Beetroot Practical 3 Flashcards
(24 cards)
Outline steps to measure absorbance
Set up a water bath at room temperature.
Prepare 5 test tubes with 2 cm³ alcohol solutions of varying concentrations (100%, 80%, 60%, 40%, 20%).
Use a cork borer to cut 10 identical beetroot discs and blot them dry with paper towels.
Add 2 beetroot discs to each alcohol test tube and seal with a bung.
Place the test tubes in the water bath for 5 minutes, shaking gently every minute.
Remove the beetroot discs after 5 minutes.
Measure the absorbance of each solution using the colorimeter.
Record absorbance values in a suitable table.
What is the point of experiment
How factors such as alcohol effect permeability of cell membrane , at higher concentrations proteins in the cell membrane denature so more pigment will be released so shows importance of phospholipid bilayer in cellular function
What is the colorimeter used for
To measure absorption of the pigment which allows quantitive data to represent the relationship between alcohol concentration and permeability of cell membrane
Out line the steps of part one of the experiment
Prepare 6 test tubes with 10 cm³ solutions of varying concentrations of beetroot extract (0%, 20%, 40%, 60%, 80%, 100%).
Mix beetroot extract and water to create the 10cm cubed .
E.g if you have 20 percentage beetroot extract that will be 2cm3 of extract diluted with 8 cm3 of water
Use a colorimeter and calibrate it with pure water for zero absorbance.
Measure and record the absorbance of each solution using the colorimeter.
Record data in Table 1.
What are we measuring in part one
You’re testing how much light absorbance occurs when beetroot pigment is diluted with different volumes of water.
What are we measuring in part 2
How much beetroot extract is absorbed in different volumes of alcohol ,higher concentrations create more damage to cell membrane hence why we get more absorption
What was the independent variable in the beetroot experiment?
Alcohol concentration
What was the dependent variable in the beetroot experiment?
The absorbance of the solution (measured using a colorimeter)
Name three control variables in the beetroot experiment and how you controlled them.
Size of beetroot discs – Use a cork borer to ensure uniform size.
Time in solution – Use a timer to ensure all test tubes were left in alcohol for the same time.
Temperature – Use a water bath to maintain a constant temperature
Why were the beetroot discs washed thoroughly before the investigation
To remove any pigment released due to handling or cutting the beetroot.
Why were you instructed to shake the test tubes every minute
To ensure the beetroot discs were evenly exposed to the alcohol solution
Why would results differ if cooked beetroot was used instead of fresh beetroot?
Cooking denatures membrane proteins and disrupts the phospholipid bilayer, leading to more pigment leakage even at low alcohol concentrations.
How would a decrease in temperature by 5°C affect the results?
Membrane fluidity would decrease, reducing pigment leakage, and absorbance values would likely be lower.
Why might two students conducting the same experiment get different results?
Potential reasons include slight variations in the size of beetroot discs, inaccuracies in measuring alcohol concentrations, or differences in shaking methods.
Why does alcohol increase membrane permeability
Alcohol disrupts the phospholipid bilayer and denatures proteins, making the membrane more permeable to pigment leakage
How would you check if a point on the graph is an anomaly?
Repeat the experiment for that alcohol concentration to verify if the result is consistent.
Why does the curve level off at high alcohol concentrations
At high alcohol concentrations, the membranes are fully disrupted, so no additional pigment can leak out.
Why is it important to control the size of the beetroot discs?
To ensure consistent surface area for diffusion, as larger discs would release more pigment so results won’t be comparable
What is betalin, and why is it significant in this experiment?
Betalin is the red pigment stored in the beetroot vacuole, and its leakage is used to assess membrane permeability.
How does temperature affect membrane permeability?
Higher temperatures increase membrane fluidity, leading to more pigment leakage, while lower temperatures decrease fluidity.
What is the purpose of calibrating the colorimeter with water?
To set a baseline absorbance of zero, ensuring accurate readings for the test solutions.
Why do we seal test tube with bung
Prevent alcohol evaporation and to make sure alcohol concentration stays constant throughout experiment
Why do we use water bath in part two but not part one?
Because in part one we measure light absorption and temperature does not effect this In part two we want to measure pigment absorption which represents permeability of cell membrane and is effected by temperature so we use water bath to ensure results are comparable
Solutions with more beetroot pigment show …
Higher absorption
