Chemical reactions and Enzymes 1 Certain chemical substances
Chemical reactions and Enzymes 1
• Certain chemical substances • (catalysts) reduce the amount of activation energy required Biological catalysts are called enzymes
• Enzymes are an important class of catalysts in living organisms – Mostly protein – Thousands of different kinds – Each specific for a different chemical reaction – Usually end in –ase (catalase, sucrase, lactase)
Enzyme Structure • Enzymes work on substances called substrates • Substrates must fit into a place on an enzyme called the active site • Enzymes are reusable! They are not permenantly changed in a reaction.
How do enzymes Work? Enzymes work by weakening bonds which lowers activation energy 5
Enzyme-Substrate Complex The structure formed when an enzyme bonds with its substrate is called the enzyme-substrate complex Substrate Joins Enzyme 6
Active Site • A restricted region of an enzyme molecule which binds to the substrate Active Site Substrate Enzyme 7
Induced Fit • A change in the shape of an enzyme’s active site • Induced by the substrate 8
Induced Fit • A change in the configuration of an enzyme’s active site (H+ and ionic bonds are involved). • Induced by the substrate Active Site Enzyme induced fit 9
What Affects Enzyme Activity? • 1. Environmental Conditions (p. H and Temperature) 2. Cofactors and Coenzymes 3. Enzyme Inhibitors 10
1. Environmental Conditions 1. Extreme Temperature are the most dangerous - high temps may denature (unfold) the enzyme. 2. p. H (most like 6 - 8 p. H near neutral) 3. Ionic concentration (salt ions) 11
2. Cofactors and Coenzymes • Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity • Example: Iron must be present in the quaternary structure - hemoglobin in order for it to pick up oxygen. 12
Two examples of Enzyme Inhibitors a. Competitive inhibitors: are chemicals that resemble an enzyme’s normal substrate and compete with it for the active site Substrate Competitive inhibitor Enzyme 13
Inhibitors b. Noncompetitive inhibitors: Inhibitors that do not enter the active site, site but bind to another part of the enzyme causing the enzyme to change its shape, shape which in turn alters the active site Substrate active site altered Enzyme Noncompetitive Inhibitor 14
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