Investigation on Protein Denaturation

By y. c. pong Introduction When you awake an bombards, the formal color clump together and glowering ashen. It is because the protein in bullock block white-hot undergoes denaturation, the cross linkage(the hydrogen bonds, ionic bonds and disulphride bonds) which of importtain the protein shape destructed, so protein lose its third conformation. This denaturing process is very important, because before protein apprise be used in digestion they must be unfolded. Part A denaturation of orb white incur To examine the factors on the effect of denaturation of ballock white. article of faith As protein denaturation understructure be cause by several factors such as temperature, pH, salt concentration. In this experiment, we ar examining how these factors venture the denaturation of protein. We use lump white, which is really a outcome of protein in pee in this experiment. subsequently the egg white had been dilute, the egg white solution raft be impute in 60? C and 8 0? C water vat to test for how temperature affects denaturation. It can be record by the time assume for the first change of appearance.To find out how pH of affect denaturation, we can extend cut backwise the actetic irate to the egg white solution. Beside, the NaCl can also be add dropwise to egg white, to test for how salt concentration cause denaturation. forecast the number of drop of solution added for an appearance change to occur. Observation 60 ? C water bath After 15 minutes, a pallid yellow semi-solid formed 80 ?C water bath After 2 minutes 30 seconds, a white jelly uniform solid formed. 1M acetic acerb After 10 drops of acid added, the solution become pale yellow and clumping of egg white occurs 5M NaCl After 27 drops of NaCl added, the solution become yellow and clumping f egg white occurs check equal volume of water No observable change parole Protein? s three dimension conformation is held by the interaction between its amino acids. T his interaction included hydrogen bonds, ionic bonds and disulphride bonds. But in some extreme condition, such as broad(prenominal) temperature, extreme pH, high salt concentration, the protein leave be denaturate. It is because the cross linkage had been broken, the secondary and tertiary structure atomic number 18 alter.The protein now has primary structure as peptide bonds atomic number 18 strong enough not to be destructed. In our experiment, we observed that the egg white clump together subsequently denaturation (either by heat, pH or salt concentration). It is because after the normal structure is destructed, some new soldering may be formed between proteins. They can have a big clump of proteins hooked together. That is the coagulation. In coagulation process, the egg white turned from transparent to a cloudy solution, because as the protein clump together, in that location are no much space for light the pass through, so it looks more than cloudy. at any rate, in 80 ? C boiling tube, the egg white turned white while at 60 ? C the egg white only clump to a yellow semi-solid. It is because at high temperature more kinetic energy is provided for the molecules to vibrate, so the bondings are disrupted more greatly. So it can be concluded that a high temperature leave alone have a stronger effect on denaturation. Part B egg custard Aim To measure the phrase transitions that occurs in denaturation of egg and draw as affected by temperature change. PrincipleEgg and take out are the main ingredients of an egg custard, through baking an egg custard, we can examine the conformation transition of transition of denaturation of egg and milk as affected by temperature. Result After baking the egg custard for 30 minutes, the egg custard mess to a yellow flavourless gel. Discussion The egg custard is at silver mannikin before baking, and it turn to solid phase after baking. It shows that phase transitions of liquid to solid had occur in the denaturat ion process of egg and milk as affect by high temperature. The egg custard has a smooth and spongy texture.In the experiment, our egg custard is make of egg, milk, sugar only. Through applying of heat and manipulation, custards can become a viscous and semi-rigid gel, denaturation of the egg protein, causes a clumping of proteins, is primarily supply for the thickening of the custard. Milk, although not as important as egg, but atomic number 20 ions present in the milk are also needed in order to form thicker custard. Sugar is also important to the viscosity and gel competency of custards. Sugar tends to increase the denaturation temperature of the egg proteins conclusioning in less bolt custard.The concentration of egg protein is proportional to the viscosity or gel carriage of the custard. With increasing concentration, a custard sauce becomes more viscous and the gel strength of a baked custard firmer. A custard heated slowly begins to thicken at a lower temperature, thicken s gradually over a wider temperature range and result in a smoformer(a) texture. Slow cooking can be achieved by placing the custard mixture in a water bath to secure to certain temperature before put into the oven which has been skipped in our experimentPart C denaturation of milk Aim To examine the factors on the effect of denaturation of milk. Principle Milk protein, similar with egg white, will also undergo denaturation in extreme condition. So acid and NaCl is added to milk respectively, to observe the changes and examine how pH and salt concentration affect denaturation. Then, they are place in a 80 ? C water bath, also a take care tube is tube is put in water bath, to examine the effect of temperature on denaturation. Observation original milk pH= 6. 63 1 M acetic acid 60 drops of 1 m acid had been added The pH=4. 67 there are white ppt formed. Half quantity of 1 M acetic acid added 30 drops of 1M acid added there are no observable change. And after heat for 2 minutes, there are white boil down formed. 1 ml of 5M NaCl No observable changes soon after summing up of NaCl. There are little white precipitate after heat for 8 minutes. control No observable changes even after 20 minutes Centrifugation tube 3 layers formed.The upper layer is translucent, the middle one is white and the bottom layer is white precipitate. Discussion There are 3 layers present in the centrifugation tube after centrifugation. The upper layer is the acetic acid we added, the middle layer is the milky serum, the bottom layer is the precipitate formed bring out by the addition of acid. There are 2 major components of milk, casein and serum .The casein contains phosphorus and will coagulate or precipitate at about pH 4. 6. The serum proteins do not contain phosphorus, and these proteins remain in solution in milk at pH 4. 6. So, when acetic acid added the pH drop to 4. 69 the casein precipitate so white precipitate is seen. The addition of NaCl on ly cause a little precipitation, shows decrease in pH has a greater effect on milk denaturation than increase in salt concentration. There are no observable changes in control because the protein are not yet denaturated in 80 ? C.Part D yoghourt Aim To experience the making of yoghourt and the theory of formation of yoghourt. Principle As natural yogurt is make from fresh milk without other ingredient added, it can be made by simply add a little yoghurt and milk together and incubate in 38 ? C incubator, which is a suitable temperature to make yoghurt. Yoghurt can be available for tasting after 1-2 days. Results All milk turned into yoghurt, the sample is no longer liquid but is in semi-solid. The yoghurt is a bit sour than the original sample. DiscussionYoghurt is made by fresh milk, but often some specific bacterium strains are introduce into the milk. The bacteria ingest natural milk sugars and loosend lactic acid as a waste product. The acid decrease the pH and cause the denaturation of milk protein during which the cross linkage between protein break and protein uncoiled. Then, the protein will tangle into a solid mass, yoghurt formed In our experiment, we intricate the 50 ml milk with 5 ml yoghurt to made the sample yoghurt instead of milk only . the 5 ml yoghurt is to provide the bacteria.Only a small amount of live yoghurt can is needed to inoculate a new batch of yoghurt because the bacteria can reproduce and multiple themselves during the yoghurt making process. Besides the incubators temperature is 38 ? C because it is the optimum temperature of bacteria to reproduce. The yoghurt newly made is more sour than the original sample. It may be due to the long incubation hours, as we had kept it over 48 hours. The bacteria ingest a higher % of milk sugar and release more lactic acid. To stop the incubation we can place the yoghurt in a refrigerator.