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What are the effects of enzyme exposure to high temperatures?

What are the effects of enzyme exposure to high temperatures?


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Question: After enzymes are exposed to high temperatures and undergo denaturation, then returned to their optimal temperature and renatured, can the enzyme's active site return to it's original shape and will it function at the same level of efficiency as it did before being denatured and renatured?

Some background I wrote to the question: I am just beginning to learn Cell Biology, I hope what I've written is correct.

When you raise the temperature of an enzyme, at first it will increase the efficiency of the enzyme's activity, but eventually as the temperature rises, the enzyme with stop functioning and undergo denaturation, which means that the 3D formation of the protein is unraveled, so it doesn't function anymore. From what I've managed to research, the high temperature changes the shape of the active site in the enzyme, which is what allows the enzyme's activity in the first place. I know that some proteins cannot be renatured (like adding heat to an egg will fry it and there is no way to unfry it), but some can be renatured (like heated milk, when it cools down the protein bonds will reestablish themselves).

But will the enzyme's active site return to it's original shape and manage to function at the same level of efficiency as it did before? Or is the damage permanent?


The answer is that it completely depends on what specific enzyme you're talking about; some of them will and some of them won't. What you wrote is correct, that increasing temperature of most enzymes (although there are exceptions) will increase their activity to a certain point, after which the proteins lose their 3D structure and become unfolded.

Upon cooling, it all depends on whether the enzyme can re-fold by itself or not. Some proteins when heated form aggregates, which are more stable than the original conformation, and so generally won't refold with cooling. Some proteins are able to fold into proper conformation by themselves, while other require assistance from chaperone proteins in order to fold correctly. Many of these chaperones are called heat-shock proteins, which are upregulated in response to thermal stress. That points to the fact that many proteins can't just refold on their own, and require help to regain their original conformation from these HSPs.

So the real answer is that it all depends on the specific protein. It also depends on how much you heat the enzyme, and how much of its 3D structure you affect, if you only partially denature an enzyme, it's more likely to refold than one that's been completely denatured. However, if you want an answer about enzymes in general, I'd say that most enzymes after denaturation aren't able to refold properly and regain their enzymatic activity, so the damage is permanent.


Do high temperatures enhance the negative effects of ultraviolet-B radiation in embryonic and larval amphibians?

For the embryos and tadpoles of amphibian species, exposure to ultraviolet-B radiation (UVBR) can be lethal, or cause a variety of sublethal effects. Low temperatures enhance the detrimental effects of UVBR and this is most likely because the enzyme-mediated processes involved in the repair of UVBR-induced damage function less effectively at low temperatures. Whether these repair processes are also impaired, and thus the negative effects of UVBR similarly enhanced, at high temperatures is not known, but is an ecologically relevant question to ask given that organisms that inhabit environments where the temperature fluctuates widely on a daily timescale are likely to experience high doses of UVBR when temperatures are high. Here we examined the thermal-dependence of UVBR effects in the context of an ecologically-relevant fluctuating UVBR and temperature regime to test the hypothesis that exposure to peak UVBR levels while the temperature is high (35ଌ) is more detrimental to embryonic and larval Limnodynastes peronii than exposure to peak UVBR levels while the temperature is moderate (25ଌ). Embryos exposed to peak UVBR levels at 35ଌ hatched 10 h later than those exposed to peak UVBR levels at 25ଌ and, as tadpoles, were smaller and consequently swam more slowly but, in an environment with predators, exhibited no difference in survival time. There was also no effect of experimental treatment on the hatching success of embryos, nor on the post-hatch survival of tadpoles. These findings, therefore, are not sufficiently strong to support our hypothesis that high temperatures enhance the negative effects of UVBR in embryonic and larval amphibians.


How Does Temperature Affect Catalase Enzyme Activity?

In general, the rates of enzyme-catalyzed reactions are faster as temperature increases and slower as temperatures decrease below an optimal temperature level. When temperature increases, more molecules have more kinetic energy to react, so reaction speed increases. As temperature decreases, so does the available energy, and then the reaction is slowed.

