Enzyme and Metabolism PDF

Enzyme and metabolism Metabolism different chemical reactions are taking place in an organism sum of the chemical reactions that take place in an organism = metabolism ( 新陳代謝 )  Metabolism Catabolism Anabolism ( 分解代謝 ) ( 合成代謝 )  Catabolism complex e...

Enzyme and metabolism Metabolism different chemical reactions are taking place in an organism sum of the chemical reactions that take place in an organism = metabolism ( 新陳代謝 )  Metabolism Catabolism Anabolism ( 分解代謝 ) ( 合成代謝 )  Catabolism complex energy simple molecul molecule e s breaking-down reactions release of energy  Catabolism example: respiration carbon water + dioxide glucose energy  Metabolism Catabolism Anabolism  Anabolism simple complex energy molecule molecul s e building-up reactions requires energy  Anabolism example: condensation of glucose starch glucose energy Common usage of the terms Catabolism and anabolism can be (or usually) refering to a chain reaction, or a series of reaction. Metabolic rate overall speed of the chemical reactions in the organisms Affected by many factors! Chemical energy needs energy to occur! Chemical energy needs energy to occur!  energy reacting product molecules Energyenergy supplied to overcome the barrier ( 能障 energy barrier )  analogy: pushing a rock up a hill reacting molecul e energy produc barrier t ­ the reaction does not start due to the presence of energy barrier  analogy: pushing a rock up a hill maximum energy energy ­ energy is supplied …reaction starts when By increasing the temperature? smaller energy barrier energy level raised energy barrier is easier to overcome By increasing the temperature? Not possible smaller because high energy temperature barrier kill the body cells! energy level raised energy barrier is easier to overcome  lower energy barrier rate of chemical reactions is speeded up by enzymes  energy Enzymes are proteins which act as biological catalyst Enzymes speed up chemical reactions by lowering the energy barrier. Formation of enzyme-substrate complex could help providing an alternative reaction pathway with a lower activation energy to allow the chemical reaction to occur in living cells and speed up the reaction rate. Metabolic reactions would proceed very very slowly or even stop without enzymes. In our body, without enzyme energy activation energy level reactants enzymes function as biological catalysts products  activation energy progress of reaction In our body, without enzyme with enzyme energy lowered level activation energy reactants reaction rate products progress of reaction  each enzyme has an active site of a specific shape active site enzym e  active site can combine with substrate molecule(s) substrat shapes fit e together! enzym e  substrat enzyme- e substrate enzym complex e Formation of enzyme-substrate complex could help providing an alternative reaction pathway with a lower activation energy to allow the chemical reaction to occur in living cells and speed up the reaction rate.  active site can combine with substrate molecule(s) substrat enzyme- e substrate enzym complex e complex breaks down to give product(s)  In catabolic reactions, the enzyme helps to break the substrates apart.  In anabolic reactions, the enzyme helps to join the substrates together.  The enzyme substrate complex then breaks down to give the product. The enzyme is released in its original form. Enzymes are acting as biological catalysts 19-DSE-Q2 15-DSE-Q7 15-DSE-Q7 Properties of enzyme Lock and key hypothesis  The lock-and-key hypothesis explains the specificity of enzyme action. Enzymes combine with a particular substrate only, like a key only fits in a an enzyme particular lockwith a specific active site binds only to a particular substrate  The lock-and-key hypothesis explains the specificity of enzyme action. Enzymes combine with a particular substrate only, like a key only fits in a an enzyme particular lockwith a specific active site binds only to a particular substrate  An active site can only fit specific substrate(s) to form enzyme- substrate complex, so enzyme is specific in action  After finishing the reaction, the enzyme will be released again with an intact active site, so enzyme is reusable. reused reused  1) Enzyme is Reusable enzyme returns to its original form after reaction before after reactio reactio n same! n 1) Enzyme is required in small amount large amount of products produced reusable reusable reusable 2) They are specific in action different shape!  2) Specific action each enzyme combines with a specific substrate  each enzyme catalyses only one type of reaction  2) Specific action can be explained by lock-and-key hypothesis ( 鎖鑰假說 )  3) Biological catalysts act as catalysts in organisms speed up metabolic reactions  4) Enzymes are Proteins enzymes are denatured at high temperatures and extreme pH 5) Enzymes work best in different conditions Enzymes work best under optimum temperature and pH value. Factors affecting rate of enzymatic reactions  How to measure enzymatic rate? carbo water + n glucose dioxid energy e Measure the rate of Measure the substrates being rate of product used up formation 1. Temperature reaction rate At low temperatures temperature (°C) 10 20 30 40 50 60 50  1. Temperature Simulation 4. 