Bread Production and the Role of Yeast

Question 1

what is anaerobic respiration used for in yeast?

Answer 1

during beer brewing and bread making

Question 2

what is the anaerobic equation in yeast?

Answer 2

glucose -> ethanol + carbon dioxide

Question 3

is ethanol found in alcoholic drinks like beer and wine?

Answer 3

yes

Question 4

how does bread rise?

Answer 4

bubbles of carbon dioxide gas expand the dough

Question 5

is ethanol present in bread after cooking has finished?

Answer 5

no - the high temperatures used means the ethanol evaporates

Question 6

in the presence of carbon dioxide, what colour does limewater turn?

Answer 6

cloudy white (milky)

Question 7

in the presence of carbon dioxide, what colour does hydrogen carbonate turn?

Answer 7

from orange to yellow

Question 8

method to investigate anaerobic respiration by studying production of carbon dioxide under different conditions?

Answer 8

1. dissolve sugar in previously boiled water
2. add yeast and mix to form a suspension, and pour into a boiling tube
3. add a layer of vegetable oil
4. connect to a delivery tube to a second boiling tube, this time containing limewater or hydrogen carbonate indicator

Question 9

why is vegetable oil added in the production of carbon dioxide experiment?

Answer 9

to prevent oxygen from entering the mixture, while allowing carbon dioxide to escape - this ensures it’s anaerobic respiration taking place

Question 10

how can you measure the production of carbon dioxide from the experiment?

Answer 10

it usually takes an hour or so for fermentation to be visible - the number of bubbles over a set time can be counted, or the appearance of the indicator can be compared to a control containing boiled (dead) yeast

Question 11

what conditions can be investigated in the production of carbon dioxide in yeast?

Answer 11

• temperature
• concentration of sugar
• type of sugar