Testing For Biological Mol. Flashcards
Define a qualitative test
Testing fro the presence or absence of a particular biological molecule
Describe the test for starch
Iodine test= add drops of iodine solution to solution
Results= dark blue/black- starch present
Describe the procedure for the test of reducing sugar
1) add Benedicts solution to the sample in the test tube
2) shake mixture and HEAT (don’t boil)
3) observe colour change
What is the result of a reducing sugar experiment
Red precipitate/orange = high amounted of RS
Blue precipitate= low amounts of RS
What is the procedure for non reducing sugars
1) boil solution with dilute HCL
2) neutralise with sodium carbonate
3) repeat Benedicts test
Name an example of:
- a non reducing sugar
- reducing sugar
1) sucrose
2) maltose
How are test strips used
The enzymes react with the reducing sugar to form coloured compounds
Give two examples of test strips
Clinistix
Diostix
Name 4 advantages of test strips for reducing sugars
Quick
Just need a urine sample
Many tests can be done at once
No labs required
Name 4 disadvantages for reducing sugar test strips
Subjective in terms of colours
Colour blindness
Not many intermediate values
Semi quantitative
Name a monomer that gives a positive result with Benedictuss
Glucose or maltose
Describe the test for protein
BIURETS REAGENT
Add to solution and shake thoroughly
Lilac=proteins present
What is in biurets reagent
Copper sulphate and sodium hydroxide
Describe the test for lipids
Emulsion test=
1) crush sample if needed
2) add ethanol to sample
3) shake
4) pour into water
Result= if a lipid is present a cloudy white emulsion is formed
What is a quantitative test
Used when u want to know the concentration or mass of a biological molecule in a solution
What is a colorimeter
A device that shines a beam of light through a sample
The photoelectric cell picks up the light that has passed through, a sample of the solution is placed between the light and the cell in a cuvette
The more sugar present ina sample….
The more copper sulphate will be used up
Less light will be absorbed by the remaining solution and the more light will be transmitted
The less sugar…
The less copper ions will react with the sugar
More light absorbed and less light transmitted
What solution can be used to zero the colorimeter
Distilled water
Unreacted benedicts
Describe how a colorimeter could be calibrated and then used to measure an unknown concentration of RS
1) Use a red filter (which absorbs all the colours of the spectrum except red)
2) Zero colorimeter
3) Construct a calibration curve using known concentrations
4) test unknown sample
5) read from the curve to determine an unknown conc
Why is a red filter used in a colorimeter
All other light is absorbed apart from red
This only transmit red light to the blue solution in the cuvette no blue light will be transmitted
Red light is absorbed
This maximises absorption of light
What must be done to the solution before using a colorimeter
The precipitate must be filtered out
Describe how the conc of a reducing sugar can be measured using a colorimeter
1-using known concentrations 2-use the Same volume of reducing sugar and benedicts 3-heat with benedicts 4-colour change 5-filter off precipitate 6-zero colorimeter with a blank 7-use red filter 8-record transmission/absorbance 9-plot calibration curve 10-read off graph
Name 3 control variables when using colorimeter for testing unknown conc
- same volume of glucose solution
- use same conc of benedicts
- heat for same length of time
How does a bio sensor work
The catalyst converts the substrate into the product
A transducer senses the physical changes and converts it to an electrical signal which is amplified and processed and it can then be viewed on a display screen.
What is the analysts
The substance being studied, e.g. DNA /protein
What occurs during molecular recognition
The substance is immobilised on the test area (because it binds to a complementary target)
What does thin layer chromatography use
A thin uniform layer of silica gel which is coated onto a material
What is the distance travelled in chromatography determined by
Solubility of the compound moving in the solvent
The interaction between the compound moving and the silica gel
Describe TLC
Sample is placed on the stationary phase
Put in solvent
Sample is carried by the solvent up the chromatogram
What is the formula for RF Value
Rf value= distance travelled by component/distance travelled by solvent
