Metabolism 8.1

Essential Idea: Metabolic reactions are regulated in response to the cell’s need. 8.1 Metabolism Understandings: Metabolic pathways consist of chains and cycles of enzyme-catalyzed reactions   Enzymes lower the activation energy of the chemical reactions that they catalyze Enzyme inhibitors can be competitive or non-competitive Metabolic pathways can be controlled by end-product inhibition Applications: End-product inhibition of the pathway that coverts threonine to isoleucine Use of databases to identify potential new anti-malarial drugs Skills: Calculate and plot rates of reaction from raw experimental results Distinguish different types of inhibition from graphs at specified substrate concentration

Metabolism Sum of all chemical reactions in a body Anabolic Catabolic Build complex molecules Break down complex molecules Endergonic Exergonic Biosynthetic Degradative Photosynthesis Cellular respiration

Metabolic pathways catalyst Occurs in specific compartment of cell Most reactions are sequence of events

Induced fit model – enzyme undergoes change in conformation as it interacts with substrate Still requires proper shape of enzyme and substrate Enzyme is undergoing conformational change Change in R groups of A.A. upon interaction with substrate Complex high level proteins Active site

Enzymes work by lowering activation energy (AE) AE is the energy required to destabilize existing bonds Enzyme reduce energy needed to break/change bonds DO NOT change amount of product formed

Mechanism of enzyme action repeat Enzyme changes shape to fit substrate and enzyme-substrate complex forms AE is lowered, atoms are rearranged, product is released Surface of substrate Contacts active site E + S  ES  E + P

Competitive Inhibition Similar structure Competitive Inhibitors – a molecule binds into the active site, blocking access to the substrate Decrease rate in reaction Examples: Sulfanilamide  blocks PABA – prevents production of folic acid in bacteria Can be reversible or irreversible If reversible, can be overcome by increasing substrate concentration

Non-competitive Inhibition Non-competitive Inhibitors – bind elsewhere on enzyme and forces change in shape of active site allosteric inhibition Distorted active site no longer allows substrate to bind Examples: Metallic ions (Hg) Allosteric inhibitor leaves – enzyme becomes functional again

End Product Inhibition Shut down Used to regulate metabolic pathways Final product acts as an allosteric inhibitor to the first enzyme in the series Low product amount, allosteric inhibitor leaves and process resumes Enough product made