A variation in temperature as little as 1 or 2 degrees Celsius can increase an enzyme-catalyzed reaction rate by 10 to 20 percent. Raising the temperature 10 degrees increases the activity rate of most enzymes by 50 to 100 percent. There is an exception is when temperatures reach a certain threshold above the optimal temperature level. When this happens, the intermolecular attractions that maintain the shapes of proteins are broken and the enzyme molecule's shape changes. This results in decreased binding of reactants and a significant decrease in enzyme activity. At this point, the enzyme is said to be denatured. Many enzymes are denatured when temperatures exceed 40 to 50 degrees C (104 to 122 F). Extremely cold temperatures also significantly slows reaction rate.

The effect of temperature on the rates of enzyme-catalyzed reactions is exactly why food is refrigerated. A refrigerator's cooler environment slows the enzyme-catalyzed reactions that result in food spoilage. Of course, freezing food slows those reactions even further. Other factors that influence the rates of enzyme-catalyzed reactions include surface area, pH and light.


N. A. Korotina, “Comparison of enzyme activity of the small intestine during exposure to a high ambient temperature and after injection of pituitary hormones,” Abstracts of Proceedings of the Second Conference of Physiologists of Uzbekistan [in Russian], Tashkent (1973), p. 128.

S. N. Safarova, “The effect of exposure to a high ambient temperature and to sunlight on the enzyme activity of the pancreas and intestine,” Author's Abstract of Candidate's Dissertation, Tashkent (1967).

A. M. Ugolev and N. N. Iezuitova, “Determination of the activity of invertase and other disaccharidases,” in: Investigation of the Digestive System in Man [in Russian], Leningrad (1969), p. 192.

A. M. Ugolev and N. M. Timofeeva, “Determination of peptidase activity,” in: Investigation of the Digestive System in Man [in Russian], Leningrad (1969), p. 178.

A. M. Ugolev and M. Yu. Chernyakhovskaya, “Determination of the final stages of hydrolysis of triglycerides,” in: Investigation of the Digestive System in Man [in Russian], Leningrad (1969), p. 183.

A. M. Ugolev, N. M. Timofeeva, N. N. Iezuitova, et al., “Changes in the contact (membrane) digestion during exposure of the organism to stress factors,” in: Problems in the Prevention and Treatment of Diseases of the Digestive Organs [in Russian] Chernovtsy (1970), p. 328.

C. Fiske and J. Subbarow, cited by. A. M. Ugolev, Contact Digestion, Polysubstrate Processes, Organization and Regulation [in Russian], Nauka, Leningrad (1972).


What Is The Effect Of Temperature On Enzyme Activity?

The higher the temperature is, the higher the rate of the enzyme reaction becomes, as it increases, and heat is produced. It has an optimum temperature of where it works best at 37 to 40 C, but after 40 C the enzyme gets denatured and no longer works properly, particularly in animal ones.

When the temperature rises, there are more energetic collisions between the enzymes within the reaction. The number of these per minute will also increase, along with the heat of the molecules.

Many experiments have been done in labs across the world, testing the results of enzyme activities. They have found some great answers, which help give proof to biology and how our body’s work as well as those of animals and plants.

Most enzyme reactions are often done below 40 C in order to give them a good efficiency and not denature them. If they get denatured, then they are damaged and no longer fit into each other to create a reaction.

Enzymes can be stored at 5 C or below, although some of them lose their effectiveness if they get too cold. This is why humans and most animals cannot get too cold or too hot, above 40 C, as it will denature many enzymes within the body, and therefore stop its functions.

This will lead to serious illness and even death. It is important to keep the body at the optimum temperature of around 37 C in order for them to work best, and keep it fit and healthy.

Temperature can affect a lot of different factors hence its effect on enzyme activity is very complex. It affects the speeds of molecules, the activation energy of the catalytic reaction and the thermal stability of the enzyme and substrate.

At low temperatures (say at around 0 centigrade) the rate of enzyme reaction is very slow. The molecules have low kinetic energy and collisions between them are less frequent and even if they do collide the molecules do not posses the minimum activation energy required for the reaction to occur. It can be said that the enzymes are deactivated at low temperatures.

An increase in temperature increases the enzyme activity since the molecules now possess greater kinetic energy. The rate of enzyme activity is highest between 0-40 centigrade and this increase is almost linear.

After 40 the rate of reaction starts to decrease. This is because the increase in temperature after 40 does not increase the kinetic energy of the enzyme but instead disrupts the forces maintaining the shape of the molecule. The enzyme molecules are gradually denatured causing the shape of the active site to change. Temperatures above 65 centigrade completely denature the enzymes.