1 At low temperatures: low kinetic energy of enzyme and substrate molecules  enzyme inactive move slowly  less chance to collide reaction rate 51 1. Temperature reaction rate At low temperatures As temperature rises temperature (°C) 10 20 30 40 50 60 52  1. Temperature As temperature rises: more kinetic energy move more rapidly  collide more frequently enzyme activity enzyme-substrate complex 53 1. Temperature reaction rate maximum enzyme activity optimum temperature temperature (°C) 10 20 30 40 50 60 54 1. Temperature reaction rate At high temperatures temperature (°C) 10 20 30 40 50 60 55  1. Temperature When temperature becomes too high: conformational change of active site  enzyme denatured substrates no longer fit loses catalytic the active site enzyme-substrate complex enzyme activity ability permanently56 08-CE-BIO Q6 (a) Ginger juice contains an active ingredient/ heat sensitive substance/ enzyme that causes the curding of milk 1M (b) The active substance/ heat-sensitive substance/ enzyme is protein in nature 1M Which is denatured by high temperature 1M Therefore, if the protein is involved, the action will be lost after boiling 1M OR The active ingredient/ heat sensitive substance is a volatile substance 1M Which is evaporated by high temperature 1M Therefore, if a volatile substance is involved, the action will be lost after boiling 1M (c) Follow the steps in the recipe for one set-up 1M And heat the milk to 65oC instead of steps 2 and 3 in another setup 1M OR Boil the milk, cool down to 65oC and mix with ginger juice Heat the milk to 65oC and mix with ginger juice 10-CE-BIO Q1 (i) 25 1M (ii) To make the results of the two set-ups comparable/ to eliminate the effect of temperature on the results 1M (a) The gelatin layer of the photographic film is removed by the unboiled washing powder solution. 1M This shows that the washing powder contains protein-digesting substance. 1M However, the ability to remove the gelatin is lost when the washing powder solution is boiled. 1M This shows that the protein-digesting substance in the washing powder is heat sensitive. 1M This substance is probably protease. (b)Egg stains contain proteins 1M Protease digests the insoluble protein into peptides which are soluble, so it can be removed by water easily. 1M  2. pH at optimum pH enzyme activity is reaction maximum rate pH 2 4 6 8 10 12 14 61  many enzymes in mammals 2. pH (e.g. salivary amylase): pH 7 pepsin: pH 2 pancreatic lipase: pH 9 reaction rate different enzymes have different optimum pH pH 2 4 6 8 10 12 14 62  2. pH optimum pH At low pH At high pH reaction rate pH 2 4 6 8 10 12 14 63  2. pH An unsuitable pH: conformational change of active site  enzyme denatured substrates no longer fit the active site enzyme-substrate complex enzyme loses its catalytic ability permanently 64 03-CE-BIO Q3b (i) The catalase in the paper disc broke down hydrogen peroxide, releasing oxygen 1M When the amount of oxygen evolved reached a certain level, the oxygen bubbles buoyed up the disc to the surface of hydrogen peroxide solution 1M pH Rate of reaction (s- (ii) 1 ) 3 more active sites for the substates to collide and form enzyme-substrate complex. 4. Substrate concentration PREMISE: With sufficient enzymes Higher substrate concentration higher chance to form enzyme-substrate complex once the enzyme is not occupied 4. Substrate concentration PREMISE: With sufficient enzymes The reaction rate levels off after the saturation point, where all active sites of the enzyme molecules are occupied by substrates. extra Inhibitors substances that decrease the activity of enzymes e.g. cyanides and some heavy metals inhibitor of an enzyme involved in respiration 71 Competitive inhibitors Having a similar shape to the real substrate, the competitive inhibitors can bind with the active sites of the enzymes reversibly. The inhibitory effect can be overcome by increasing the substrate concentration. Non-competitive inhibitors Bind to the allosteric sites of enzyme (Sites other than active sites), and denature the enzymes by changing the shape of the active site of the enzymes. (Either irreversibly or reversibly) The substrate cannot bind to the active sites. The effect of inhibition cannot be overcome by increasing substrate concentration. What are the applications of enzymes? plants, animals or microorganisms extracted from enzymes Food used Biofue processi in ls ng Clothin Medic Person g al al care Food processing e.g. Fruit juice extraction Pectinases catalyse the breakdown of cell walls within fruits release juice inside maximize the yield of fruit juice extraction Food processing e.g. Fruit juice extraction Pectinases catalyse the breakdown of cell walls within fruits clarify the juice (make it clear) Food processing e.g. Baby food digestive systems of babies not yet fully developed proteases pre-digest some of the proteins in food more easily digested and absorbed by