Introduction to Metabolism

1. Introduction to Metabolism How the Universe Really Works

2. What is Energy? • Capacity to do work • Forms of energy • Electrical • Mechanical • Chemical • Light • Heat

3. What is Energy? • Capacity to do work • Forms of energy • Potential energy • Kinetic energy

4. Kinetic and potential energy: dam • Stored Water = Potential Energy • Moving Water = Kinetic Energy

5. Kinetic and potential energy: cheetah at rest and running • Cheetah resting = Cheetah running = Potential Energy Kinetic Energy

6. Energy can be converted from one form to another. • As the boy climbs the ladder to the top of the slide he is converting his kinetic energy to potential energy. • As he slides down, the potential energy is converted back to kinetic energy. • It was the potential energy in the food he had eaten earlier that provided the energy that permitted him to climb up initially. Fig. 6.2

7. One-Way Flow of Energy • The sun is life’s primary energy source • Producers trap energy from the sun and convert it into chemical bond energy • Allorganisms use the energy stored in the bonds of organic compounds to do work

8. What Can Cells Do with Energy? • Energy inputs become coupled to energy-requiring processes • Cells use energy for: • Chemical work • Mechanical work • Electrochemical work

9. Energy Relationships large energy-rich molecules (fats, complex carbohydrates, proteins, nucleic acids) ADP + Pi BIOSYNTHETIC PATHWAYS (ANABOLIC) DEGRADATIVE PATHWAYS (CATABOLIC) simple organic compounds simple sugars, amino acids, fatty acids, nucleotides ATP energy-poor products such as carbon dioxide, water ENERGY INPUT

10. Thermodynamics • Thermodynamics is the study of energy transformations. • system indicates the matter under study and the surroundings are everything • closed systemis isolated from its surroundings. • In an open system energy (and often matter) can be transferred between the system and surroundings. • Organisms are open systems. • They absorb energy - light or chemical energy in organic molecules - and release heat and metabolic waste products

11. First Law of Thermodynamics • The total amount of energy in the universe remains constant • Energy can undergo conversions from one form to another, but it cannot be created or destroyed

12. Second Law of Thermodynamics • No energy conversion is ever 100 percent efficient • The total amount of energy is flowing from high-energy forms to forms lower in energy

13.  Two laws of thermodynamics • Conversion of energy from chemical potential to kinetic mechanical energy. • Some energy is lost to heat.

14. Entropy • Measure of degree of disorder in a system • The world of life can resist the flow toward maximum entropy only because it is resupplied with energy from the sun

15. Free Energy • Free energy can be thought of as a measure of the stability of a system. • Systems that are high in free energy - compressed springs, separated charges - are unstable and tend to move toward a more stable state - one with less free energy. • Systems that tend to change spontaneously are those that have high energy, low entropy, or both. • In any spontaneous process, the free energy of a system decreases.

16.   Energy changes in exergonic and endergonic reactions

17. The Math • We can represent this change in free energy from the start of a process until its finish by: • delta G = G final state - G starting state • Or delta G = delta H - T delta S • For a system to be spontaneous, the system must either give up energy (decrease in H), give up order (decrease in S), or both. • Delta G must be negative. • The greater the decrease in free energy, the greater the maximum amount of work that a spontaneous process can perform. • Nature runs “downhill”.

18. Still Calculating • The magnitude of delta G for an exergonic reaction is the maximum amount of work the reaction can perform. • For the overall reaction of cellular respiration: • C6H12O6 + 6O2 -> 6CO2 + 6H2O • delta G = -686 kcal/mol • Through this reaction 686 kcal have been made available to do work in the cell. • The products have 686 kcal less energy than the reactants

19. Endergonic Reactions • Energy input required • Product has more energy than starting substances product with more energy (plus by-products 602 and 6H2O) ENERGY IN 6 12

20. Exergonic Reactions • Energy is released • Products have less energy than starting substance energy-rich starting substance ENERGY OUT + 602 6 6 products with less energy

21. Energy Carriers Enzymes Cofactors Participants in Metabolic Pathways • Substrates • Intermediates • End products