Fermentation

Question 1

what is the function of cellular respiration? how is this done? what is the energy yield of cellular respiration per molecule of glucose?

Answer 1

to extract energy from glucose (and other organic compounds) and transfer it to ATP

• done through a complex set of reactions as electrons are removed from glucose and some of their energy is transferred to ATP
• 32 ATP per molecule

Question 2

what is the loss of electrons called? what is the gain of electrons called?

Answer 2

• oxidation

- reduction

Question 3

why does O2 occur on the left side of the cellular respiration formula?

Answer 3

because the complete oxidation of glucose to CO2 and H2O only occur ifs oxygen is present to act as the final acceptor of the electrons removed from glucose

Question 4

what happens if oxygen is not present?

Answer 4

ATP production does not shut down –> instead proceeds through process of fermentation

Question 5

what is the step that occurs in both cellular respiration and fermentation? does it require oxygen? what happens during these series of reaction? what is the direct energy yeild of this?

Answer 5

• glycolysis
• no oxygen required
• a 6-carbon glucose is broken down to 2 3-carbon molecules of pyruvate
• direct energy yield of 2 ATP

Question 6

after glycolysis, does fermentation produce more ATP?what do additional chemical reactions of fermentation accomplish? why is ATP not produced?

Answer 6

• no more ATP is produced
• additional reactions simply allow glycolysis to continue
• ATP not produced because electrons do not move down electron transport chain and therefore do not build a gradient

Question 7

what molecule acts as a final electron acceptor in cellular respiration? what is it reduced to?

Answer 7

• oxygen

- reduced to water

Question 8

what molecules act as a final electron acceptor in fermentation? what are they reduced to?

Answer 8

• pyruvate –> reduced to lactic acid

- acetaldehyde –> reduced to ethanol

Question 9

during fermentation, what do most animal cells and microorganisms produce? what do most plants cells and yeast produce, what is the byproduct?

Answer 9

• lactic acid
• ethanol
• byproduct is CO2

Question 10

what organism was used in this lab, what is its scientific name? what does the product and byproduct do?

Answer 10

• bakers yeast –> Saccharomyces cerevisiae
• the product alcohol, does nothing, simply evaporates
• the byproduct CO2 acts as a leavening or rising agent (makes bubbles)

Question 11

what was the purpose of this lab?

Answer 11

to measure the rate of fermentation for different concentrations of sucrose through carbon dioxide production, which could be measured by froth height

Question 12

what was the null hypothesis for the experiment? what was the alternative hypothesis?

Answer 12

The concentration of sucrose (M) has no effect on the rate of fermentation (as measured by froth height in mm) by Baker’s yeast (Saccharomyces cerevisiae).
-The concentration of sucrose (M) has an effect on the rate of fermentation (as measured by froth height in mm) by Baker’s yeast (Saccharomyces cerevisiae).