3Enzymes in living cells Enzymes are PROTEINS which are present in ALL LIVING CELLS.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 !
4Uses of enzymesDaz1) Enzymes are used in washing powders to help digest food stains. Biological washing powders will only work on 400C 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.
5Enzyme Specificity is called the lock- key hypothesis!!
6ENZYME DESIGNThe substance on which an enzyme acts is called the SUBSTRATEThe reaction happens when the ENZYME molecule and the SUBSTRATE molecule are fitted togetherEach ENZYME has to be shaped EXACTLY to suit its own substrateEggs are made of protein. When an egg is fried its protein denatures. It takes on a different shape and cannot be returned to its precooked state.
7Examples – Notice the “ase” ending SUBSTRATEENZYMEUreaUreaseLipidLipaseLactoseLactaseLactase only works with Lactose etc.
8ACTIVATION ENERGY- the energy needed to start a chemical reaction Enzymes lower the amount of activation energy needed!!
9Activation Energy reactants energy barrier with no enzyme to energy promotereactionenergybarrier withan enzyme’sparticipationproducts
10Enzymes – How they work! Enzymes Protein Polymer Introduce yellow and red sequence as a piece of protein made up of amino- acid building blocks.Lots of Smaller Amino-acids (monomers)
11The concept of metabolism Metabolism = all the chemical reactions taken place inside the living organismsMetabolic reactions produce different life processes, e.g.photosynthesisrespirationmovementgrowthreproduction
12Control of metabolismMetabolic reactions can be controlled and speeded up by enzymesmetabolic reactions would be too slow to occur if no enzymes are present!
13Catabolic/decomposition chemical reactions.. Involve the BREAKDOWN of big molecules into smaller ones (Hydrolysis)
14Anabolic/synthesis chemical reactions.. BUILD UP smaller molecules into bigger ones (Dehydration Synthesis)Without enzymes, chemical reactionsin living cells would be far too slow!!
15Temperature & Enzyme Activity All enzymes are made of PROTEIN so are DENATURED at high temperatures (above about 50°C) .. think boiled eggs !!The rate of enzyme activity increases with temperature up to a maximum (OPTIMUM TEMP.) then falls to zero as the enzyme is denatured.
16pH & Enzyme ActivitypH also affects the rate of enzyme activity. Each enzyme has its own range of pH in which it will work.Examples :the enzyme PEPSIN only works between (pH 1-4)pH pH 4 (acidic)the enzyme CATALASE only works between (pH 8-11)pH (alkaline)Optimum = "the best” ... The enzyme is working at its very fastest
17More reaction facts… An example of a BREAKDOWN reaction. The enzyme,AMYLASE breaks down STARCH into MALTOSEAn example of a SYNTHESIS reaction...The enzyme PHOSPHORYLASE builds up glucose(-1 phosphate) into STARCH.BUT REMEMBER,EACH ENZYME CAN ONLYCATALYSE ONE REACTION.
18DENATURATION Enzymes are made of proteins Proteins are sensitive to external conditions such a temperature, pH, salt levels etcIf conditions change it can cause the active site of an enzyme to change shapeWhen this happens, the substrate can no longer fit and the enzyme quits working
19And 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.
25Apple ExperimentObserve 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.
26“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.
27Enzymes work best in certain conditions: Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction.Enzymes work best in certain conditions:Could be protease (found in the stomach)Enzymes are denatured beyond 40OCCould be amylase (found in the intestine)Enzyme activityTemppH400CEnzymes vary in the pH and temperatures that make them work best!
28The Following Video will provide the answers 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?