practical: investigate the role of anaerobic respiration by yeast in different conditions Flashcards
5.6
what is anaerobic respiration in yeast cells called?
fermentation
what is one way to investigate anaerobic respiration?
study the production of CO2 under different conditions
what happens to limewater in the presence of carbon dioxide?
limewater turns cloudy whitre (milky)
what happens to hydrogen carbonate indicator in the presence of CO2?
changes from orange to yellow
what apparatus will be needed for this experiment?
boiling tubes
capillary tubes
bungs
yeast
sugar solution
oil
stopwatch
water bath
limewater
how to conduct this experiment?
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 a delivery tube to a second boiling tube, this time containing limewater or hydrogen carbonate indicator
what does the layer of vegetable oil prevent?
prevents oxygen entering the mixture, while allowing carbon dioxide to escape
this ensures anaerobic respiration is taking place
how long does it take for fermentation to be visible?
an hour or so
what can you count?
the number of bubbles over a set time
what can the appearance of the indicator be compared to?
a control containing boiled (dead) yeast
what would CORMS be for this investigation?
C- changing the temperature in each repeat
O- the type (species) of yeast we are using must be the same
R- repeat the experiment several times at each temperature to ensure our results are reliable
M1- measure the number of bubbles produced
M2- in a set period of time e.g. 2 minutes
S- control the concentration, volume and pH of the sugar solution as well as the mass of the yeast added
