Introduction to Metabolism Energy & Enzymes Ms. Napolitano Honors Biology

11/22 – Do Now Please get your clickers! Think about and answer the following questions: What is energy? Why do we, as humans, need energy? What are some different types of energy? What is the 1 st and 2 nd Laws of Thermodynamics?

Metabolism Metabolism – total of all chemical reactions that take place within an organism Metabolic/biochemical pathway – series of chemical reactions, catalyzed by enzymes The product of one reaction becomes the reactant of the next reaction

Types of Metabolic Pathways Catabolic pathways – break down complex molecules into simpler molecules E released Anabolic pathways – build complicated molecules from simpler molecules E consumed

Physics Review Energy Kinetic Thermal Potential Chemical The Laws of Thermodynamics 1 st Law 2 nd Law

Chemical Reactions Absorb or Release Energy Exergonic reactions release free energy Activation Energy (Ea) is the E required to start the reaction

Chemical Reactions Absorb or Release Energy Identify A, B, C, D Endergonic reactions absorb free energy

Catalyst Catalyst – reduces the activation energy to speed up the chemical reaction Enzyme – catalytic protein Specific substrate binds to active site on enzymes... called induced fit Enzymes reduce Ea Reaction occurs, products are formed Enzyme can be reused

Enzyme-Substrate Complex

Effect of Enzymes on Reaction Rate

External Factors can Affect Enzyme Activity Factors that affect enzyme shape will affect its function Different enzymes have different optimal conditions

Adenosine Triphosphate (ATP) Unstable molecule E coupling uses exergonic process to power an endergonic process Mediates most E coupling by providing E to power cell work E coupled by transferring PO 4 - to another molecule (phosphorylated)

Cofactors Cofactors – non-protein helpers that bind to enzymes Inorganic vitamins Ex: Zn, Cu, Fe Coenzymes – organic cofactors Ex: Vitamins A, B 12, C

Cofactors

Enzyme Inhibitors Inhibitors prevent an enzyme from catalyzing a reaction Competitive inhibitors – block substances from entering active sites Noncompetitive Inhibitors – bind to another part of the enzyme, causing the enzyme to change shape and become inactive Regularly present to regulate activity

Allosteric Regulation Allosteric Regulation – controls metabolic pathways, so they are not always “on” or always “off” in enzymes without quaternary structure Activators – stabilize active site Inhibitors – stabilize inactive form of active site Cooperativity – amplifies enzyme activity (allows additional substrate) Feedback inhibition – the product binds to an enzyme early in the metabolic pathway inhibiting the enzyme

The chemical equation for cellular respiration is: C 6 H 12 O 6 + O 2  CO 2 + H 2 O + Energy This is an example of an anabolic process. F Which of the following statements is NOT correct? A metabolic pathway... A.Has an orderly sequence of reaction steps B.Is mediated by only one enzyme that starts it C.May be anabolic or catabolic D.All of the above are incorrect An enzyme... A.Is a protein B.Lowers the activation energy of a reaction C.Is destroyed by the reaction it catalyzes D.1 and 2

What happens to an enzyme when it denatures? A.The activation energy of the reaction is doubled B.The activation energy of the reaction is lowered C.It’s optimal conditions for temperature of the enzyme are doubled D.The shape of the enzyme molecule is changed The chemical equation for cellular respiration is: C 6 H 12 O 6 + O 2  CO 2 + H 2 O + Energy This is an example of an exergonic process. T