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INVESTIGATING ENZYMES How An Enzyme Works Enzymes in living cells PROTEINSALL LIVING CELLS.  Enzymes are PROTEINS which are present in ALL LIVING CELLS.

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Presentation on theme: "INVESTIGATING ENZYMES How An Enzyme Works Enzymes in living cells PROTEINSALL LIVING CELLS.  Enzymes are PROTEINS which are present in ALL LIVING CELLS."— Presentation transcript:



3 How An Enzyme Works

4 Enzymes in living cells PROTEINSALL LIVING CELLS.  Enzymes are PROTEINS which are present in ALL LIVING CELLS. SPEEDING UP  They act as biological CATALYSTS by SPEEDING UP chemical reactions without being used up itself.  Why do we need enzymes ? most cells work at relatively low temperatures and their chemical reactions (e.g. respiration, digestion, photosynthesis) would be too slow to sustain life without the help of enzymes !

5 Uses of enzymes 1) Enzymes are used in washing powders to help digest food stains. Biological washing powders will only work on 40 0 C or lower. 2) Enzymes are used in baby foods to “pre-digest” the proteins. 3) Enzymes are used to convert starch into sugar which can then be used in food.

6 Enzyme Specificity is called the lock- key hypothesis!!

7 ENZYME DESIGN  The substance on which an enzyme acts is called the SUBSTRATE  The reaction happens when the ENZYME molecule and the SUBSTRATE molecule are fitted together  Each ENZYME has to be shaped EXACTLY to suit its own substrate

8 Examples – Notice the “ase” ending SUBSTRATEENZYME UreaUrease LipidLipase LactoseLactase Lactase only works with Lactose etc.

9 ACTIVATION ENERGY- the energy needed to start a chemical reaction Enzymes lower the amount of activation energy needed!!

10 reactants products energy barrier with no enzyme to promote reaction energy barrier with an enzyme’s participation Activation Energy

11 Enzymes – How they work! Enzymes Protein Polymer Lots of Smaller Amino-acids (monomers)

12 The concept of metabolism  Metabolism = all the chemical reactions taken place inside the living organisms  Metabolic reactions produce different life processes, e.g. –photosynthesis –respiration –movement –growth –reproduction

13 Control of metabolism  Metabolic reactions can be controlled and speeded up by enzymes –metabolic reactions would be too slow to occur if no enzymes are present!

14 Catabolic/decomposition chemical reactions..  Involve the BREAKDOWN of big molecules into smaller ones (Hydrolysis)

15 Anabolic/synthesis chemical reactions..  BUILD UP smaller molecules into bigger ones (Dehydration Synthesis) Without enzymes, chemical reactions in living cells would be far too slow!!

16 Temperature & Enzyme Activity PROTEINDENATURED All enzymes are made of PROTEIN so are DENATURED at high temperatures (above about 50°C).. think boiled eggs !! OPTIMUM TEMP The rate of enzyme activity increases with temperature up to a maximum (OPTIMUM TEMP.) then falls to zero as the enzyme is denatured.

17 pH & Enzyme Activity  pH range of pH  pH also affects the rate of enzyme activity. Each enzyme has its own range of pH in which it will work.  Examples : PEPSIN the enzyme PEPSIN only works between (pH 1-4)pH 1 - pH 4 (acidic) CATALASE the enzyme CATALASE only works between (pH 8-11)pH (alkaline)  Optimum very fastest  Optimum = "the best”... The enzyme is working at its very fastest

18 More reaction facts…  An example of a BREAKDOWN reaction.  The enzyme,AMYLASE breaks down STARCH into MALTOSE  An example of a SYNTHESIS reaction...  The enzyme PHOSPHORYLASE builds up glucose(-1 phosphate) into STARCH. BUT REMEMBER,EACH ENZYME CAN ONLY CATALYSE ONE REACTION.

19 DENATURATION  Enzymes are made of proteins  Proteins are sensitive to external conditions such a temperature, pH, salt levels etc  If conditions change it can cause the active site of an enzyme to change shape  When this happens, the substrate can no longer fit and the enzyme quits working

20 And finally...  ‘Optimum’ is a useful word which means ‘best’  So we call the TEMPERATURE and the pH which makes an ENZYME work at its very fastest, the OPTIMUM for that enzyme.

21 One More Time ……

22 Use the drawing to answer the question


24 Enzymes in the Digestive System

25 Cracker Lab – Exploring Amylase “Enzyme Madness”

26 Apple Experiment  Observe the two apple bites. What is different about them? Why?  An enzyme present in apples is called catecholase. When catechol and oxygen interact, the enzymatic reaction causes the apple to brown. The low pH of the lemon, however, stops this reaction.

27 “An Apple a Day ……”  Take a bite of an apple. On the opposite side of the apple take a second bite. Rub lemon juice on the second bite mark and set your apple aside.

28 Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. Enzymes are denatured beyond 40 O C Enzymes work best in certain conditions: Enzyme activity TemppH 40 0 C Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzymes vary in the pH and temperatures that make them work best!

29 In Your Journal write:  Name industries that use enzymes to improve their products.  How did the Egyptians use enzymes?  Where was Rennin collected from in the past?  Discuss how large quantities of enzymes are currently produced.  Could we survive without enzymes? The Following Video will provide the answers


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