Fermentation by Yeast Flashcards
What is the function of cellular respiration?
To extract energy from glucose and other organic compounds and transfer it to ATP
What is ATP?
A molecule that is a source of energy for cells
What is oxidation?
The loss of electrons
What is reduction?
The gaining of electrons
Which molecule is oxidized during cellular respiration? Which is reduced?
glucose is oxidized
O2 is reduced
What is the overall reaction for cellular respiration?
C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + Energy (ATP & heat)
What is the role of oxygen in cellular respiration?
Oxygen acts as the final electron acceptor for the electrons removed from glucose
What is the energy yield of cellular respiration per molecule of glucose?
~32 ATP
What happens if oxygen is not present?
Fermentation
Will ATP production shut down if oxygen is not present?
No, instead of aerobic cellular respiration, fermentation will occur
What occurs during glycolysis?
the 6C glucose molecule is broken down into two 3C molecules of PYRUVATE, producing 2 molecules of ATP
What is the energy yield of glycolysis?
2 ATP
Does glycolysis require oxygen to occur?
No
What are the products of glycolysis?
2 molecules of the 3C pyruvate
2 ATP
T or F: the additional chemical reactions of fermentation produce more ATP
False.
They do not produce more ATP, they only function to allow glycolysis to continue
What is the purpose of the rest of the chemical reactions of fermentation?
They allow glycolysis to continue
What is reduced during cellular respiration?
Oxygen is reduced to water
How are the electrons transferred from glucose to oxygen?
- electrons are oxidized from glucose
2. electrons move ‘down’ an electron transport chain where they release energy that is collected to produce ATP
In fermentation, what molecules can accept the electrons removed from glucose?
Either pyruvate or acetaldehyde
What is the product of lactic acid fermentation?
lactate
What is the product of alcohol fermentation?
ethanol
Is there an electron transport chain involved in fermentation?
No and therefore no more ATP can be produced
In this experiment, how is the rate of fermentation measured?
By assaying carbon dioxide production for different concentrations of sucrose
Suppose a yeast cell uses 5 moles of glucose for energy production in the absence of oxygen. What will be the maximum net yield of ATP in moles?
10
Muscle cells in oxygen deprivation convert pyruvate to ____, whereas microorganisms such as yeast convert pyruvate to ____
lactic acid; ethanol
What is the source of electrons in cellular respiration?
glucose
What is the purpose of this experiment?
to determine the effects of sucrose/sugar concentration on the rate of fermentation by yeast by measuring the production of carbon dioxide
In this experiment, the ___ tube value was subtracted at 15 minutes from each ___ tube value at 15 minutes to get the adjusted froth height
control; experimental
Why does the sucrose concentration need to be adjusted?
because the yeast stock solution will be added to each sucrose solution, changing the concentration
in this lab you will be calculating the mean, variance, standard deviation, and ___ confidence intervals
95%
What species was used for this experiment? Give both the common and latin names
Baker’s yeast
Saccharomyces cerevisiae
What is baker’s yeast?
a species of unicellular fungus that is essential to the food and beverage industries
Why was baker’s yeast chosen for this experiment?
Because it has evolved to digest naturally occurring sugars such as sucrose
What is sucrose?
A disaccharide composed of glucose and fructose monosaccharides that is naturally produced by plants and some photosynthetic prokaryotes and protists
Define fermentation
a catabolic pathway that occurs without the presence of oxygen to break down glucose/sugars into specific products
By what method are the 2 molecules of ATP produced during glycolysis?
substrate-level phosphorylation
During fermentation, what acts as the electron carrier to remove electrons from glucose?
Coenzyme NAD+
In lactic acid fermentation, which molecule is the final electron acceptor?
Pyruvate
Briefly describe the processes of lactic acid fermentation
After glycolysis has converted glucose into pyruvate, the pyruvate is reduced by electrons transferred by NADH to produce lactate in one step
Does lactic acid fermentation release CO2?
No
How does lactic acid fermentation regenerate the supply of NAD+ to sustain glycolysis?
NADH is oxidized to NAD+ when it transfers the electrons to pyruvate
What form of fermentation does baker’s yeast conduct?
Alcohol
How many steps occur in alcohol fermentation?
2
Briefly describe the processes of alcohol fermentation
After glycolysis has converted glucose into pyruvate,
- the pyruvate is converted into the 2C acetaldehyde by accepting electrons oxidized from glucose
- this step releases CO2 - acetaldehyde is reduced to form the product (ethanol) when NADH transfers an electron and oxidizes to NAD+
How does alcohol fermentation regenerate the supply of NAD+ to sustain glycolysis?
NADH oxidizes to NAD+ when it gives acetaldehyde the electrons
What is the final electron acceptor in alcohol fermentation?
acetaldehyde
What does the release of CO2 from alcohol fermentation produce?
frothy bubbles
What will be measured in this experiment to assay the rate of alcohol fermentation by baker’s yeast?
the height of the frothy bubbles released by CO2
what were the 5 concentrations of sucrose used in this experiment?
0.1 M, 0.2 M, 0.4 M, 0.8 M, and 1.6 M
Which hypothesis was rejected based on the results of this experiment?
The null hypothesis
What was the supported hypothesis?
The alternative: a change in sucrose concentration (M) will have an effect on the production of carbon dioxide (mm) by baker’s yeast, Saccharomyces cerevisiae.
