Chapter 8 THE ENERGY OF LIFE

 Energy is neither created nor destroyed  Entropy increases throughout time LAWS OF THERMODYNAMICS

 Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. THE ENERGY OF LIFE

FREE ENERGY

 Enzymes facilitate metabolic pathways FREE ENERGY

Chapter 8 ENZYMES

 Non biological reactions use heat as a catalyst  Biological reactions use enzymes  Enzymes: Speed up reactions  Heat would trigger all reactions in a cell  Destroy macromolecules ENZYMES

 The most structurally sophisticated molecules ENZYMES ARE PROTEINS

 Metabolic reactions are usually not spontaneous  Initial investment of energy to start a reaction  Enzymes lower the Ea of a reaction START THE REACTION

 Every enzymes is substrate specific!  Induced Fit: enzyme changes shape  Substrate is broken down or built up MIDDLE OF THE REACTION Hexokinase (a) without (b) with glucose substrate e_mechanism.html

 Enzymes are not used up in the reaction END THE REACTION

 Amylase:  in your mouth breaks down sugar  Peptidase  in your stomach break down proteins  Lipase:  in your small intestine break down lipids  ~2000 enzymes in your body working right now!!! COMMON ENZYMES IN YOUR BODY

REGULATING ENZYMES

 Heat: Denatures enzymes  pH: Acids or bases denature enzymes ENVIRONMENTAL EFFECTS

HEAT

PH

 Competitive  Similar in shape and attach to active site disabling the enzyme  Noncompetitive  Bind to allosteric site of the enzyme altering the shape of the active site INHIBITORS

 Nonprotein helpers for enzyme-substrate complex COFACTORS

 The product of a metabolic pathway may bind to the allosteric site and turn off the enzyme FEEDBACK INHIBITION