HELLLP

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Re: HELLLP

Postby donnahardy2 » Sun Feb 03, 2013 9:41 am

Hi Daven,

I think you are doing this really great project from the Science Buddies website:

http://www.sciencebuddies.org/science-f ... #procedure

You have a very good question. Step 9b describes the dilution of your antifungal. The first step, adding 1/8 tsp antifungal to 9/8 tsp water is a 1:10 dilution. The next step, taking 1/8 tsp of the 1:10 dilution in 1/4 cup of warm water with sugar is a 1:100 dilution, so the final dilution is 1:1000 for the high concentration sample or 10 ug/mL

The procedure then suggests diluting the 1:1000 dilution by adding 1/8 tsp of the 1:1000 dilution to 1/14 cup of water with sugar. So the low concentration sample is 1:1000 x 1:100, or 1:100,000, or 0.1 ug/mL.

This is an example of of a dilution for a 1% antifungal. The procedure suggests checking the literature to find out what the effective concentration of the antifungal you will be working with. What antifungal agents are you testing?

If you followed this procedure and measured the amount of carbon dioxide produced, then your results are correct. When you do a science experiments until controlled conditions, your results are never incorrect.

However, if you obtained results that don't seem to make sense, please let us know what antifungal you used, what you did, and what your results were. Did you run a control with no antifungal? Did you repeat your results?

Please post again and explain why you are concerned about your results.

Donna Hardy
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Re: HELLLP

Postby donnahardy2 » Sun Feb 03, 2013 6:06 pm

Hi Daven,

Sorry, the 1/14 is a typo. The 1:1000 dilution is one-eighth teaspoon of the 1:10 dilution of the antifungal in one quarter cup water.

It sounds like you observed no gas production in the low dilution of all of the antifungals. Lack of gas production indicates that the yeast were inhibited and were not metabolizing the sugar, and this is a possibility.

Can you confirm that you made the low dilutions in sugar water and that these samples also contained yeast?
Was there gas production in the control sample with no antifungal added?
Was there gas production in the 1:1000 dilution sample?

Was your first dilution of the antifungal 1/8 tsp antifungal plus 9/8 tsp water?
Was your second dilution (high concentration) 1/8 tsp of the first dilution plus 1/4 water with sugar and yeast?
Was your third dilution (low concentration) 1/8 tsp of the second dilution plus 1/4 water with sugar and yeast added?

Was the temperature the same for every trial?
Did you add the same amount of yeast and sugar to every sample?


Please answer the questions as this may help me understand what is happening in your experiment. I've looked at the procedure again and it is fairly detailed, so I'm not sure what's wrong.

Do you have access to a balance and containers that will allow you to measure using metric measurements? For example, weigh 1 gram of antifungal and all 10 milliliters of water? This would help you understand the dilutions better.


Donna Hardy
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Re: Help!

Postby donnahardy2 » Sun Feb 03, 2013 6:10 pm

Hi Daven,

I just answered this question in your original topic. It's better to always post a reply in the same topic so the experts following your topic will be notified.

Donna Hardy
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Re: HELLLP

Postby donnahardy2 » Mon Feb 04, 2013 5:41 pm

Hi Daven,

Thanks for answering the questions.

The directions include an initial 1:10 dilution of the antifungal in water, so you started with a 1:100 dilution. Your second dilution was a 1:100 x 1:100, or a 1:100,000 dilution. This is fine; for your project board, you just need to report what you actually did.

You observed gas in the 1:100 dilution, so the yeast were metabolizing in the more concentrated dilution. I would expect that you would observe more gas production in the 1:100,000 dilution as the antifungal was less concentrated in this sample. Is this what happened?

You did a good job of keeping all other parameters controlled, temperature, and the quantity of yeast and sugar, so the only difference in the samples was the concentration of antifungal so you should be able to quantitatively compare the amount of gas in each sample.

Since you did not answer the question about the gas production in the control sample, I am guessing that you did not test a sample with just yeast and sugar (no antifungal). If this is the case, I recommend that you set up this control so you can compare gas production of the antifungals with the control sample. Your project is due soon, and you should be concentrating on writing up your project board, but the negative control sample is essential for your experiment.

Please post the quantity of gas production in each concentration of the antifungals you used? I am very interested in seeing your data.

I hope this helps. Did all of my comments make sense? If not, let me know if you have questions.


Donna Hardy
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Re: HELLLP

Postby donnahardy2 » Thu Feb 07, 2013 8:48 am

Hi Daven,

You are correct about the objective for this experiment; if the yeast are inhibited by the antifungal, they will produce less gas. So you results are interesting; if you obtained 1 to 3 cm of gas with the high concentration, then I normally expect more gas production with a lower concentration of antifungal.

I’m not sure what happened with your experiment, but normally, results like this can be explained by repeating the experiment and including a control. Since you do have a little time, I would recommend repeating your results with one of the antifungals and include a control with yeast and sugar that does not contain any antifungal. The control will be your baseline for gas production and you will be able to quantitatively compare results to the samples with different concentrations of the antifungal.

Depending on the results, you can then decide to repeat the results with the other antifungals. Let me know what happens.

Donna Hardy
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Re: HELLLP

Postby donnahardy2 » Thu Feb 07, 2013 5:15 pm

Hi Daven,

The quantities of gas are relative and you won’t know how many centimeters will be produced until you do the experiment. The amount of gas produced depends on the number of yeast cells, the temperature, time and oxygen availability, but you have to do the experiment to get the answer.

It would be helpful to know what volume of gas is being produced. What is the diameter of your collection container? Can you calculate the volume based on the centimeters of gas produced?

You will be measuring centimeters (or volume) of gas for the control and for each dilution of the antifungal. You will be able to calculate the percentage of gas produced in each sample compared to the control.

How are you going to present your results? What kind of a graph are you planning to use?

Donna Hardy
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Re: HELLLP

Postby donnahardy2 » Sun Feb 10, 2013 9:21 am

Hi,

I would recommend doing a bar graph for your data. For each sample, you would have one bar for the control results and one for each dilution:

Here is a site that will help you make a bar graph.

http://nces.ed.gov/nceskids/graphing/cl ... rtType=bar

Here is the information from the Science Buddies website on presenting your data.

http://www.sciencebuddies.org/science-f ... checklists

It would be great to record the production of gas as a function of time and do a line graph but I think the bar graph would be a clearer way to present your data.

Donna Hardy
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