[lfcs123]

Hi, I need to write up the experiment, and I am struggling with the calculations.

I have got 3g/100 mL suspension of yeast in 20mM phosphate buffer pH 7.5.

I made up solution of total volume 4mL:

- 2.9 mL potassium phosphte buffer ph 7.5
- 1 mL of yeast suspension
- 0.1 mL 50 mM sugar

I had to measure the rate of oxygen consumption by noting the oxygen concentration at time 0 and 60 minute, this is my data;

Oxygen electrode measurements
                 
                  µmol O2               µmol O2
Time (min)            0                     60
D-glucose            1.9                   1.1
L-glucose             1.9                   1.8
2 Deoxy-D-glucose 1.6                  1.7
water                   0.3                  0.5

i have question;


The above is the amount in mol present in that suspension, how can i calculate the rate of oxygen uptake or consumption.

how do I know if the substrates are respired aerobically

can someone point an article where the above experiment is used.

thanks

[Arkcon]

Hi, I need to write up the experiment, and I am struggling with the calculations.

I have got 3g/100 mL suspension of yeast in 20mM phosphate buffer pH 7.5.

I made up solution of total volume 4mL:

- 2.9 mL potassium phosphte buffer ph 7.5
- 1 mL of yeast suspension
- 0.1 mL 50 mM sugar

OK.  The setup is easy to understand.

I had to measure the rate of oxygen consumption by noting the oxygen concentration at time 0 and 60 minute, this is my data;

OK.  And that's what you had to do.  Got it.

Oxygen electrode measurements
                 
                  µmol O2               µmol O2
Time (min)            0                     60
D-glucose            1.9                   1.1
L-glucose             1.9                   1.8
2 Deoxy-D-glucose 1.6                  1.7
water                   0.3                  0.5

I don't see an oxygen measurement.  You said that's what you did.  Typo?  Or do you mean something else?

i have question;


The above is the amount in mol present in that suspension, how can i calculate the rate of oxygen uptake or consumption.

Maybe you can calculate it from your measurements, using a chemical reaction.  You can find that ion a textbook, or the lab write-up.

how do I know if the substrates are respired aerobically

Hmm...the devil is going to be in the details on this one.  What did you do to insure the reaction was aerobic.  What could have stopped it from being aerobic.

can someone point an article where the above experiment is used.

Probably not.  Fermenting sugar with yeast was first done experimentally in human prehistory.  Maybe new strains are tested in this manner, say for a new strain of wine or beer yeast.  But I doubt a journal will publish an undergraduate experiment.  We're kinda done with publishing this sort of thing.  Maybe L. Pasteur's notebook has these sorts of measurements, but wherever they're kept, you're not likely to get to touch them.

thanks

Lets start with what you have, and see where it will go.

[Babcock_Hall]

What are your expectations with respect to the experiment with L-glucose?
EDT
With respect to the rate of oxygen consumption, you have a starting concentration, a final concentration, and a time.  IMO this is all you need.

[Babcock_Hall]

@OP, What is the stereochemical relationship between D-glucose and L-glucose?  BTW, this is a smallish point, but it would be helpful to know how large the error is in the measurement of oxygen.

[Babcock_Hall]

@OP  On the basis of your data, was any oxygen consumed in the presence of 2-deoxyglucose?  This compound has been studied for many years for its effect on glycolysis.

[lfcs123]

hi, can someone suggest a recent article to read as I have been told to compare D-glucose, L-glucose and 2-deoxy-d-glucose as substrates for aerobic respiration by yeast.

[Babcock_Hall]

ifcs123,

My advice is to start by calculating the rate of oxygen consumption in micro moles per hour (or micro moles per minute if you prefer), based upon your data in the opening post.  Then take a shot at the questions I posed above, which were intended to point you in the right direction.  You already have all of the data you need.

[lfcs123]

ifcs123,

My advice is to start by calculating the rate of oxygen consumption in micro moles per hour (or micro moles per minute if you prefer), based upon your data in the opening post.  Then take a shot at the questions I posed above, which were intended to point you in the right direction.  You already have all of the data you need.

hi, i have been recently told by my teacher that I did not need to work out the rate of oxygen consumption. I just needed to know the differences between the start and end point of the substrates to identify if the oxygen has been used by comparing it with the error margin of 0.2 in water.

can you please suggest an article that could explain the role of d-glucose, l-glucose and 2-dseoxy-d-glucose in yeast metabolism.

As I need to explain why L-glucose did not uptake and many more questions.

[Babcock_Hall]

Now that we know what the size of the error is, we can say once and for all which compounds brought about oxygen consumption and which did not.  You don't need an article; the answers are in your data.  Besides, there might not be anything on L-glucose and yeast, although you could try a search using PubMed.  Chapter 14 in Nelson and Cox's textbook Principles of Biochemistry would be a resource to use for D-glucose.

Was there significant (beyond the margin of error) oxygen consumption when L-glucose was used?  What is the stereochemical relationship between L-glucose and D-glucose?  Are proteins chiral or achiral?  If you can answer these two questions, you are well on your way.