Quantitative tests for biological molecules Flashcards
What does Benedict’s reagent detect?
The presence of reducing sugars
If there is more sugar present in a sample what is likely to happen?
An increase in the amount of precipitate and a decrease in the amount of copper (II) ions remaining in the solution.
How does a colorimeter work?
By shining light through a sample
When detecting the presence of reducing sugars what is used to separate the precipitate and the solution?
A centrifuge
Once the precipitate is removed what is it called?
The supernatant
What is the supernatant placed into before being put in the colorimeter?
A cuvette
Why must a greasy fingerprint not be left on the cuvette?
It could effect the transmission of light.
What are often used for greater accuracy when using a colorimeter?
A colour filter
What colour filter is used to when testing reducing sugars in a colorimeter? Why is this?
Red.
The solution absorbs red light and reflects blue light.
If there is a lot of unreacted copper sulphate in the supernatant what happens when it is tested?
The absorption of red light and percentage transmission is low.
If there is little unreacted copper sulphate in the supernatant what happens when it is tested?
The absorption of red light is low and the percentage transmission is high.
What is used as a blank sample when testing the samples?
Water is used as a blank sample to zero the colorimeter before the next reading.
What is the name of the graph produced from the results of the reducing sugars experiment?
A calibration curve.
What can a calibration curve be further used for?
To estimate the concentration of glucose from a desired percentage of transmission.
What is a biosensor used for?
They take a biological or chemical variable which cannot easily be measured, and convert it to an electrical signal.
