# Homework Help: Biology - Action of Pepsin

1. Sep 18, 2008

### LilaK

I have to write up a lab related to pepsin. I did an experiment in class but unfortunately it did not turn out how I wanted it to be and I did not collect my results properly. Maybe someone has done a pepsin experiment before and could help me out.

This is what I thought of for my new experiment but I don't have results. Its just an idea but please give me another pepsin related experiment if you can.

Aim of the experiment:
The aim of this experiment is to test whether temperature affects the rate of which pepsin reacts to egg albumin (Source of protein).

Hypothesis:
“If the temperature varies, then the rate at which the pepsin digests egg albumin will change”.

Variables:
Independent Variable – Temperature range.
Dependent Variable – Rate at which the pepsin digests the egg albumin.
Constant Variables – amount of pepsin, amount of rare egg white, amount of acid, temperature, stopwatch.

Last edited: Sep 18, 2008
2. Sep 18, 2008

### Moonbear

Staff Emeritus
How did you determine the experiment did not turn out right? The most important lesson you might ever learn about science is that experiments don't always turn out as expected. That doesn't mean they didn't work.

Are you expected to write up your lab report on your ACTUAL results? If so, post a summary of those here so you can get proper help.

3. Sep 18, 2008

### LilaK

Prediction:
In this experiment I declare that my hypothesis will be true, as indeed the egg albumin will be influenced by temperature. This experiment should function to it’s best in the water bath which is situated around 35 degrees Celsius. The reason for this is due to the fact that the body temperature is situated around that same temperature, and which pepsin functions at its optimum best in.

Method:
I have created a procedure of which allows me to test the effect of temperature on the rate of digestion of pepsin upon egg albumin. The four varied temperature are the following:
Ice temperature (0-5 degrees Celsius):
Boiling (90 degrees Celsius):
Water bath (37 degrees Celsius):
Room temperature (20 degrees Celsius):

I just need a rough idea of what the results would be because I was not able to collect them because I made the observations too late so it would not have been a fair test. I also need to have an idea what the conclusion for this experiment should be. Please help me out, I would really appreciate it.

4. Sep 20, 2008

### Moonbear

Staff Emeritus
First, you need to work on refining your predictions. The second sentence there is closest to what a prediction should be, but you need to make it clearer of what you'd expect if your hypothesis is true. What do you mean by "This experiment should function to its best...?" If 35 degrees is optimal, what would your results look like?

I still don't understand why you think it's not fair? Did you let them all run the same amount of time? If so, it was fair. It's only a problem if you stopped them at different times and introduced more than one variable (time and temperature). Otherwise, you still have results to work with.

I think that's what you're supposed to be learning to figure out on your own. Here are some hints.

If you have good reason to think you'd get different results if you stopped the reaction sooner, then explain that in your discussion. You still should work with the actual results you got until then. Consider all your options, and discuss them one at a time as possible interpretations. One of those interpretations might be the one you're talking about here, that the reaction went too long and you didn't get any differences because of it. What's another interpretation? The primary conclusion should be based on the results you really got. Does it fit your prediction or not? (This is why writing a good hypothesis and prediction is important...it makes it a lot easier to draw a conclusion when done.)

Yes, in the real world of science, you would repeat the experiment while systematically changing other conditions, such as time in addition to temperature to see if there is a time dependence. But that's not what you did for the class. For a class project, your conclusions should be based just on what you were assigned to do, and just discuss any alternative interpretations to show you're thinking about those other variables too.