Metabolism: Energy and Enzymes

1. Metabolism: Energy and Enzymes

2. Energy • Ability to do work, change matter • Kinetic – energy in motion • Potential – stored energy • Chemical energy (food) • Mechanical energy (motion)

3. Thermodynamics • 2 Laws: • 1. Law of conservation of energy – Energy cannot be created or destroyed, but it can be changed from one form to another (heat energy) • 2. Energy cannot be changed from one form to another without a loss of usable energy. • When heat is released, it is not longer available to do work, lost to the environment. Cells are 40% efficient, rest of energy is given off as heat

4. Entropy • Used to indicate the relative amount of disorganization in universe • Every process that occurs in cells increases the total entropy of the universe. • More organized = less stable • Clean room, more organized but less stable than a messy room • entropy clip

5. Metabolic reactions • Metabolism • Reactants – products • Free energy – amount of available energy to do work after a chemical reaction has taken place (G) • Exergonic reactions – delta G is negative, products have less energy than the reactants, reaction is spontaneous, energy is released, ex. ATP breakdown • Endergonic reactions – delta G is positive and products have more free energy than the reactants. Can only take place if there is an input of energy.

6. Adenosine Triphosphate • Energy currency, universal, can be used in many different types of reactions. • Composed of Adenine (nitrogen base), ribose sugar and 3 phosphate groups • Uses of ATP • Chemical work – synthesize macromolecules • Transport work – pumps • Mechanical work – muscle contraction, cilia to beat, chromosomes to move.

7. Coupling reactions • Energy released by exergonic reactions drive endergonic reactions. • ATP breakdown is exergonic

8. Function of ATP • Chemical work – helps to synthesize macromolecules • Transport work – supplies energy for pumps across membrane • Mechanical work – supplies energy to do work, muscle contraction, cilia beat…

9. Chemical reactions • Reactants  products • Bonds broken and new ones formed • CO2 + H2O + light  C6H12O6 + O2 • Absorb or release energy • Water freezing – energy released • Ice melting – energy absorbed • metabolism

10. Enzyme activity • Activation energy is used to start chemical reactions • Biochemical reactions – reactions in cells • Enzyme – increase speed of chemical rxn • Catalyst – reduce activation energy of chem. Rxn • Homeostasis • Most are proteins • End in -ase • Different enzymes catalyze different chemical reactions ex. Lactase/lactose

11. Degradative reactions – substrate broken down Synthesis reaction – substrates combine, larger product Enzymes are not used up in the reaction, available to bind to another substrate. Active site – area on enzyme that the substrate binds to. Induced fit model- enzyme complex undergoes a slight change in shape

12. Enzyme substrate complex

13. Factors that affect enzyme activity • Temperature • pH • Can change shape of enzyme – denaturing • If enzyme changes, chemical reaction can not take place • Cofactors – non protein helpers • Inorganic - Zinc, iron, copper • Organic – called a coenzyme, vitamins

14. Enzyme inhibitors • Competitive inhibitors – mimic substrates and compete for active site, reduce productivity • Noncompetitive inhibitors – do not bind to active site, but the allosteric site • When bound, changes shape of active site • Toxins and poisons