There are some enzymes known as 'extremophiles' found in thermophillic organisms. They retain activity at 80 centigrade.


What are the effects of enzyme exposure to high temperatures? - Biology

Summary For the embryos and tadpoles of amphibian species, exposure to ultraviolet-B radiation (UVBR) can be lethal, or cause a variety of sublethal effects. Low temperatures enhance the detrimental effects of UVBR and this is most likely because the enzyme-mediated processes involved in the repair of UVBR-induced damage function less effectively at low temperatures. Whether these repair processes are also impaired, and thus the negative effects of UVBR similarly enhanced, at high temperatures is not known, but is an ecologically relevant question to ask given that organisms that inhabit environments where the temperature fluctuates widely on a daily timescale are likely to experience high doses of UVBR when temperatures are high. Here we examined the thermal-dependence of UVBR effects in the context of an ecologically-relevant fluctuating UVBR and temperature regime to test the hypothesis that exposure to peak UVBR levels while the temperature is high (35°C) is more detrimental to embryonic and larval Limnodynastes peronii than exposure to peak UVBR levels while the temperature is moderate (25°C). Embryos exposed to peak UVBR levels at 35°C hatched 10 h later than those exposed to peak UVBR levels at 25°C and, as tadpoles, were smaller and consequently swam more slowly but, in an environment with predators, exhibited no difference in survival time. There was also no effect of experimental treatment on the hatching success of embryos, nor on the post-hatch survival of tadpoles. These findings, therefore, are not sufficiently strong to support our hypothesis that high temperatures enhance the negative effects of UVBR in embryonic and larval amphibians


Why do enzymes stop working at high temperatures?

Enzymes are biological catalysts. This means they spead up chemical reactions in the body. To understand why they might stop working, you must first look at the structure. Enzymes are proteins made up of primary, secondary and tertiary structures to give their complex final shape. The primary structure is made up of a sequence of amino acids. The secondary structure is formed by hydrogen bonds between the amino acids, and the tertiary structure is a 3D structure produced by interations of the amino acid side chains.

The bonds and interations making up the teriary structure of the enzyme are sensitive to heat. In different temperatures, these bonds can change. If an enzyme is used in the human digestive system (e.g. amylase), it will work best at body temperature of 37 degrees. In high temperatures, the bonds of the enzyme will be altered and the structure of the enzyme will change. This means the active site (where the substrates interact), will be a different shape. The substrates will not fit this new shape and thus, the enzyme will no longer work. It is denatured.


The Effect Of Temperature On An Enzyme-Catalysed Reaction

Aim

To investigate the effect of temperature on the initial rate of an enzyme-catalysed reaction.

Independent Variable

Temperature of each enzyme solution (water baths at 10°C, 20°C, 30°C, 40°C and 50°C will be used)

Dependent Variable

Time taken for the solution to turn pink (measured in seconds using a stopwatch)

Control Variables

  • Volume of enzyme solution – 1cm³ of the lipase enzyme solution will be used each time, measured using a syringe
  • Volume of milk – 5cm³ of milk will be used each time, measured using a measuring cylinder
  • Volume of sodium carbonate solution – 7cm³ of the solution will be used each time, measured using a measuring cylinder
  • Volume of phenolphthalein added- 5 drops will be added each time using a pipette
  • Colour of solution – the stopwatch will be stopped each time when the solution is completely colourless

Equipment

  • Water baths
  • Milk (full-fat)
  • Phenolphthalein
  • 5% lipase solution
  • 0.05M sodium carbonate solution
  • Hot water baths
  • Test tube racks
  • Thermometer
  • 5 beakers
  • 5 test tubes
  • Marker pen
  • Measuring cylinder
  • Pipette
  • Syringe
  • Glass rod
  • stopwatch

Control

A set-up can involve carrying out and timing the reaction at room temperature as a negative control. The results can then be compared to this standard.

