Yeast metabolism with and without aeration

[MauJec10]

Hi Science friends,

I totally get how to do my project but its the fine detail that im concerned with. Like the control and the independent and dependent variables. i got my project actually from here but im having a hard time figuring these things out. my teacher asked me what the big picture was, like why im doing this project, what's the point. and i struggle to answer that question too. how exactly do i relate this to actual life, the real world?? help please.

thanx,
Bio student

[barretttomlinson]

Hi,

I am guessing that the project you are trying to do is this one:

https://www.sciencebuddies.org/science- ... g&from=TSW

Have you carefully read the whole writeup, especially the introduction part, and have you looked at the web links in the bibliography? These talk about the different forms of cell respiration, with and without oxygen.

In real life, yeast is vital to making bread and wine, beer, and other alcoholic beverages. Certain kinds of yeast can also cause some kinds of infections(search google on candida or candidiasis). So knowing about the conditions under which yeast thrives or dies or produces alcohol might be extremely important to success in making bread or wine or curing a yeast infection.

Have you read the Science Buddies Project Guide?

https://www.sciencebuddies.org/science- ... ndex.shtml

It might help answer your issues with variables (see the pages under Constructing a hypothesis), as well as answering a lot of questions on how to execute and report a science project.

Hope this helps a little. This is a very good practical science project - have fun with it!

Best Regards,

Barrett Tomlinson

[sciencebuddy]

Hey Bio student,
It's important to understand the concept of a control and independent/dependent variables before being able to apply it to your project.

The control: In a controlled experiment, the controls allow you to study one variable at a time and determine its effects. The control is a given condition that is present in every single experiment so that you can know for sure that only the variable is causing a change in results, not anything else. In your case, controls (or the conditions that must remain the same) would be the type and amount of yeast, water, and sugar, volume of the container, temperature of water, etc. Basically, whatever is done in one experiment must be done in the other EXCEPT for the variable, the presence of oxygen or lack thereof.

The independent variable: the variable that you are changing. It answers the question "What do I change?" In your case, it is oxygen.
The dependent variable: the results of an experiment because of the independent variable. It answers the question "What do I observe?" In your case, the yeast metabolism, measured by carbon dioxide output.

Hope this helps!

-Dan

[MauJec10]

Thanx so much!! To both of the people that have answered my post, im wicked grateful. I was thinking all night to figure out my project details, and the thing about bread did come to mind (not the wine lol). But i wasn't sure. Of course im going to do alittle more reading on yeast. i've decided to take another approach however. My teacher suggested that i take a slightly more advanced approach to the project (mostly because im an AP student here). She said that controlling the anaerobic part of the project would be difficult so i should make all of the test tubes (im using test tubes) aerobic and use different isomers of the same disaccharide. (im talking about the sugar) I don't completely remember what that means but i like the angle that she's putting me in the direction of. And plus, this way ill be measuring the CO2 made and ill be investigating whether or not the amount of CO2 is the same if they have different isomers. What do you think, im interested in your thoughts

thanx again,
Bio student

[Craig_Bridge]

teacher...said that controlling the anaerobic part of the project would be difficult

I agree with your teacher as many have failed trying that aspect.

use different isomers of the same disaccharide...investigating whether or not the amount of CO2 is the same

That should be an interesting and potentially challenging investigation. The yeasts may prefer one isomer over the other or there maybe different amounts of energy available. The challenge may come from figuring out what it takes to keep the pressure and temperature constant as the different isomers may have different reaction rate/reaction efficiency vs temperature/pressure behaviors.

[ChrisG]

Hi MauJec10,
I'm moving your topic over to the Life, Earth and Social Sciences forum where it will get some additional attention from our microbiology specialists.
I think your teacher's idea is a good one. What types of data would you plan to collect to address the question of rates and/or yield of CO2 from various disaccharides?
Looking forward to hearing more,
Chris

[MauJec10]

Hi science buddies,
Im going to be keeping the water temp constant after i boil it to make the sugar solutions. but i think the angle that you're looking at is the yeast and sugar solution?? right. umm could you explain what u mean more?? see my project paper work is completed, as in ive presented my topic and mode of investigation (procedure) to the state. im pretty sure i can modify little things as i go just to make things more precise and accurate. i want all my variables to be in line and now that you bring up watching to keep the temp/pressure constant and the possible different reaction rates, im a little concerned as to how i would accomplish controlling that. ill bring it to my teacher tomorrow and see what she thinks. Now the other big question that was brought up was

what types of data would you plan to collect to address the question of rates and/or yield of CO2 from various dissaccharides?

honestly im not completely sure. I'll think it out tonight and see what my teacher thinks of it tomorrow. Again i really appreciate my topic being moved for better viewing and the fact that it's getting any attention at all. Im more than grateful.

Thanx,
Bio Student

[donnahardy2]

Hi Bio Student,

We apologize for the delay in responding. I think after your topic was moved to life science, none of us realized no one was responding to your questions.

In reading through the posts, I gather that you will be making a number of containers to grow yeast in and that the only variable will be the type of sugar. The composition of the growth medium, the temperature, the amount of oxygen, and everything else should remain constant. Is this correct? I would be very helpful if you could post your purpose and hypothesis, and include the experimental details. What yeast are you using?

It seems that your main question is what you are going to measure. Here are some suggestions:

1. Use an inverted test tube in each culture and measure the volume of carbon dioxide produced over time. If you mark the volume on the test tube (upside down), you can measure the production of carbon dioxide at different times.

2. Measure the number of cells at difference time points by using optical density at 660 nm (with a spectrophotometer) or with a microscope using a hemocytometer.

http://www.pangloss.com/seidel/Protocols/ODvsCells.html

http://books.google.com/books?id=HoNOcB ... &ct=result

3. Centrifuge part of each sample and measure the cell volume/ milliliter.

I hope this helps. This should be a really great project.

Donna Hardy

[eknobs3]

I have a quick question about one of the procedures listed for this project. I'm going directly by the procedures listed on this site for the yeast metabolism with and without aeration project, and I'm uncertain as to where the other end of the tube that collects CO2 goes. I know one end is placed inside of the cap of my bottle, but how does the other end attatch to effect the graduated cylinder?
Thanks

[donnahardy2]

Hi,

Good question. This project idea would be better with a photograph. Here is what you need to do before you start the experiment; the glass cylinder or bottle needs to be completely submerged in water.

a. Fill the graduated cylinder with water.
i. If your tub is big enough, fill the graduated cylinder by tipping it on its side inside the tub. Allow any bubbles to escape by tilting the cylinder up slightly, while keeping it under water. Keeping the opening of the cylinder under water, turn it upside down and attach it to the side of the tub with packing tape.
ii. If your tub is not big enough, fill the graduated cylinder completely and cover the top tightly with plastic wrap. Quickly invert the cylinder and place the opening in the tub, beneath the surface of the water. Remove the plastic wrap. Attach the cylinder to the side of the tub with packing tape.
b. The graduated cylinder should now be upside down, full of water and with its opening under the surface of the water in the tub. It is ready to trap CO2

You have sealed one end of the tubing in the fermentation container, so any carbon dioxide produced can only go into the tubing. The other end of the tubing needs to be inserted in the inverted water-filled graduated cylinder and secured into place so the open end of the tubing is inside of the glass cylinder. You will have to support the cylinder with the tubing so it doesn't tip over during the experiment. As carbon dioxide is produced, the trapped water will gradually be replaced with air.

Does this help?

Donna Hardy