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16th October Enzymes Learning objective: to examine what enzymes are and describe how they work. What are they? Enzymes Why do we need them? Name some examples ? Enzymes Globular proteins that catalyse chemical reactions in living organisms Properties Enzymes Globular proteins that catalyse chemical reactions in living organisms Specific Properties Enzymes Globular proteins that catalyse chemical reactions in living organisms Specific Properties Increase rate of the reaction Enzymes Globular proteins that catalyse chemical reactions in living organisms Specific Properties Increase rate of the reaction Unchanged at the end of the reaction Enzymes Globular proteins that catalyse chemical reactions in living organisms Specific Properties Increase rate of the reaction Unchanged at the end of the reaction Need them Enzymes Globular proteins that catalyse chemical reactions in living organisms Specific Properties Increase rate of the reaction Unchanged at the end of the reaction Reactions too slow to maintain life Need them Can’t increase temperatures/pressure in cells (fatal) Enzymes Are Proteins The enzyme binds to the substrates by its active site The active site is a pocket formed by the folding of the protein where the substrates bind. Enzymes Are Proteins The enzyme binds to the substrates by its active site The active site is a pocket formed by the folding of the protein where the substrates bind. Active site The active site involves a small number of key residues that actually bind the substrates The rest of the protein structure is needed to maintain these residues in position How do enzymes work? An Example An Example Sucrose + H2O Glucose + Fructose An Example Substrates Sucrose + H2O Glucose + Fructose Products For a reaction to occur the sucrose and water would have to collide with enough energy to break and form bonds For a reaction to occur the sucrose and water would have to collide with enough energy to break and form bonds This is the activation energy Sucrose + H2O + Substrates Glucose + Fructose + Products Energy Progress of reaction Energy Substrates Progress of reaction Energy Substrates Progress of reaction Products High energy intermediate Energy Substrates Progress of reaction Products High energy intermediate Activation energy Energy Substrates Progress of reaction Products The minimum amount of energy needed to start the reaction, leading to the formation of a high energy intermediate = The Activation energy High energy intermediate Activation energy Enzymes reduce the height of the energy barrier Energy Substrates Progress of reaction Products Questions Read page 57-60 1. Write a definition for the following: Active Site Substrate Products 2. Explain how the structure of the protein is linked to its ability to act as an enzyme? 3. How does heating a mixture increase the chance that a chemical reaction Will occur? Why can’t this approach be used in cells? 4. Write a paragraph in your own words describing how enzymes act as catalysts by lowering activation energy. This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.
