Metabolism: Energy and Enzymes Chapter 6

Energy = the ability to do work Kinetic Energy - energy of motion Potential Energy - stored energy First Law of Thermodynamics - the law of conservation of energy Second Law of Thermodynamics - energy cannot be changed without a loss of usable energy (heat)

Metabolic Reactions Reactants  Products a + b  c + d Exergonic: releases energy Endergonic: absorbs energy

ATP - the energy currency of cells (adenosine triphosphate) Functions: 1. CHEMICAL WORK - Supplies energy needed to make macromolecules that make up the cell (and organism) 2. TRANSPORT WORK - Supplies energy needed to pump substances across the cell membrane 3. MECHANICAL WORK - supplies energy needed to make muscles contract and other cellular parts to move (flagella)

Metabolic Pathways & Enzymes (6-3) 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

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) Two types: 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 Quiz

Enzyme Lab(s) 2H 2 O > 2H 2 O + O 2 Hydrogen Peroxide is broken down by the enzyme: catalase within cells. KMNO4 (potassium permanganate) can be used to determine how much H 2 O 2 is left within the flask after the reaction has stopped. (Titration)

The more KMnO 4 you use, the more peroxide is left in the flask. You slowly add KMnO 4, which is purple, to the flask. The peroxide in the flask causes the KMnO 4 to lose color when the solution is mixed thoroughly. When all the peroxide has reacted with KMnO 4, any additional KMnO 4 will remain light brown or pinkish even after you swirl the mixture. This is the endpoint. Record the amount of KMnO 4 you have used.

The activity of catalase can be seen by the bubbling of oxygen during the reaction Generally speaking, catalase reactions occur faster at warmer temperatures. If temperature is too hot (boiling) then the enzyme becomes denatured

Virtual Labs with Enzymes McGraw Hill Lab Bio 114 Enzymes Lab Bench Enzyme Catalysis

Use the following vocabulary in your discussions Functional groupCarbon rings Carboxyl groupPhosphate group Amino groupEnzyme Hydroxyl groupSubstrate Double bondMonosaccharide Single bondDisaccharide C-C bondsFatty Acids Nucleic acidSteroids Protein Lipid Carbohydrate Amino Acid Nitrogen base