Fermentation and Respiration

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Joined: Tue Feb 24, 2009 9:46 am

Fermentation and Respiration

Post by bottleofboos » Tue Feb 24, 2009 10:22 am

I have some questions that I need help with:

1. How will increasing the number of yeast cells affect the rate of ATP production by cells if the sugar concentration in the experiment is held constant?
I think increasing the number of yeast cells will increase the rate of ATP production. There is a greater number of yeast cells to consume the sugar, and the sugar concentration is held constant which means there is enough sugar to keep the ATP production going.

2. How will substituting galactose for glucose affect the rate of ATP production by the cells?
Even though glucose and galactose have the same molecular formula, the difference between these two sugars is the fourth carbon chain. Glucose has it as H-C-OH, but galactose is the opposite of this. I believe galactose is not usable in cellular respiration. If galactose was substituted, I believe that the rate will lower and will eventually stop when it runs out of glucose. Why is galactose not usable in cellular respiration?

3. Will the yeast cells or the corn seedling have a higher metabolic rate when compared on a mass specific basis? (comparing fully hydrated seeds to dry yeast)
Aerobic respiration would always provide a greater yield in ATP compared to alcohol fermentation. Using this information, I know the corn seedling will have a higher metabolic rate. But how would I be able to prove this?

Thanks for any help you can give me :mrgreen:

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Post by RGoodman » Tue Feb 24, 2009 8:46 pm

hi there, hope this helps.

1. i believe there will be a boom and bust situation here. if you increase the number of yeast cells the production of ATP will increse for a while but it will then fall again. this is due to the fact that the increased number of cells is using the glucose that much quicker, but they are also increasing the toxin levels within the solution. as a by product of ATP production the yeast cells create toxins which will eventaully kill them rendering them useless.

2. i think you have mis understood the question here. it is saying what would happen if galactose is changed for glucose. the resulting soltuion would have an incresed level of ATP production.

3. resperation has 3 main stages. glycolysis, the Krebs Cycle and the Electron Transfer Chain. Glycolysis occurs in both aerobic and anerobic respiration creating only 2 ATP molecules for every 1 glucose. the Krebs Cycle and the Electron transport chain only work when there is suphicant oxygen to drive the reaction frward. therefore only working during aerobic respiration. the krebs cycle creates 36 ATP molecules for every 1 glucose. with this in mind corn seedlings will give a higher yield that that og dry, or alchol fermination.

hope this helps, if you want any more info please get back to me.

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Post by MrMistery » Sun Mar 01, 2009 2:56 pm

2. cells can utilize galactose, although not in cellular respiration directly. there are special enzymes that act on each of the alternative sugars to convert them into glycolysis intermediates

3. it really depends if you are measuring the ATP production of yeast in the presence or absence of oxygen. Yeast carries out aerobic respiration if there is oxygen present.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter