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Toothpickase Activity.pdfEnzymes lower the activation energy by enabling reactants to come together and react more easily.
Example: A molecule of sucrose in solution may hydrolyze in about 15 days; with sucrase present, the same reaction occurs in 1 second!
Enzymes are highly specific—each one catalyzes only one chemical reaction.
Reactants are substrates: they bind to specific sites on the enzyme—the active sites.
Specificity results from the exact 3-D shape and chemical properties of the active site.
Take notes throughout the lab and show me your lab quiz results when you are finished.
Enzymes use one or more mechanisms to catalyze a reaction:
- Inducing strain—bonds in the substrate are stretched, putting it in an unstable transition state.
- Substrate orientation—substrates are brought together so that bonds can form.
Adding chemical groups—R groups may be directly involved in the reaction.
Enzyme 3-D structures are so specific that they bind only one or a few related substrates.
Many enzymes change shape when the substrate binds.
The binding is like a baseball in a catcher’s mitt. The enzyme changes shape to make the binding tight—“induced fit.”
Some enzymes require ions or other molecules (cofactors) in order to function:
- Metal ions
- Coenzymes add or remove chemical groups from the substrate. They can participate in reactions with many different enzymes. It binds to the active site of the enzyme, adds or removes a chemical group from the substrate, and then separates from the enzyme to participate in other reactions. A coenzyme differs from a substrate in that it can participate in many different reactions with different enzymes.
- Prosthetic groups (nonamino acid groups) permanently bound to their enzymes.
Rates of catalyzed reactions:
- There is usually less enzyme than substrate present, so reaction rate levels off when all enzyme molecules are bound to substrate molecules.
- The enzyme is said to be saturated.
- Maximum reaction rate is used to calculate enzyme efficiency—molecules of substrate converted to product per unit time (turnover).
- Turnover ranges from 1 to 40 million molecules per second!
Vocabulary: Energy, Kinetic, Potential, Chemical, Heat, 1st Law of Thermodynamics, 2nd Law of Thermodynamics, Entropy, Metabolism, Reactants, Products, Free energy, Exergonic, Endergonic
Unit 3 Cellular Energetics (3).pptxCellular Energetics Notes.docxComplete this AP Biology Practice Enzyme FRQ.
Complete this AP Biology Practice Enzyme FRQ.
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