# I NEED HELP ON MY BIOLOGY 1 HOMEWORK!!!!!!!!



## CookinBlondie (Dec 1, 2004)

Ok, here's the deal. I am on my last questions in bio 1, and this one I thought you all could help me on. Here it is:

Bread rises as a result of yeast fermentation. How might fermentation cause bread to rise?  Why is sugar often added to bread dough?

So, can you help me?  I would really appreciate it. Thanks!

_CookinBlondie*_


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## Lifter (Dec 1, 2004)

I'm not the best one to answer this CB, but yeast is in fact a living organism that needs moisture, heat and "food" to "prosper"...

In this case, you have provided the moisture and the temperature in your bread dough medium, so your addition of sugar allows for the little yeast varmints to eat.

As they eat and grow, they give off oxygen by serving them selves the "hydro carbons" pulled out of the water/sugar mix, which of course, causes the "bubbles" that are formed in the interior of the bread loaf...

As the loaf/dough is being "pumped full of air" by this action, it is caused to "rise" as the dough medium does not allow the oxygen gas to escape....

When you bake the dough, the heat causes the gasses to further expand (simple physics, that!) until the bread is fully formed and dried, being somewhat rigid (think "crust") and you, of course, remove it from the oven...

I'd wait for a couple other respondents to clock in on this one, to check out my exact chemistry...

Lifter


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## CookinBlondie (Dec 1, 2004)

Okay, odviously this isn't getting anywhere. I just thought you all would know. I need to go to bed soon, so do you guys have ANY idea what this could be about? Do not worry about cheating. I never cheat, and I have been given permission by my bio teacher to use any resource i can find to help me. Please, any idea will be of value to me. Thanks.

_CookinBlondie*_

EDIT: SORRY, THERE WERE NO OTHER POSTS WHEN I STARTED THIS ONE. THANKS LIFTER, YOU LIFTED MY HOMEWORK SPIRITS.  :roll:


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## DampCharcoal (Dec 1, 2004)

This may sound crude but to quote a buddy of mine who was a wine steward, "Yeast feeds on sugar, farts CO2 and pisses alcohol."


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## debthecook (Dec 1, 2004)

Maybe Fleischmann's can help
http://www.breadworld.com/sciencehistory/science.asp


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## Psiguyy (Dec 1, 2004)

CookinBlondie said:
			
		

> Ok, here's the deal. I am on my last questions in bio 1, and this one I thought you all could help me on. Here it is:
> 
> Bread rises as a result of yeast fermentation. How might fermentation cause bread to rise?  Why is sugar often added to bread dough?
> 
> ...



A byproduct of fermentation is CO2 (carbon dioxide), a clear and odorless gas.  The gas is trapped by the elastic, almost rubbery, dough causing the dough to rise.  Baking the dough causes the CO2 to heat up and expand further, causing the dough to rise even more.  

Sugar is added to provide food for the yeast, but in most cases, sugar is added for the sweet flavor.  The sugar is not really required for the yeast to grow.  Millions of loaves of bread are baked every day that only has flour, yeast, and water in the dough.


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## CookinBlondie (Dec 1, 2004)

Psiguyy said:
			
		

> CookinBlondie said:
> 
> 
> 
> ...



Thanks all of you! Free hugs now available! So, when you do add sugar, what exactly happens? What exactly do you mean by "helps the yeast"?
_
CookinBlondie*_


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## debthecook (Dec 1, 2004)

From the Food Network:

All baker's yeast should be given a test called proofing to make sure it's still alive. To proof yeast, dissolve it in warm water and add a pinch of sugar. Set the mixture aside in a warm place for 5 to 10 minutes. If it begins to swell and foam, the yeast is alive, active and capable of leavening bread.


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## CookinBlondie (Dec 1, 2004)

Okay guys, here's my answer:

A byproduct of fermentation is CO2. This gas is trapped by the dough, causing it to rise. Baking the dough causes the carbon dioxide to heat up and expand further, causing even more rising. Yeast, being a living organism, feeds off of the sugar, and is able to produce more CO2, and alcohol.

Is it good? Hope so. Well thanks for your help! I will tell you how I did after I get it graded tommarow. Thanks again! You guys are the best!

_CookinBlondie*_


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## debthecook (Dec 1, 2004)

Whats that about the alcohol???, I thought your questions were about yeast in breadmaking.


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## -DEADLY SUSHI- (Dec 1, 2004)

Im glad I could help!  :roll:


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## ronjohn55 (Dec 2, 2004)

debthecook said:
			
		

> Whats that about the alcohol???, I thought your questions were about yeast in breadmaking.



Yeast, all yeast, do indeed feed on sugar. (Some specialized strains can feed on more complex forms of sugar) There are other nutrient requirements as well, but unless you need a ton of sugar converted, it's not an issue. 

As the yeasts eat the sugar, the do indeed give of CO2 and alcohol. If you bake it, the trace alcohol goes away. (Lifter's explanation was spot on, except that it's CO2 and not O2)

HOWEVER, add it to beer/wine, and you have the mechanism by which fermentation is achieved. Brewers (and to a lesser extent, vinters) have to take very good care of their yeasts, or any number of bad things will happen (including unsellable beer - bad for business). 

As an aside, if you were to put a pound of sugar in a gallon of water, you'd get a alcoholic beverage of about 4-4.5 percent alcohol by volume.  Actively fermenting yeast are also how beer and champagne first got their bubbles. 

John

Sheesh! Do I sound like I need to get out of the lab more often, or what?


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## debthecook (Dec 2, 2004)

I know that the trace elements of alcohol are burned off in baking. I was just concerned that his last sentence bringing up the alcohol may not be in the right place (I have a BA in English, I should get out of the english texts too) or appropriate for this paragraph.


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## ronjohn55 (Dec 2, 2004)

Ahhh....

Proper english and grammar - NOT my strongest point   

John


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## debthecook (Dec 2, 2004)

Neither is my science.


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## CookinBlondie (Dec 2, 2004)

THANKS GUYS!!!!! Well, I got full points on that problem you all helped me on, and I know more about fermentation now. 

The entire fermentation process starts with glucose (sugar).  The sugar goes through glycolysis, and is converted to pyruvate.  With out the presence of oxygen, the pyruvate goes through fermentatioin, rather than oxidative respiration if the oxygen would have been present.  Once fermentation is complete, the end products are carbon dioxide and ethyl alcohol.  That's where the yeast comes in.  The alcohol and CO2 help the dough rise.

I couldn't have done it without your help.  Thanks again!

_CookinBlondie*_


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## Lifter (Dec 3, 2004)

(SIGH!)

Another C- in science, after I blew the call on Oxygen vs CO2...

It gets "scarey" that we are teaching CB about "fermentation" at this early point of her innocent life...

LOL!

Lifter


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