RP9: Investigation of a variable on the rate of respiration of single celled organisms

Question 1

In this experiment what are investigating

Answer 1

We are investigating the effect of temperature on the rate of respiration in yeast

Question 2

What is yeast

Answer 2

Yeast is a single celled fungus. It can respire aerobically and anaerobically. During aerobic respiration the transport of electrons is linked to the synthesis of ATP in this investigation these electrons will be accepted by substance called methylene blue. when methylene blue accept the electrons changes from blue to colours in this investigation you work at the rate of respiration of yeast at six different temperatures

Question 3

What is a procedure for this experiment

Answer 3

1: put 2 cm³ of the yeast mixture into one of the test tubes and shake it thoroughly
2: please this tube in the correct water bath for three minutes
3: use a clean pet and add 2 cm³ of methylene blue to the test tube
4: immediately remove the test tube, shake for 10 seconds and replace it in the water bath do not shake it again
5: start the timer
6: Record the time taken for the blue colour to disappear in the tube
7: repeat the procedure two more times

Question 4

What does it mean when the colour change occurs from blue to colourless

Answer 4

It means that aerobic respiration is taking place as during aerobic respiration electrons will be accepted by methylene blue. When methylene blue accepts the electrons it changes from blue to colourless.

Question 5

How do you workout the rate of decolourisation

Answer 5

1/time taken

Question 6

You were told to leave the test tubes in the water bath for three minutes explain why

Answer 6

It allows the yeast mixture to calibrate to the temperature of the water bath. it also allows the apparatus to equilibrate

Question 7

You were told to make sure that the water bath temperature stayed at 35°C describe how you monitor the water bath temperature stayed at 35°C

Answer 7

you place a thermometer in the water to monitor the temperature at regular intervals. Then add more hot or cold water depending on if the water bath temperature is above or below 35°C

Question 8

There was no controlled experiments in this investigation describe the control experiment we would set up and explain why this control experiment would be important

Answer 8

you could have a test tube with only glucose and methylene blue. This would ensure that the yeast is causing the colour change.

you could boil the yeast and add methylene blue to denature the yeast To ensure that the yeast is causing the colour change

Question 9

You were told not to shake the teams again instead line shaking the teams would have caused the methylene blue to go blue again suggest why

Answer 9

if you shake the test tubes you would mix the methylene blue with oxygen in the air. This will oxidise the methylene blue (which is colourless) turning it blue again

Question 10

Respiration by The yeast caused the methylene blue to go colourless explain how

Answer 10

methylene blue will become reduced, and the glucose will be oxidised. The electrons from the glucose are donated to the methylene blue.
Methylene blue accept the electrons, once the methylene blue is reduced it will turn colourless this occurs when the yeast respires

Question 11

Use a graph to describe the effect of temperature on the rate of respiration

Answer 11

as the temperature increases the time it takes for the methylene blue to decolourise decreases. the time it takes for methylene blue to decolourise is proportional to the rate of respiration. Therefore as the temperature increases the rate of respiration also increases. until it got to an optimum temperature

Question 12

How would you plot a graph for this information

Answer 12

Y axis: The mean rate to decolourise (S-1)

X axis: Temperature (Degrees Celsius)

Question 13

Why does the red liquid in the respirometer move towards the respiring organism

Answer 13

how do maggots respire oxygen is taken in and the carbon dioxide is given out. The soda line will absorb all of the carbon dioxide produced. This decreases the volume of gas in the experimental tube therefore the pressure of the experimental tube is lower than the pressure in the control tube. And the red liquid for now move towards the experimental cheap as this is where the pressure is lowest

Question 14

How do we set up a control tube

Answer 14

Instead of a respiring organism we set up the control tube where the glass beads and soda lime. No respiration will occur therefore no carbon dioxide will be produced. The pressure in the control to you but will remain the same as before

Question 15

With the yeast practical how do we know whether the experiment is anaerobic or aerobic

Answer 15

The substance given to absorb the material/gas will absorb oxygen is the experiment is anaerobic

Question 16

Suggest one reason why the student left the mixture for one hour after a constant temperature was measured

Answer 16

to make the conditions anaerobic it takes at least one hour for oxygen in the conical flask to be absorbed by the solution (alkaline solution)

Question 17

Suggest a reason why the student left the yeast mixture for one hour before she starts the experiment

Answer 17

to allow temperature to equilibriate. for all of the gases to reach the same temperature.  and therefore the same starting pressure. and for everything to equilibriate

Question 18

What does it mean if a liquid moves away from the yeast in anerobic conditions

Answer 18

do yeast produce carbon dioxide gas which increases the volume of gas in chronicle flask. This increases the pressure in the conical flask therefore the respirometer fluid moves away from the conical flask

Question 19

Why is this experiment subjective

Answer 19

Because the end point is subjective as it is qualitative.

There is also difficulties in seen the colour change in the water bath

Question 20

Why was the yeast and the indicator be left in the water bath for five minutes before the experiment

Answer 20

so that the yeast And the indicator both equilibriate to the test temperature

Question 21

what is the enzyme that removes hydrogen is from (NADH)

Answer 21

Dehydrogenase

Question 22

What does a hydrogen/proton split into

Answer 22

proton and electron

Question 23

at which stages of respiration will the dehydrogenase enzymes be removing a hydrogen from reduced coenzymes

Answer 23

NADH is made in glycolysis, the link reaction, the Krebs cycle. A hydrogen is removed. Also during oxidative phosphorylation dehydrogenase is used to remove a hydrogen from coenzymes