Testing For Biological Mol.

Question 1

Define a qualitative test

Answer 1

Testing fro the presence or absence of a particular biological molecule

Question 2

Describe the test for starch

Answer 2

Iodine test= add drops of iodine solution to solution

Results= dark blue/black- starch present

Question 3

Describe the procedure for the test of reducing sugar

Answer 3

1) add Benedicts solution to the sample in the test tube
2) shake mixture and HEAT (don’t boil)
3) observe colour change

Question 4

What is the result of a reducing sugar experiment

Answer 4

Red precipitate/orange = high amounted of RS

Blue precipitate= low amounts of RS

Question 5

What is the procedure for non reducing sugars

Answer 5

1) boil solution with dilute HCL
2) neutralise with sodium carbonate
3) repeat Benedicts test

Question 6

Name an example of:

• a non reducing sugar
• reducing sugar

Answer 6

1) sucrose

2) maltose

Question 7

How are test strips used

Answer 7

The enzymes react with the reducing sugar to form coloured compounds

Question 8

Give two examples of test strips

Answer 8

Clinistix

Diostix

Question 9

Name 4 advantages of test strips for reducing sugars

Answer 9

Quick
Just need a urine sample
Many tests can be done at once
No labs required

Question 10

Name 4 disadvantages for reducing sugar test strips

Answer 10

Subjective in terms of colours
Colour blindness
Not many intermediate values
Semi quantitative

Question 11

Name a monomer that gives a positive result with Benedictuss

Answer 11

Glucose or maltose

Question 12

Describe the test for protein

Answer 12

BIURETS REAGENT
Add to solution and shake thoroughly

Lilac=proteins present

Question 13

What is in biurets reagent

Answer 13

Copper sulphate and sodium hydroxide

Question 14

Describe the test for lipids

Answer 14

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

Question 15

What is a quantitative test

Answer 15

Used when u want to know the concentration or mass of a biological molecule in a solution

Question 16

What is a colorimeter

Answer 16

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

Question 17

The more sugar present ina sample….

Answer 17

The more copper sulphate will be used up

Less light will be absorbed by the remaining solution and the more light will be transmitted

Question 18

The less sugar…

Answer 18

The less copper ions will react with the sugar

More light absorbed and less light transmitted

Question 19

What solution can be used to zero the colorimeter

Answer 19

Distilled water

Unreacted benedicts

Question 20

Describe how a colorimeter could be calibrated and then used to measure an unknown concentration of RS

Answer 20

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

Question 21

Why is a red filter used in a colorimeter

Answer 21

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

Question 22

What must be done to the solution before using a colorimeter

Answer 22

The precipitate must be filtered out

Question 23

Describe how the conc of a reducing sugar can be measured using a colorimeter

Answer 23

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

Question 24

Name 3 control variables when using colorimeter for testing unknown conc

Answer 24

• same volume of glucose solution
• use same conc of benedicts
• heat for same length of time

Question 25

How does a bio sensor work

Answer 25

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.

Question 26

What is the analysts

Answer 26

The substance being studied, e.g. DNA /protein

Question 27

What occurs during molecular recognition

Answer 27

The substance is immobilised on the test area (because it binds to a complementary target)

Question 28

What does thin layer chromatography use

Answer 28

A thin uniform layer of silica gel which is coated onto a material

Question 29

What is the distance travelled in chromatography determined by

Answer 29

Solubility of the compound moving in the solvent

The interaction between the compound moving and the silica gel

Question 30

Describe TLC

Answer 30

Sample is placed on the stationary phase
Put in solvent
Sample is carried by the solvent up the chromatogram

Question 31

What is the formula for RF Value

Answer 31

Rf value= distance travelled by component/distance travelled by solvent