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Enzymes’

Enzyme Characteristic 1 Enzymes _________ __________ chemical reactions. speedup

Enzyme Characteristic 2 Tube ATube BTube C Tube ATube BTube C ContainsH 2 O 2 & sandH 2 O 2 & liver Observation

Tube ATube BTube C Minute amounts of enzymes is needed to speed up the rate of reaction, without being chemically changed at the end of the reaction. Enzymes are required in minute amounts.

Maltase Enzymes are required in minute amounts. At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions. Maltose Glu

Maltase At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions. Maltose Glu Enzymes are required in minute amounts.

Maltase At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions. Maltose Glu Enzymes are required in minute amounts.

Maltase At the end of a chemical reaction, enzymes remain chemically unchanged and capable of catalysing more reactions. Maltose Glu Enzymes are required in minute amounts.

Maltase Maltose Glu Hence, a minute amount of enzymes is enough to catalyse a chemical reaction. Enzymes are required in minute amounts. Since enzymes remain chemically unchanged in the reactions they catalyse, the same enzyme can be used over and over again.

Recall How do we name enzymes? Based on the substrate they act on!

Enzymes are substrate specific. Amylase Starch Protease Proteins Enzyme Characteristic 3 ACT ON Lipids/ FatsLipase Substrates ACT ON

Enzyme Characteristic 3 An Enzyme

Active site A depression on the surface of an enzyme molecule into which the substrate molecule(s) can fit Enzyme Characteristic 3 The specificity of an enzyme is due to its surface configuration or active site.

Demonstration

According to the “lock and key” hypothesis, the enzyme action depends on the active site.

Unsuitable substrate molecules will NOT FIT into the active site. Hence, the enzyme will not catalyse the reaction. A B

C D CD ONLY suitable substrate molecules will fit into the active site. The enzyme will then be able to catalyse the reaction.

Only certain substrate can fit the active site of an enzyme.

lock key

lock key The formation of enzyme-substrate complex will lower the activation energy and brings about the necessary reactions converting the substrate molecules into product molecules.

The energy that must be overcome in order for a chemical reaction to occur. Energy Time Activation energy for a reaction without a catalyst (enzyme) What is Activation Energy? reactants products

The energy that must be overcome in order for a chemical reaction to occur. Energy Time Activation energy for a reaction with a catalyst (enzyme) What is Activation Energy? reactants products

Each enzyme is a molecule with a specific shape. On part of its surface is the active site (the lock)—a section where its substrate molecule (the key) fits exactly.

When the substrate molecule is in position in the active site, the enzyme alters the substrate, splitting it into its product molecules.

The product molecules drift away from the enzyme molecule leaving its active site free to operate again.

Hmm… enzymes seemed to be so powerful… Is there anything that can affect it?

What happens to the movement of the enzymes and substrates as temperature increases? Why do you think the rate of enzymatic reaction increases as temperature increases? Ans: The movement of the enzymes and substrates increases, resulting in higher collision rates. Ans: The increase in collision rates results in an increase in the formation of enzyme-substrate complex, thereby resulting in an increase in the rate of enzymatic reaction.

Which temperature do you think is the optimum temperature? What happens to the enzyme when the temperature exceeds that particular temperature? What do you think is the meaning of optimum temperature? What does ‘denatured’ mean? Ans: 40 °C. The enzymes are denatured. The optimum temperature is the temperature at which the enzyme is most active, catalysing the largest number of reactions per second. Ans: Its structure had been irreversibly changed.

Temperature Rate of reaction (enzyme activity) 0 1 Enzyme is less active at very low temperatures 2 As the temperature rises, rate of reaction increases due to increase in enzyme activity. The enzyme is twice as active for every 10°C rise in temperature until the optimum temperature is reached 3 Enzyme is most active at its optimum temperature 4 Beyond optimum temperature, enzyme activity decreases 5 Zero enzyme activity  lost its ability to catalyse the reaction

What happens to the enzymes as the pH increases above 7? Which pH do you think is the optimum pH? Ans: pH 7. Ans: The enzymes began to denature. What happens to the enzymes as the pH decreases above 7? Ans: The enzymes began to denature. At what pH levels are the enzymes completely denatured? Ans: pH 4 and pH 9.

 Optimum pH usually at pH 7 but different enzymes have varying optimum pH  Some work best in slightly acidic solutions: - rennin and pepsin (stomach)  Some work best in slightly alkaline solutions – intestinal enzymes

Denaturation Denatured protein! Active site is lost! Active site It is the change in the three-dimensional structure of an enzyme or any other soluble protein, caused by heat or chemicals such as acids or alkalis.

What we learn today. Characteristics of Enzymes (Think: What are they?) What is Activation Energy? “Lock and Key” Hypothesis (Describe) Temperature and Enzymes (How does temperature influence the enzymes?) pH and Enzymes (How does pH influence the enzymes?)