Grade 10 - Enzymes Enzyme Action

Changing Reaction Rates Certain factors help speed up reactions which normally would take a long time to proceed. An example of this is when Hydrogen Peroxide breaks down to form water and oxygen: 2H2O2 2H2O + O2 When this reaction is heated, the reaction rate (amount of chemical change per unit time) increases! The energy (e.g. Heat) required to make any chemical reaction proceed is called the ACTIVATION ENERGY (Hydrogen Peroxide) (Water) (Oxygen)

Catalysts Not only does heat (temperature) effect the reaction rate, but other chemicals also help speed the reactions up. Manganese Dioxide is a chemical which helps the Hydrogen Peroxide reaction proceed faster. A substance which increases the rate of reaction is called a CATALYST. There are also biological (protein) catalysts and these are called ENZYMES! Enzymes are protein molecules which occur naturally in all living cells. Catalase is an enzyme found in liver cells which helps speed up the Hydrogen Peroxide reaction.

Properties of an Enzyme: Biological Catalyst Lowers the energy input/activation energy required for a chemical reaction to proceed. Speeds up rate of reaction Enzymes are proteins Enzymes remain unchanged after a reaction and therefore can work again. Enzymes are specific to a substrate of a reaction (Lock and Key). Enzymes are reversible and can catalyse a reaction going both ways (Synthesis/Lysis) Enzymes are denatured by: Change in Temperature Change in pH Therefore have an optimum Temperature and pH, where it works most effectively. In Humans that is usually around 37˚C and a pH of 7.

Catalase experiments

Activation energy with/without Enzymes (Substrates) (Products)

ENZYME-SUBSTRATE COMPLEX Specificty of Enzymes Lock and Key Mechanism: On Enzyme surface there is the active site which fits specifically with the substrate molecule it is suited to work on. Active Site Active Site unchanged, can now work on a new substrate. SUBSTRATE ENZYME-SUBSTRATE COMPLEX PRODUCTS

Degradation of Complex Substrate Degradation/lysis (breaking down) of complex substrate

Synthesis of Complex Product Synthesis (building up) of complex product

Effect of Amylase Enzyme on starch (Degradation) glucose glucose glucose glucose glucose glucose Amylase Enzyme glucose glucose glucose glucose MALTOSE glucose Amylase Enzyme glucose glucose glucose glucose glucose Amylase Enzyme glucose glucose glucose glucose

Effect of phosphoraylase on Glucose-1-phosphorylase (Synthesis) Glucose-1-Phosphate How do you test for starch? (Iodine)… so wouldn’t this be a good test to see the effect of Phosphorylase Phosphorylase Enzyme Bond forming between two Glc molecules Glucose-1-Phosphate Phosphorylase Enzyme Ect…………. STARCH molecule formed Phosphorylase Enzyme

The equations for the previous reactions: Effect of amylase (degradation) Starch Maltose (simple sugar) Effect of potato phosphorylase (synthesis) Glucose-1-phosphate Starch (Substrate) (Products) Amylase (Substrate) (Products) Potato Phosphorylase

Effect of Temp/pH on Enzyme Activity Optimum Temp/pH for enzyme activity! Rate of Reaction/Enzyme Activity Enzyme is becoming denatured (the active site is being physically altered (permanent damage) Temp/pH (Arbitary units)

Digestion of starch by amylase

pH and Enzyme activity