecture on Energy and Metabolism

Introduction to Energy in Metabolism

• Importance of energy for macromolecule production from small molecules.
• Basic questions about energy and metabolism:
• Why do organisms eat?
• What happens without energy?
• Why do chemical reactions occur?
• Overview of universal laws of thermodynamics applied in cellular context.

First Law of Thermodynamics

• Conservation of Energy:
• Total energy in the universe is constant.
• Animals consume energy stored in molecular bonds, with energy conversion occurring.
• Energy, although converted and sometimes lost as heat, is not destroyed.
• Heat loss contributes to body temperature.

Second Law of Thermodynamics

• Entropy and Disorder:
• Total free energy in the universe declines, leading to increased disorder.
• Without energy input, cells and animals lose maintenance of biological order.
• Essential to maintain biological order and normal cellular function.

Energy Flow and Macromolecule Formation

• Energy conversion occurs in various forms, for example, light energy to chemical energy in plants.
• Photosynthesis and cellular respiration as reciprocal processes:
• Photosynthesis: water and carbon dioxide utilized, oxygen released.
• Cellular respiration: oxygen utilized, carbon dioxide released.

Chemical Reactions and Free Energy

• Overview of energetically favorable (catabolic) and unfavorable reactions (anabolic).
• Delta G (ΔG):
• Negative ΔG indicates spontaneous reaction (energetically favorable).
• Positive ΔG indicates non-spontaneous reaction (requires energy input).
• Example of ATP hydrolysis from three phosphates to two, releasing energy.

Oxidation and Reduction

• Oxidation: loss of electrons, energetically favorable reactions.
• Reduction: gain of electrons, energetically unfavorable processes.
• Importance in metabolism: reactions depend on coupling of oxidation (energy release) and reduction (energy input).

Coupled Reactions and Macromolecule Formation

• Energetically favorable reactions (oxidation) can provide energy for unfavorable reactions (reduction).
• ATP as a key molecule in energy transfer between catabolism and anabolism.

Activation Energy and Enzymatic Activity

• Concept of activation energy: energy needed to initiate a reaction, influenced by enzymes.
• Enzymes lower activation energy, coordinating metabolic pathways.

Activated Carrier Molecules

• Molecules like ATP that temporarily store energy from oxidation processes.
• Allow for separation of catabolism and anabolism in time and space.
• Examples of Activated Carriers:
• ATP: primary energy carrier, converting to ADP and releasing energy (approx. 13 kilocalories/mole).
• Nicotinamide adenine dinucleotide (NAD) and related compounds as electron carriers.
• Acetyl CoA as a common metabolic intermediate.

Summary of Enzymatic and Metabolic Processes

• Metabolism consists of catabolic (breaking down) and anabolic (building up) pathways.
• Understanding of energy flow enables predictions on cellular processes and metabolism efficiency.

Conclusion and Implications for Further Study

• Importance of coupling reactions in cellular metabolism.
• Future discussions will build on these fundamental ideas.