Method

  1. Set up the water baths at 10°C, 20°C, 30°C, 40°C and 50°C and put a beaker of lipase, containing a 2 cm 3 syringe into each water bath.
  2. Label a test tube with the temperature to be investigated.
  3. Add 5 drops of phenolphthalein to the test tube.
  4. Measure out 5 cm 3 of milk using a measuring cylinder and add this to the test tube.
  5. Measure out 7 cm 3 of sodium carbonate solution using another measuring cylinder and add this to the test tube. The solution should be pink.
  6. Place a thermometer in the test tube. Take care as the equipment could topple over.
  7. Place the test tube in a water bath and leave until the contents reach the same temperature as the water bath.
  8. Remove the thermometer from the test tube and replace it with a glass rod.
  9. Use the 2 cm 3 syringe to measure out 1 cm 3 of lipase from the beaker in the water bath for the temperature you are investigating.
  10. Add the lipase to the test tube and start the stopwatch.
  11. Stir the contents of the test tube until the solution loses its pink colour. Stop the watch and note the time in a suitable table of results.

Results & Calculations

A graph can be made where initial rate (1/T) can be plotted on the y-axis and temperature on the x-axis. You should see a graph looking similar to this:

A Q10 value can also be calculated for this reaction using the data below the optimum temperatures. The equation for Q10 is as follows:

(Rate of reaction at temperature + 10°C) ÷ (Rate of reaction at temperature T)

A Q10 value of 2 means that for every increase in 10°C, the initial rate doubles. Likewise, a value of 3 means that every increase in 10°C triples the initial rate and so on. This deduction only works for temperatures up to the optimum temperature.

Conclusion

The peak of the graph indicates the optimum temperature. This is when enzymes have the greatest amount of kinetic energy they can have whilst maintaining their protein structure. At this point, the enzymes are working most efficiently and effectively.

Beyond this optimum temperature the protein structure starts to change. Large amounts of kinetic energy overcome the hydrogen bonds in the tertiary and secondary structures of the proteins. This causes the enzyme to change shape and so the shape of the active site is also altered. For this reason, fewer substrates can bind to form enzyme-substrate complexes. This is why increasing the temperature beyond a certain point slows down the rate of reaction.


2 Nice And Comfortable

Enzymes, like any other proteins, have specific 3D shapes that only exist at certain temperatures that they find comfortable. Enzymes of the human body maintain their normal shape and activity at around normal body temperature, about 37.5 degrees Celsius. Increasing the temperature increases the speed at which the atoms within an enzyme vibrate. Too much vibration causes the intermolecular interactions that hold the enzyme’s 3D shape to fall apart, which causes the enzyme to change its shape, including the shape of its active site. Thus, enzyme activity is completely abolished due to boiling. Most animal enzymes will denature, or unfold, starting at 40 degrees Celsius.


Discussion:

Based on the aforementioned experiment, the effect of different concentrations of enzyme on the speed of reaction is successfully established. Five graphs are plotted based on the results obtained in the experiment to show the data in a clearer way and provides a better mean for analysing. The results show that the rate of effect is increased by a rise in enzyme focus. In this experiment, potato can be used as way to obtain catalyse. The first four graphs showing oxygen gas developed against time are drawn based on particular mass of blended potato used. The original rate of effect is measured from each graph by obtaining the gradient of the graph. A predicted lines is drawn on each graph. Generally, the longer enough time taken, the higher the quantity of air gas evolved. Initially, all graphs show an speedy increase, the speed is the decelerate as some of the substrates are changed into products. For the substrate at 1 and 2 g of bended potato used, the maximum volume of air gas evolved has reached within 300 mere seconds and a plateau is obtained. It is because the effect has completed for all substrates. Theoretically, the utmost volume of air gas released should requires a shorter time as compared to 1g and 2 g of potato as more active site can be found. However, Inside the 3 and 4 g of blended potato which react, the maximum level of oxygen struggles to be obtained within 300 secs. That is probably due for some errors conducted throughout the test, particularly because of the vigorous and swift reaction and along the way of changing the graduated pipe. The mistakes will be reviewed later. The original rate is considered because the speed of reaction is swift as the collision between the substrate and enzyme is the best. The speed of reaction may well not be reliable to be compared between data if readings are used the middle of the experiment because some reactions have reached the utmost rate. The original rate of response for hydrogen peroxide with 1g, 2g, 3g and 4g of blended potatoes are 0. 0611, 0. 2895, 0. 6579 and 0. 7000 cm3/ s respectively.

