Enzymes

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 1 Enzymes are biological catalysts made up of proteins used to speed up rate of chemical reactions. They lower activation energy by providing an alternative pathway and remains chemically unchanged at the end of the chemical reaction. Characteristics of enzymes: • three dimensional shape held by weak hydrogen bonds • specific in nature • affected by temperature and pH • can catalyse reversible reactions Human salivary amylase Types of enzymes  Hydrolases are hydrolytic enzymes that use water to cleave chemical bonds, usually dividing a large molecule into two smaller molecules. Examples of common hydrolases include esterases, proteases, glycosidases, nucleosidases, and lipases.  Synthases are enzymes that catal ase the synthesis of a substance without the use of a high-energy source such as cleavage of a phosphate bond in ATP.  Synthetases are enzymes that catalyses the linking together of two molecules especially by using the energy derived from the concurrent splitting off of a pyrophosphate group from a triphosphate (as ATP).

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 2 LO: Explain enzyme action in terms of the ‘lock and key’ hypothesis ● Enzyme is the “lock” ● Substrate is the “key” ● Specific substrate fits into active site of the enzyme. The three dimensional shape of the substrate is complementary to the shape of the active site of the enzyme ● Formation of enzyme-substrate complex ● Reaction takes place then the enzyme and substrate separates. ● Enzymes remain chemically unchanged at the end of the chemical reaction.

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 3 The induced fit model LO: Explain the mode of action of enzymes in terms of an active site, enzyme- substrate complex, lowering of activation energy and enzyme specificity ● Enzyme binds to the substrate at the active site on the enzyme molecule. ● Results in the formation of an enzyme-substrate complex. ● Enzymes reduce the activation energy needed for the reaction to occur, so the reaction occurs more readily. Activation energy is the energy needed to start a chemical reaction. ● Enzyme specificity due to the three dimensional shape of the enzyme held by weak hydrogen bonds. The active site of the enzyme is complementary to the three dimensional shape of the substrate.

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 4 LO: Investigate and explain the effects of temperature and pH on the rate of enzyme catalysed reactions Temperature Low temperature  Kinetic energy of particles is low, enzyme is inactive.  Enzyme substrate complex formation is slow and rate of reaction is low. Increasing temperature to optimum temperature  Kinetic energy of particles increases, increasing the frequency of collision of the substrate and enzyme molecules.  Rate of formation of enzyme substrate complex increases and rate of reaction increases.  Note: Rate of reaction usually doubles for every 10°C increase.

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 5 Optimum temperature  Enzyme is most active.  Rate of formation of enzyme substrate complex is at its maximum and rate of reaction is the highest. Beyond optimum temperature  Weak hydrogen bonds in three dimensional enzyme structure is broken.  Three-dimensional shape of enzyme is lost and shape of active site is altered.  Substrate can no longer bind to active site of enzyme and no enzyme-substrate complexes are formed.  Enzyme is denatured and rate of reaction decreases to zero. pH Below optimum pH  Weak hydrogen bonds in three dimensional enzyme structure is broken.  Three-dimensional shape of enzyme is lost and shape of active site is altered.  Substrate can no longer bind to active site of enzyme and no enzyme-substrate complexes are formed.  Enzyme is denatured and rate of reaction decreases to zero. Optimum pH  Enzyme is most active.  Rate of formation of enzyme substrate complex is at its maximum and rate of reaction is the highest. Above optimum pH  Weak hydrogen bonds in three dimensional enzyme structure is broken.  Three-dimensional shape of enzyme is lost and shape of active site is altered.  Substrate can no longer bind to active site of enzyme and no enzyme-substrate complexes are formed.  Enzyme is denatured and rate of reaction decreases to zero.

Name: __________________ Topic: Enzymes Concepts Summary Notes Nan Hua High School Biology 6 Industrial uses of enzymes