babies Food processing e.g. Syrups Amylase catalyses the breakdown of corn starch into sugars Food processing e.g. Meat tenderizers Proteases digest proteins in meat soften meat before cooking Papain! Clothing industry e.g. Stonewashed jeans Traditional method: wash jeans with stones break jeans blue becom dye cellulose e less partiall fibres of stiff overall y production jeans Use of enzymes 👍 cost🡫 remove d Medical e.g. Glucose test strips enzyme in test catalysesend oxidation of glucose changes colour at different concentration of glucose present helps detect the sign of diabetes Medical e.g. Enzyme containing injection for dissolving blood clots Normal blood clotting: seal cuts and stop Patients effectiv bleedingwith excessive e blood clotting: treatme block blood flow nt 🡪 lead to heart attack / stroke Medical e.g. Lysozyme Lysozyme is a common anti-inflammatory drug that naturally exists in various body fluids, Personal care e.g. Contact lens cleaners Proteases remove protein deposits from contact lenses causing discomfort blurring vision proteins deposit on increasing risks the surface of contact lenses of eye Personal care e.g. Biological washing powder ✔ lipases 🡪 act on lipids ✔ amylases 🡪 act on starch ✔ proteases 🡪 act on proteins speed up breakdown of substances in food stains on clothes Biofuels e.g. Fuels produced from plant materials (e.g. Suitable sugar cane or maize) speedenzymes up breakdown of starch in crops into sugars fermentati on produce ethanol as fuel for vehicles Extra applications: refer to your textbook 4-20 and 21 Advantages of using enzymes 1. speed up chemical reactions ⮚ mass-produced more quickly ⮚ higher yield of product Advantages of using enzymes 2. specific in action ⮚ only catalyse specific processes ⮚ give specific products ⮚ less likely to generate undesirable products Advantages of using enzymes 3. reusable ⮚ small amount is needed ⮚ able to convert a lot of substrates into useful products Advantages of using enzymes 4. allow reactions to occur in mild conditions without High enzyme high temperature activati Energy on / pH level energy Progress of reaction Advantages of using enzymes 4. allow reactions to occur in mild conditions with enzyme moderate Energy Low level activati on temperature / pH energy ⮚ reduce Progress of reaction production cost Advantages of using enzymes 5. enzyme activity can be easily regulated by adjusting: ⮚ reaction temperature ⮚ pH Advantages of using enzymes 6. non-toxic and ⮚biodegradable replace certain harmful chemicals of industrial processes ⮚ produce fewer pollutants  Practical 5.5 Vid eo Investigation of enzyme activities in fruits Pineapple juice can be used as a meat tenderizer as it contains proteases. In this practical, you will study the protease activities in different fruit extracts (e.g. pineapple, papaya and kiwi fruit) using milk agar plates.  Practical 5.5 Vid eo Investigation of enzyme activities in fruits A milk agar plate contains milk proteins and is white in colour. If the milk proteins are broken down, a clear zone will form. The higher the enzyme activity, the larger the clear zone will be.  Practical 5.5 Vid eo Procedu re 1. Extract juices from pineapple, papaya and kiwi fruit. Transfer them into three test tubes labelled A to C. Why is cold distilled water added when grinding the fruit pieces? The grinding action produces heat. Adding cold distilled water can prevent the enzymes in the fruits from being denatured by heat.  Practical 5.5 Vid eo 2. Make four wells on a milk agar plate by gently pressing a sterilized cork borer into the plate. Label the wells as A to D. The cork borer is a sharp object. Handle it with care. Practical 5.5 Vid eo cork borer D A milk C B agar wel l  Practical 5.5 Vid eo 3. Transfer three drops of the fruit juice from test tubes A, B and C to the corresponding wells as shown in the table below. Add three drops of distilled water to well D. Cover the milk agar plate immediately with the lid.  Practical 5.5 Vid eo Wel Content l A Pineapple juice fruit B Papaya juice juice C Kiwi fruit juice D A C B D Distilled water wel l Practical 5.5 Vid eo Why is it necessary to include a well of distilled water? The well with distilled water is the control of this experiment. This is to show that the formation of clear zone in the experimental set-ups is due to the fruit juices.  Practical 5.5 Vid eo 4. Incubate the milk agar plate at 35 °C for one hour. 5. Examine the agar plate against a piece of black cardboard. Measure and compare the diameter of any clear zones around the wells.  Practical 5.5 Vid eo Results Diameter of the We Contents clear zone formed ll (mm) Pineapple (Results vary A juice with Papaya students.) B juice Kiwi fruit No clear zone is C observed. juice  Practical 5.5 Vid eo Discussi Clear zones of different diameters are on observed around the wells containing fruit extracts. This shows that pineapple, papaya and kiwi fruit contain proteases that catalyse the breakdown of protein but the activities are different. The well containing distilled water serves as a control. No clear zone