Post on 23-Jun-2015
2.5 Enzymes
KEY CONCEPTEnzymes are catalysts for chemical reactions in living things.
2.5 Enzymes
Chemical Reaction = one or more substances are changed into new substances by the breaking and/or forming of chemical bonds
ex. cracker in the mouth:
polysaccharide monosaccharide
2.5 Enzymes
How do you know if a reaction has occurred?
When one or more of the following has occurred:
1. Formation of precipitate (a new solid compound forms from two solutions)
2. Change in color3. Production of gas4. Change in temperature
Endothermic Rxn – takes in heat (gets cold)Exothermic Rxn – gives off heat
2.5 Enzymes
Reactions are shown as balanced equations Which means, each side has the same elements and the same number of elements on each side
2H2 + O2 2H2O
Reactants Products
Checking for balanced equations...
compare reactants and products:
Reactants
2H2 = 4 Hydrogens
O2 = 2 Oxygens
Products
2 molecules of H2O = 4H and 2O
2.5 Enzymes
• How do you speed up a chemical reaction?
– Temperature– Catalyst
2.5 Enzymes
A catalyst lowers activation energy.
• Catalysts are substances that speed up chemical reactions.– decrease activation energy– increase reaction rate (this is the speed of the rxn)
2.5 Enzymes
Enzymes allow chemical reactions to occur under tightly controlled conditions.
• Enzymes are catalysts for chemical rxns in living things.– Enzymes are needed for almost all processes.
– Most enzymes are proteins.
2.5 Enzymes
• Disruptions in homeostasis can prevent enzymes from functioning. Need stable conditions.
– Enzymes function best in a small range of conditions.– Changes in temperature and pH can break
hydrogen bonds. This affects enzyme function.– An enzyme’s function depends on its structure.– Large changes in temp. and pH change shape
(structure) called denature
2.5 Enzymes
• An enzyme’s structure allows only certain reactants to bind to the enzyme. Shape determines function!
– substrates– active site
substrates (reactants)
enzyme
Substrates bind to anenzyme at certain places
called active sites.
2.5 Enzymes
• The lock-and-key model helps illustrate how enzymes function.
– substrates brought together– bonds in substrates weakened
Substrates bind to anenzyme at certain places called active sites.
The enzyme bringssubstrates together and weakens their bonds.
The catalyzed reaction formsa product that is releasedfrom the enzyme.
2.5 Enzymes
Some Enzymes and their substrates
Enzyme
• Catalase• DNA Polymerase• RNA Polymeras• Maltase• Lactase• Sucrase• Amylase
Substrate
• Hydrogen peroxide• DNA• RNA• Maltose• Lactose• Sucrose• Starch