Required Practical 9 Flashcards
(27 cards)
What is the aim of Required Practical 9?
Investigate the effect of temperature on yeast respiration.
What organism is used in this experiment?
Yeast.
How does yeast respire?
Aerobically and anaerobically.
What is used to measure respiration?
Methylene blue dye.
What happens to methylene blue during respiration?
It changes from blue to colourless.
What equipment is needed?
Yeast solution, water bath, thermometer, test tubes, timer.
What is the variable in the experiment?
Temperature.
What temperature should the water bath be set to initially?
35°C.
How much yeast solution is used in each test tube?
5 cm³.
How long should the test tubes equilibrate in the water bath?
10 minutes.
What is added to the test tubes after equilibration?
2 cm³ of methylene blue.
How long should the test tubes be shaken after adding methylene blue?
10 seconds.
How is the rate of respiration measured?
By how long it takes for methylene blue to turn colourless.
What temperatures should the experiment be repeated at?
40°C, 50°C, 60°C, 70°C.
What should you calculate after the experiment?
The mean rate of respiration for each temperature.
Why is the solution buffered?
To maintain a constant pH.
What is the risk with DCPIP?
It is an irritant and can stain.
How do you handle DCPIP safely?
Wear eye protection and wash off with cold water if in contact with skin or eyes.
What risk does broken glass pose?
Cuts.
How should broken glass be handled?
Handle with care, keep away from edges.
What is the risk of hot liquids?
Scalding.
How do you safely handle hot liquids?
Use tongs and wear eye protection.
What should you do if burned?
Run under cold water and seek medical help.
What should be graphed in the experiment?
Rate of respiration vs. temperature.
