The relationship between CO2 gas produced to sugarconsumed is shown below.
m = n / 2s
where m is the number of moles of sugar consumed,n is the number of moles of CO2 produced, ands is the number of simple sugars in that sugar.
This means that for:
a monosaccharide, 2 CO2 molecules are produced permolecule of sugar
a disaccharide, 4 CO2 molecules are produced permolecule of sugar
a trisaccharide, 6 CO2 molecules are produced permolecule of sugar
Calculating the Rate of Respiration
First, use the Ideal Gas Law to convert the volume of gas tomolecules. This is measured in moles, not the number of individualmolecules. The Ideal Gas Law relates the moles of CO2gas molecules to its volume as shown in the equation below.
PV = nRT
where P is the atmospheric pressure in the lab,V is the volume in liters, n is the number ofmoles of CO2, R is the gas constant 0.082L-atm/mole-Kelvin, and T is the temperature in Kelvin.
Next, convert the moles of CO2 molecules produced tothe moles of sugar consumed using the equation shown below.
m = n / 2s
Finally, combine several calculations to convert the results tomilligrams of sugar fermented per minute:
convert from moles to grams
convert from grams to milligrams
divide by the length of respiration
The formula is below.
f = 1000mw / t
where f is the mg of sugar fermented per minute,m is the number of moles of sugar consumed, w isthe molecular weight of the sugar in g/mole, and t is therespiration time in minutes.
For example, if 1 L of CO2 is collected when yeast isincubated with maltose for 5 minutes and the final temperature ofthe flask is 294.5 K, the milligrams of sugar fermented per minuteare calculated as follows:
moles of CO2 = (1 atm × 1 L CO2) ÷ (0.082L-atm/mole-Kelvin × 294.5 K)
moles of CO2 = 0.041 moles
moles of maltose consumed = 0.04141 moles ofCO2produced ÷ (2 × 2 simple sugars in maltose)
moles of maltose consumed = 0.01035 moles
mg of maltose per minute = (0.01035 moles maltose) × (MW ofmaltose) × (1000 mg/g) ÷ (5 minutes) Â
mg of maltose per minute = 708.6 mg/min
| SugarInformation Table |
|---|
| Sugar | Sugar Type | Molecular weight |
|---|
| glucose | mono | 180.2 g/mole |
| fructose | mono | 180.2 g/mole |
| maltose | di | 342.3 g/mole |
| maltotriose | tri | 504.4 g/mole |
For each of the sugars fermented by yeast, fill in the chartbelow to determine the volume of CO2 production.
Results Table(my answers)
Sugar | Initial Gas
Volume at t = 0 minutes (mL) | Final Gas
Volume at t = 1 minutes (mL) | Volume of Co2 Produced
Final - Initial (mL) |
glucose | 0.0 ml | 4.3 ml | 4.3 ml |
fructose | 0.0 ml | 1.3 ml | 1.3 ml |
maltose | 0.0 ml | 5.1 ml | 5.1 ml |
maltotriose | 0.0 ml | 1.0 ml | 1.0 ml |
For each of the sugars fermented by yeast, fill in the chartbelow to determine the mg of sugar consumed per minute duringfermentation.
Calculations Table
Sugar | MW (g/mole) | Moles of CO2 produced | Moles of Sugar consumed | mg of sugar/min |
fructose | | | | |
maltose | | | | |
maltotriose | | | | |
My answers
Glucose temp 299.0k after 1 minute and 4.3ml in syringe
fructose temp 296.0k after 1 minute 1.3ml of gas in thesyringe
maltose temp 300.0k after 1 minute 5.1 ml
maltotriose temp 295.6k after 1 minute 1.0 ml
