Metabolism: Energy and Enzymes Chapter 6

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 utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis 2.A.1: All living systems require constant input of free energy 2.A.2: Organisms capture and store free energy for use in biological processes 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization

First Law of Thermodynamics - the law of conservation of energy ~Energy cannot be created or destroyed Second Law of Thermodynamics - energy cannot be changed without a loss of usable energy (heat)

Metabolic Pathways & Enzymes Enzyme - protein molecule that functions as an organic catalyst to speed reactions Substrate - reactants in the enzymatic reaction, this is what an enzyme attaches to Energy of Activation = the energy required to cause the reaction

Properties of Enzymes: Enzymes are made of proteins. They speed up chemical reactions inside the cytoplasm. They are needed only in small amounts They remain unchanged after each reaction and can therefore be reused Each enzyme is specific for a substrate

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

Induced Fit Model - substrates and enzymes fit together like a lock and key.  (Degradation vs Synthesis)                  breaking down vs building

Factors Affecting Enzymatic Speed 1. Substrate concentration 2. Temperature & pH * 3. Enzyme concentration Enzymes can be denatured - they change shape so much that they are no longer effective. High temp or pH can cause denaturation. 

Siamese cats have an enzyme that works at lower temperatures only, causing the nose and ears to become a darker color than the rest of the body.

Enzymatic Inhibition - when a substance binds to an enzyme and decreases its activity. (Usually reversible) Competitive Inhibition  Noncompetitive Inhibition (allosteric site) **Both are forms of feedback inhibition

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

Enzyme Animation (Tutorial)  http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf Enzyme Quiz http://www.sciencegeek.net/Biology/review/U2Enzymes.htm

Enzyme Lab(s) 2H2O2 --------> 2H2O + O2 Hydrogen Peroxide is broken down by the enzyme: catalase within cells.    To determine the speed of a reaction you can either A) measure the amount of products produces (oxygen) B) measure the amount of substrate (hydrogen peroxide) is left over when the reaction is stopped

The activity of catalase can be seen by the bubbling of oxygen during the reaction

Virtual Labs with Enzymes McGraw Hill Lab