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Testing for Protein. Open to your completed lab. Any questions?. 1. Enzymes. Enzymes. biological catalysts proteins that speed up chemical reactions without being consumed. Modeling Enzymes. 6. Enzyme Action. enzymes bind to specific reactants called substrates
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Testing for Protein • Open to your completed lab. • Any questions? 1
Enzymes • biological catalysts • proteins that speed up chemical reactions without being consumed
Enzyme Action • enzymes bind to specific reactants called substrates • substrates bind to active sites on enzymes, forming the enzyme-substrate complex
Induced-Fit Model • in the “induced-fit” model, the enzyme alters its shape to better “fit” substrate • contrast with the “lock and key” hypothesis
What reactions do these enzymes catalyze? lactase • breaks down lactose (sugar found in milk) amylase • breaks down starch (in saliva & intestine) Alcohol Dehydrogenase • breaks down alcohol (in the stomach and liver)
Cofactors and Coenzymes • Some enzymes require: • cofactors (non-protein molecules or inorganic ions - often metals); • they bind to the enzyme and allow it to function • coenzymes (organic cofactors eg., some vitamins or minerals) • they may shuttle molecules from one enzyme to another
Factors AffectingRate of Enzyme Activity • temperature • What is the affect of temperature on the activity of amylase? • How will you know if amylase works? • What different treatments will you use? • What is your + control? - control?
How will you know that it is amylase that is digesting the starch (Does starch break down on its own? Does starch break down on its own at different temperatures?) 18
pH • substrate concentration • enzyme concentration 19
T/P/S • Pepsin is an enzyme produced in the stomach that breaks down protein. Knowing that enzymes work at particular pHs, Curtis set up an experiment to see what pH at which pepsin works best. 20
After time… • Curtis set up the following: • egg cube + egg cube+ egg cube + • pepsin + pepsin + pepsin + • pH2 pH 7 pH 10 • (HCl) (water) (NaOH) • a) Hypothesize at which pH pepsin will work best. • b) What conclusions can you make? 21
Curtis set up the following: • egg cube + egg cube+ egg cube + • pepsin + pepsin + pepsin + • pH2 pH 7 pH 10 • (HCl) (water) (NaOH) • a) Hypothesize at which pH pepsin will work best. • b) What conclusions can you make? 22
Enzyme Inhibitors Competitive Inhibitors • have a similar structure to the substrate • bind to the enzyme’s active site and block the substrate from binding
Irreversible Inhibitors Many drugs & pesticides act as irreversible inhibitors of enzymes • cyanide (inhibits key enzymes in cellular respiration) • antibiotics (inhibit bacterial enzymes)
Irreversible Inhibitors Similar to Competitive inhibitors • exception to destroying the enzyme activity altogether by never letting go or destroying the active site. Many drugs & pesticides act as irreversible inhibitors of enzymes •Sarin gas used in Syria •antibiotics (inhibit bacterial enzymes)
Allosteric Regulation • some enzymes have allosteric sites • allosteric regulators either inhibit or stimulate an enzyme’s activity
Allosteric Regulation • allosteric activators promote the action of the enzyme • allosteric inhibitors prevent the action of the enzyme (i.e. noncompetitive inhibition)
Feedback Inhibition • often used to regulate multi-step metabolic pathways • the product of a pathway usually acts as an allosteric inhibitor of the first enzyme of the pathway • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter8/animations.html#
Homework • Read Page 52 “Enzyme & Substrate Concentration” • - make summary notes • Read Page 55 “pH & Temperature Effects” • - make summary notes 33
Modelling Enzymes • Groups of 3 • Put 50 pennies tails up • In 10 seconds, one person turns as many pennies over as possible • Consider how you could model: • denaturation of an enzyme • co-enzymes • competitive inhibitors • negative feedback • allosteric inhibitors/ activators 35
Commercial Uses of Enzymes • Enzymes are used throughout industry: • Detergents • Textiles • Foods & Beverages • Leather • Biodegradable Plastics • Bioethanol • Paper & Pulp • Wastewater treatment
Enzymes in Industry • Get with your group & compare your enzymes. (5 minutes) • Detergents • Textiles • Foods & Beverages • Leather • Biodegradable Plastics • Bioethanol • Paper & Pulp • Wastewater treatment • “Walkabout” & complete your table for at least 3 enzymes. 40
Summarizing • The internal structures of a cell interact and complement each other in both forms and function. In eukaryotic cells, internal structures, or organelles, carry out specialized functions. Some organelles isolate toxic or harmful substances from the rest of the cell or provide a favourable environment for a reaction that could not occur in the cytosol. Other organelles transport substances through the cytosol, maintaining the fluid balance. The shapes of some organelles are quite elaborate, because each organelle is adapted to perform specific functions. 41
Summarizing • The cell itself, and many organelles within it, are bounded by membranes that control the amounts and types of substances that move in and out of the cell or organelle. The plasma membrane forms a barrier around the cytosol of the cell. The membrane surrounding an organelle maintains an internal environment that allows the organelle to carry out its particular function. 42
Summarizing • An organelle rarely works alone. Just as your organ systems work together to keep your body functioning, it takes a team of organelles to keep a cell running. Substances move between different organelles and the plasma membrane. Some metabolic pathways take place in a series of different organelles. At the same time, the cell needs to reproduce itself to generate more cells. 43
Complete your organelle summary page. • Structure • Function • Analogy (factory) • Diagram 44
Organelle Exchange • Pick up a chart. • Sit with your original organelle group with a writing utensil or two. 45
Homework (ahhh….) • Page 80 # 1, 4, 5, 7, 8 50
