Metabolism: Energy and Enzymes

Energy = the ability to do work Kinetic Energy (energy of motion) | Potential Energy (stored energy) Energy is one of the BIG IDEAS in biology Biological systems (living things) utilize energy and molecular building blocks to grow, reproduce, and maintain homeostasis 2.A.1: All living systems require constant input of free energy (aka – food!) 2.A.2: Organisms capture and store free energy for use in biological processes (photosynthesis and respiration) 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization (eating, food webs, energy and biochemical cycling)

First Law of Thermodynamics - the law of conservation of energy ~REMEMBER: Energy cannot be created or destroyed Second Law of Thermodynamics - energy cannot be changed without a loss of usable energy (heat) ~When organisms convert food energy to life energy (motion, sound, etc), some energy is always lost as heat

Metabolism (use of energy in the body through chemistry) is driven by Enzymes Enzyme - protein molecule that functions as an organic catalyst to speed reactions Substrate – reactant(s) in the enzymatic reaction; what an enzyme works on Activation Energy = the energy required to start the reaction; enzymes work by lowering the AE

Properties of Enzymes: Enzymes are made of proteins. They speed up chemical reactions inside the cytoplasm. They are needed only in small amounts b/c they are reusable They remain unchanged after each reaction Each enzyme is specific for one substrate

Biology Pro-Tip Most enzyme names end in the letters -ase Ex: The enzyme that breaks down sucrose is ….. SUCRASE The enzyme that breaks down lactose (milk sugar) is… LACTASE

Enzyme Function Induced Fit – enzymes and their substrate(s) fit together like a lock and key.  - enzymes can degrade (break down) or synthesize (put together)

Factors Affecting Enzyme Rate (speed) 1. Substrate concentration: more substrate = higher rate 2. Temperature & pH *: enzyme specific; optimum temp and pH = highest rate; too far off optimum can lead to denaturing (changing the shape) of the enzyme so that it no longer functions 3. Enzyme concentration: more enzyme = higher rate Toothpick-ase demonstration . 

Fun example: Siamese cats have a hair color enzyme that works at lower temperatures only, causing the nose and ears (lower temp areas) to become a darker color than the rest of the body.

Controlling Enzymes Enzymatic Inhibition - when a substance binds to an enzyme and stops or slows its function. (Usually reversible) - Competitive Inhibition- mimics the substrate and blocks the active site (picture b) - Noncompetitive Inhibition (aka allosteric inhibition) – binds away from active site, but changes enzyme shape to stop reaction (picture c)

Note: Some inhibitors are NOT reversible - poisons like cyanide and lead all irreversibly affect enzymes QUESTION: What type of inhibition is pictured below?

Enzyme Animation (Tutorial)  http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf