Practical 3 - Investigation into factors affecting respiration in yeast Flashcards
What is yeast?
A unicellular fungus
What does yet produce when repairing?
CO2
What does yeast do to release CO2?
Respire
What is respiration controlled by?
Enzymes
How can we measure the rate of respiration of yeast in this practical?
The rate of formation of CO2 can be used
What does this practical investigate?
Factors affecting respiration in yeast
Apparatus for the investigation into factors a affecting respiration in yeast
Yeast (100g/dm^3)
Sucrose solution (0.4moldm^-3)
Thermometer
Access to hot and cold water
1dm^3 beaker for carrying water
20cm^3 syringe
Weight
Trough
Marker pen
Glass rod
Timer
Why is a weight used in this practical?
So that the syringe doesn’t float to the top
In which direction should the nozzle of the syringe be facing and why?
Upward to that the yeast doesn’t leak out
method
1.) mix hot and cold water in the trough to attain the chosen temperature. The temperature should be monitored throughout the experiment. Mix in hot water mixed as necessary to maintain the temperature to +-1degrees Celsius.
2.) stir the yeast suspension and draw 5cm^3 into the 20cm^3 syringe
3.)wash he outside of the syringe with running water to remove any yeast solution on the outside of the syringe
4.) draw into the syringe an additional 10cm^3 sucrose solute
5.) pull the plunger back until it almost reaches the end of the syringe barrel
6.) invert the syringe gently to max the contents
7.) place the syringe horizontally in the water bath, ensuring the nozzle is uppermost and place the weight on top of the syringe to hold it in place
8.) allow 2 minutes for the yeast and sucrose to equilibrate to temperature
9.) when gas bubbles energy regularly from the nozzle of the syringe, count the number released in one minute
Results of this practical
Higher temperature = more bubbles released = higher rate of respiration
What is respiration controlled by?
Enzymes
Why does increasing the temperature increase the rate of respiration?
Respiration is controlled by enzymes
Increased temperatures = increased KE of enzymes = more collisions between enzymes and substrates = increased probability of reactions
What might start to happen to the graph at higher temperatures and why?
Level off s enzymes denature
What do the length of range bars tell us?
How repeatable the results are
