Fermentation by Yeast

Question 1

What is the function of cellular respiration?

Answer 1

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

Question 2

What is ATP?

Answer 2

A molecule that is a source of energy for cells

Question 3

What is oxidation?

Answer 3

The loss of electrons

Question 4

What is reduction?

Answer 4

The gaining of electrons

Question 5

Which molecule is oxidized during cellular respiration? Which is reduced?

Answer 5

glucose is oxidized

O2 is reduced

Question 6

What is the overall reaction for cellular respiration?

Answer 6

C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + Energy (ATP & heat)

Question 7

What is the role of oxygen in cellular respiration?

Answer 7

Oxygen acts as the final electron acceptor for the electrons removed from glucose

Question 8

What is the energy yield of cellular respiration per molecule of glucose?

Answer 8

~32 ATP

Question 9

What happens if oxygen is not present?

Answer 9

Fermentation

Question 10

Will ATP production shut down if oxygen is not present?

Answer 10

No, instead of aerobic cellular respiration, fermentation will occur

Question 11

What occurs during glycolysis?

Answer 11

the 6C glucose molecule is broken down into two 3C molecules of PYRUVATE, producing 2 molecules of ATP

Question 12

What is the energy yield of glycolysis?

Answer 12

2 ATP

Question 13

Does glycolysis require oxygen to occur?

Answer 13

No

Question 14

What are the products of glycolysis?

Answer 14

2 molecules of the 3C pyruvate

2 ATP

Question 15

T or F: the additional chemical reactions of fermentation produce more ATP

Answer 15

False.

They do not produce more ATP, they only function to allow glycolysis to continue

Question 16

What is the purpose of the rest of the chemical reactions of fermentation?

Answer 16

They allow glycolysis to continue

Question 17

What is reduced during cellular respiration?

Answer 17

Oxygen is reduced to water

Question 18

How are the electrons transferred from glucose to oxygen?

Answer 18

1. electrons are oxidized from glucose

2. electrons move ‘down’ an electron transport chain where they release energy that is collected to produce ATP

Question 19

In fermentation, what molecules can accept the electrons removed from glucose?

Answer 19

Either pyruvate or acetaldehyde

Question 20

What is the product of lactic acid fermentation?

Answer 20

lactate

Question 21

What is the product of alcohol fermentation?

Answer 21

ethanol

Question 22

Is there an electron transport chain involved in fermentation?

Answer 22

No and therefore no more ATP can be produced

Question 23

In this experiment, how is the rate of fermentation measured?

Answer 23

By assaying carbon dioxide production for different concentrations of sucrose

Question 24

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?

Answer 24

10

Question 25

Muscle cells in oxygen deprivation convert pyruvate to ____, whereas microorganisms such as yeast convert pyruvate to ____

Answer 25

lactic acid; ethanol

Question 26

What is the source of electrons in cellular respiration?

Answer 26

glucose

Question 27

What is the purpose of this experiment?

Answer 27

to determine the effects of sucrose/sugar concentration on the rate of fermentation by yeast by measuring the production of carbon dioxide

Question 28

In this experiment, the ___ tube value was subtracted at 15 minutes from each ___ tube value at 15 minutes to get the adjusted froth height

Answer 28

control; experimental

Question 29

Why does the sucrose concentration need to be adjusted?

Answer 29

because the yeast stock solution will be added to each sucrose solution, changing the concentration

Question 30

in this lab you will be calculating the mean, variance, standard deviation, and ___ confidence intervals

Answer 30

95%

Question 31

What species was used for this experiment? Give both the common and latin names

Answer 31

Baker's yeast Saccharomyces cerevisiae

Question 32

What is baker's yeast?

Answer 32

a species of unicellular fungus that is essential to the food and beverage industries

Question 33

Why was baker's yeast chosen for this experiment?

Answer 33

Because it has evolved to digest naturally occurring sugars such as sucrose

Question 34

What is sucrose?

Answer 34

A disaccharide composed of glucose and fructose monosaccharides that is naturally produced by plants and some photosynthetic prokaryotes and protists

Question 35

Define fermentation

Answer 35

a catabolic pathway that occurs without the presence of oxygen to break down glucose/sugars into specific products

Question 36

By what method are the 2 molecules of ATP produced during glycolysis?

Answer 36

substrate-level phosphorylation

Question 37

During fermentation, what acts as the electron carrier to remove electrons from glucose?

Answer 37

Coenzyme NAD+

Question 38

In lactic acid fermentation, which molecule is the final electron acceptor?

Answer 38

Pyruvate

Question 39

Briefly describe the processes of lactic acid fermentation

Answer 39

After glycolysis has converted glucose into pyruvate, the pyruvate is reduced by electrons transferred by NADH to produce lactate in one step

Question 40

Does lactic acid fermentation release CO2?

Answer 40

No

Question 41

How does lactic acid fermentation regenerate the supply of NAD+ to sustain glycolysis?

Answer 41

NADH is oxidized to NAD+ when it transfers the electrons to pyruvate

Question 42

What form of fermentation does baker's yeast conduct?

Answer 42

Alcohol

Question 43

How many steps occur in alcohol fermentation?

Answer 43

2

Question 44

Briefly describe the processes of alcohol fermentation

Answer 44

After glycolysis has converted glucose into pyruvate, 1. the pyruvate is converted into the 2C acetaldehyde by accepting electrons oxidized from glucose - this step releases CO2 2. acetaldehyde is reduced to form the product (ethanol) when NADH transfers an electron and oxidizes to NAD+

Question 45

How does alcohol fermentation regenerate the supply of NAD+ to sustain glycolysis?

Answer 45

NADH oxidizes to NAD+ when it gives acetaldehyde the electrons

Question 46

What is the final electron acceptor in alcohol fermentation?

Answer 46

acetaldehyde

Question 47

What does the release of CO2 from alcohol fermentation produce?

Answer 47

frothy bubbles

Question 48

What will be measured in this experiment to assay the rate of alcohol fermentation by baker's yeast?

Answer 48

the height of the frothy bubbles released by CO2

Question 49

what were the 5 concentrations of sucrose used in this experiment?

Answer 49

0.1 M, 0.2 M, 0.4 M, 0.8 M, and 1.6 M

Question 50

Which hypothesis was rejected based on the results of this experiment?

Answer 50

The null hypothesis

Question 51

What was the supported hypothesis?

Answer 51

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.