The primary rate of reactions for all your tests are then compiled into the fifth graph. This shows a clearer picture on the result of attention of substrate on the speed of reaction. Primarily, there can be an increase in the pace of response when the mass of blended potato increases. This is because the upsurge in the focus of enzyme offers more active site for the binding of substrate. Then, the slope of increasing collection becomes less steep with further upsurge in attention of enzyme. It is because the active site has been occupied by the substrates or it is said to be saturated whereby the increase in substrate has no further effect on the speed of reaction. Theoretically, the graph should reach a maximum velocity where the plateau occurs in the graph. However, in this experiment, the plateau is not shown because most probably the concentration of enzyme is not high enough to bind to all or any the 3. 0 % of hydrogen peroxide substrate.

However, throughout the test some errors might occur in which the real values might not exactly be obtained. First of all, there's a high propensity for the reading obtained from water displacement solution to be inaccurate specially when the quantity of oxygen gas improved are too much that the first graduated tube is fully filled with oxygen gas so when the delivery pipe has to be transferred to the next prior-prepared graduated tube. The delivery tube transferring process may ingest some time especially if a plastic delivery tube is utilized rather than a wine glass delivery pipe. This will cause a few of the oxygen gas to flee into the drinking water through the process. Next, parallax problem might occur as well when the reading is extracted from the graduated tube on the volume of air gas evolved. This is because air gas is a colourless gas, where its level is not so clearly seen on the calibration of the graduated pipe. To minimise the errors, the experiment is repeated double and the mean reading is obtained. To help expand increase the accuracy and reliability of the results, a piece of white newspaper can be placed behind the graduated tube to make the reading easier. Next, the possible mistake is increased if the test is carried out individually. That is due to the human limited capacity to record the reading and at exactly the same time watch over enough time. Inaccuracy may arise. In cases like this, a pair work is preferred in this test among the associates times and the other one record the readings obtained. Next, when the mashed potato is poured in to the boiling pipe from the weighing dish, some potato may be remaining in the weighing dish. To minimise this mistake, a few drops of distilled water may be used to rinse out the weighing dish to ensure there is no residue still left.

Consequently, there are a few precautions that should be taken to increase the correctness of the results obtained. For every experiment, the potato used must be newly mashed or combined. If the potato is prepared in a box, the lid of the pot should be kept closed following the desired mass of blended potato is scooped out for each and every experiment. The planning of blended potato in a beaker which is subjected to mid-air should be prevented because oxidation will appear which may affect the activity of enzyme catalase in it. Changes in bordering such as heat range may also cause changes in the enzyme. A blended potato is utilized instead of discs of potato such that it will respond easier. Its viscosity should be reduced such that it is better to use. Next, hydrogen peroxide must be stored in an opaque container as it breaks down quickly when exposed to light. The lid of the container that contains hydrogen peroxide solution should be maintained closed after every desired test is taken out utilizing a dropper as the air in the surrounding air may oxidise its content and causes the results to be inaccurate. A buffer solution is utilized to guarantee the pH is kept constant throughout the experiment. The buffer solution of citric acid sodium phosphate solution which has a pH of 6. 8 is used because this is the perfect pH for the enzyme catalase. Furthermore, a drinking water bath is preferable as the surrounding heat range may change throughout the test. Furthermore, as the silicone bung of the delivery tube should be of the same size as the boiling pipe to ensure all the beginning of the boiling pipe including enzyme and substrate is fit firmly, it ought to be pushed and twisted carefully. It will also be examined from time to time to ensure there is absolutely no leakage of product in gaseous form to the encompassing. Besides, the other open end of delivery pipe should be located in water all the time for the bubble of gas to form and rise to its surface. The presence of air bubbles ensure that the silicone bung continues to be in contact with the boiling pipe unless the substrate and enzyme has completely reacted. To repair the graduated tube set up, a retort stand and clamp can be utilized. Besides, the boiling tube including reactants and enzyme should be swirled throughout the test to ensure the substrate and enzyme react. This might boost the rate of collision between your reactants and enzymes and thus fasten the time taken for the a reaction to complete.

Throughout the experiment, some safety measures should be abided by. As the substrate used in this test which is hydrogen peroxide is highly corrosive, silicone glove should be utilized to protect the skin. Following the hydrogen peroxide can be used, it ought to be disposed off and not to be came back to stock containers as any pollutants may result in decomposition and explosion may occur. The combined potatoes have to be taken care of carefully as well as it'll aggravate some people's skin. A lab jacket should be placed on. The goblet wares and the delivery tube used should be handled carefully because they are fragile.


Watch the video: GCSE Science Revision Biology Effect of Temperature and pH on Enzymes (September 2022).