RP 9 Flashcards
Why do you leave the tubes in the water bath for 5 minutes
To allow for the yeast and Glucose mixture to reach the required temperatures
What is required practical 9
Investigation into the effect of a named variable (temperature) on the rate of respiration of yeast cultures
How does yeast respire
Aerobically
Anaerobically
What is methylene blue
An electron acceptor
Accepts electrons and changes from blue to colourless
How do you monitor the temperature of the water bath
Use a thermometer
Measure the temperature at regulat intervals (e.g every minute)
Adding hot or cold water as necessary
To maintain the temperature at …
Describe the control experiment and why it is important
Methylene blue and glucose or methylene blue, glucose and boiled yeast
To show the glucose wasn’t responsible for the colour change from blue to colourless and that it was caused by yeast respiration
Why don’t you shake the tubes/why do you use a bung
It would have caused the methylene blue to go blue again
Mixing with air/oxygen
Oxidises methylene blue
And forces it to give up its electrons
Respiration by yeast causes methylene blue to go colourless. How.
Methylene blue accepts the electrons
Released from coenzymes/glucose
Why does a higher temperature cause a faster colour change
Increased kinetic energy
More collisions per second
More enzyme substrate complexes form per second
Faster rate of respiration means more electrons released per second
More electrons for methylene blue to accept per second
Less time for decolourisation of methylene blue
Why is it important to leave apparatus for an hour if investigating anaerobic respiration with yeast
So all the oxygen is removed
Either absorbed by oxygen absorber or respired
Why do many cells die during the death phase
No glucose
Increased ethanol hence toxins
