# The effect of temperature on enzyme activity Watch

1. Hey,

So I'm conducting an experiment to investigate the effect of temperature on enzyme activity. I will be using free and immobilised enzymes at temperatures of 40 and 80 degrees celsius, and measuring the pH changes over a period of 12 minutes. This will help me to determine how fast the enzymes are working. (The enzymes will hydrolyse lipids, releasing fatty acids which decreases the pH, thus making the solution more acidic).

However I need to plot a graph of my results, and I really don't understand how to!

I have my time (minutes) plotted along the x axis, and pH along the y axis. Surely this means that over time, the pH will decline?

I'm confused because my teacher drew the line as if the pH was increasing (becoming more alkaline)? Surely this can't be correct?

Even if intermediate temperatures were used, such as 50 degrees celsius, surely the pH would still decline, but not as much as it would at the enzymes' optimum temperatures?

Can anyone explain this to me? Or has my teacher made an error?
2. (Original post by Lighfy)
Hey,

So I'm conducting an experiment to investigate the effect of temperature on enzyme activity. I will be using free and immobilised enzymes at temperatures of 40 and 80 degrees celsius, and measuring the pH changes over a period of 12 minutes. This will help me to determine how fast the enzymes are working. (The enzymes will hydrolyse lipids, releasing fatty acids which decreases the pH, thus making the solution more acidic).

However I need to plot a graph of my results, and I really don't understand how to!

I have my time (minutes) plotted along the x axis, and pH along the y axis. Surely this means that over time, the pH will decline?

I'm confused because my teacher drew the line as if the pH was increasing (becoming more alkaline)? Surely this can't be correct?

Even if intermediate temperatures were used, such as 50 degrees celsius, surely the pH would still decline, but not as much as it would at the enzymes' optimum temperatures?

Can anyone explain this to me? Or has my teacher made an error?

Hmm interesting.

I would've done the rate of hydrolysis or the concentration of product produced.

The x axis would definitely have temperature.

If you were to do pH then at a given temperature say above 40 degrees, the graph would line off as there is no longer a change in pH.

Do you have any results of this experiment?
3. (Original post by zed963)
Hmm interesting.

I would've done the rate of hydrolysis or the concentration of product produced.

The x axis would definitely have temperature.

If you were to do pH then at a given temperature say above 40 degrees, the graph would line off as there is no longer a change in pH.

Do you have any results of this experiment?
I'm doing the experiment on tuesday so unfortunately, no. My teacher drew the graph with temperature along the x axis and pH along the y axis, although that still doesn't really make sense to me as to why the pH would become more alkaline.

She then said that we'd just be measuring the pH at 40 and 80 degrees celsius, and so she said that time would be along the x axis, and we'd label which line was which. (For example, one line would be labelled as the "Free lipase at 40 degrees celsius")

I'll have to ask around on monday... Thank you for your help
4. (Original post by Lighfy)
I'm doing the experiment on tuesday so unfortunately, no. My teacher drew the graph with temperature along the x axis and pH along the y axis, although that still doesn't really make sense to me as to why the pH would become more alkaline.

She then said that we'd just be measuring the pH at 40 and 80 degrees celsius, and so time would be along the x axis, and we'd label which line was which. (For example, one line would be labelled as the "Free lipase at 40 degrees celsius")

I'll have to ask around on monday... Thank you for your help

I see.

The fatty acid should decrease the pH at around 40 degrees however at 80 degree the pH will not decrease further because I assume that the enzyme would have denatured by then hence the lipid cannot be hydrolysed.
5. (Original post by zed963)
I see.

The fatty acid should decrease the pH at around 40 degrees however at 80 degree the pH will not decrease further because I assume that the enzyme would have denatured by then hence the lipid cannot be hydrolysed.
Yep, the free lipase should denature however the immobilised lipase should still continue to decrease the pH as some will still have a complementary shape to the substrate.
6. hey I'm trying to answer this two mark question but don't know how to :/
the question is-

explain the difference in activity of free enzymes at 40 and 50 degrees
7. (Original post by Lighfy)
Hey,

So I'm conducting an experiment to investigate the effect of temperature on enzyme activity. I will be using free and immobilised enzymes at temperatures of 40 and 80 degrees celsius, and measuring the pH changes over a period of 12 minutes. This will help me to determine how fast the enzymes are working. (The enzymes will hydrolyse lipids, releasing fatty acids which decreases the pH, thus making the solution more acidic).

However I need to plot a graph of my results, and I really don't understand how to!

I have my time (minutes) plotted along the x axis, and pH along the y axis. Surely this means that over time, the pH will decline?

I'm confused because my teacher drew the line as if the pH was increasing (becoming more alkaline)? Surely this can't be correct?

Even if intermediate temperatures were used, such as 50 degrees celsius, surely the pH would still decline, but not as much as it would at the enzymes' optimum temperatures?

Can anyone explain this to me? Or has my teacher made an error?
Your teacher has made an error, unless they drew the pH decreasing going upwards then if the reaction makes the pH decrease then it would have a negative correlation the least it could do would be a straight line if all the enzymes have become denatured.
8. (Original post by L-JW)
Your teacher has made an error, unless they drew the pH decreasing going upwards then if the reaction makes the pH decrease then it would have a negative correlation the least it could do would be a straight line if all the enzymes have become denatured.
Yes, my teacher made an error! >.< All done and dusted now though, the line did in fact decrease on my graph Thanks.
9. (Original post by thestudent_09)
hey I'm trying to answer this two mark question but don't know how to :/
the question is-

explain the difference in activity of free enzymes at 40 and 50 degrees
You've probably already figured it out by now, but if not:

Higher temperatures will distort the tertiary structure of some of the free lipase, thus altering the shape of its active site. This means that the active site of some of the free lipase will no longer be a complementary shape to the substrate molecule and so some of the free lipase are inactive, thus the activity of free lipase decreases at higher temperatures.
10. (Original post by Lighfy)
You've probably already figured it out by now, but if not:

Higher temperatures will distort the tertiary structure of some of the free lipase, thus altering the shape of its active site. This means that the active site of some of the free lipase will no longer be a complementary shape to the substrate molecule and so some of the free lipase are inactive, thus the activity of free lipase decreases at higher temperatures.
Thank you! I did find out plus i just needed to make sense of how to write it down.
11. (Original post by thestudent_09)
Thank you! I did find out plus i just needed to make sense of how to write it down.
Oh okay was that for the A2 practical?
12. (Original post by Lighfy)
Oh okay was that for the A2 practical?
yup, for the quant and eval. i just wanted to make sure i include all the right things for the answer.
13. (Original post by Lighfy)
Hey,

So I'm conducting an experiment to investigate the effect of temperature on enzyme activity. I will be using free and immobilised enzymes at temperatures of 40 and 80 degrees celsius, and measuring the pH changes over a period of 12 minutes. This will help me to determine how fast the enzymes are working. (The enzymes will hydrolyse lipids, releasing fatty acids which decreases the pH, thus making the solution more acidic).

However I need to plot a graph of my results, and I really don't understand how to!

I have my time (minutes) plotted along the x axis, and pH along the y axis. Surely this means that over time, the pH will decline?

I'm confused because my teacher drew the line as if the pH was increasing (becoming more alkaline)? Surely this can't be correct?

Even if intermediate temperatures were used, such as 50 degrees celsius, surely the pH would still decline, but not as much as it would at the enzymes' optimum temperatures?

Can anyone explain this to me? Or has my teacher made an error?
Any ideas what the test for lipase is? I tried to search it but it keeps coming up with doing a blood test....

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