Enzymes
Enzymes (Image from: http://www-news. uchicago. edu/releases/06/061011 proteins produced by cells biological catalysts speed up chemical reactions without being consumed This enzyme is the insulin-degrading enzyme, control of which might help to sure Alzheimer’s disease.
Activation Energy (EA) (Image from: http://drmccarthysciencehgms all chemical reactions require an initial input of energy, called activation energy (EA) Recall collision theory from Grade 10 Science
Enzymes and EA (Image from: http://www. glogster. com/glog. php
Activation Energy enzymes increase the rate of a reaction by lowering the activation energy (EA) How?
What are enzymes? enzymes are globular proteins that act on substrates (reactants) substrates bind to specific sites (active sites) on enzymes, creating the enzyme-substrate complex
Enzyme-Substrate Complex (Image from: http://kentsimmons. uwinnipeg
Induced-Fit Model (Image from: http://chsweb. lr. k12. nj in the “induced-fit” model, the enzyme alters shape to better “fit” substrate “lock and key” model Interactions between functional groups of enzyme & substrate cause enzyme to alter shape to better fit substrate
And then what? weak bonds form between substrate and enzyme enzyme provides proper orientation of substrate(s) enzyme puts strain on bonds of substrate(s), making them easier to break
Example: Sucrase Image from: http://awesomebiology. wikispaces
What do these enzymes do? lactase breaks down lactose (sugar found in milk) ATPase Breaks off a phosphate group from ATP, resulting in ADP, an inorganic phosphate, and energy amylase breaks down starch (in saliva & intestine)
What about this one? ATP synthase synthesizes ATP from ADP and inorganic phosphate
Animation Activation Energy & Enzymes: http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html
Factors Affecting Enzyme Activity temperature pH substrate concentration enzyme concentration presence of cofactors or coenzymes Increasing the substrate concentration increases the reaction rate to a certain point. Once the enzymes are saturated with substrate, the concentration of enzyme becomes the limiting factor. Protein (enzyme) folding depends on interactions between amino acid side (R) groups, some that are acidic or basic. Each protein (enzyme) has an optimal pH at which they fold correctly. Temperature – At high temperatures, enzymes become denatured and don’t function. At low temperatures, enzymes are too rigid to catalyse a reaction. Enzymes usually function best at body temperature (37C in humans).
Cofactors and Coenzymes some enzymes require cofactors to function as catalysts cofactors are non-protein molecules or inorganic ions coenzymes are organic cofactors Cofactors: Zn, Fe ions, etc. Coenzymes: NAD, FAD, CoA, etc. 15
Coenzymes (Image from: http://en. wikibooks 16
Enzyme Regulation 17
Competitive Inhibition 18
Competitive Inhibition competitive inhibitors have a similar structure to the substrate bind to the enzyme’s active site and block the substrate from binding. 19
Allosteric Regulation some enzymes have allosteric sites (receptor sites away from the active site) allosteric sites can bind substances that inhibit or stimulate an enzyme’s activity 20
Allosteric Regulation 21
Allosteric Regulation allosteric activators promote the action of the enzyme allosteric inhibitors prevent the action of the enzyme by changing the 3-D structure so that the substrate(s) can no longer bind to the active site (i.e. non-competitive inhibition) 22
Feedback Inhibition (Image from: http://classes. midlandstech can be used to regulate multi-step metabolic pathways the end product of a metabolic pathway acts as an allosteric inhibitor of the first enzyme of the pathway http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter8/animations.html# 23
Commercial Uses of Enzymes (Image from: http://housewares detergents cheese lactose-free dairy proucts corn & wheat syrup sweeteners etc. Starch-processing into glucose through enzyme-catalyzed hydrolysis Cheese manufacturing involves enzymes called proteases (rennet) and lipases Dairy products without lactose. Detergents often contain proteases and amylases to remove protein and carbohydrate stains.