Testing For Carbohydrates

Question 1

what are some examples of reducing sugars?

Answer 1

all monosaccharides and some disaccharides

Question 2

what is the chemical test for reducing sugars?

Answer 2

Benedict’s reagent (an alkaline solution of copper 2 sulphate)

Question 3

how is a benedicts reagent test conducted?

Answer 3

1. place sample in boiling tube. liquid or grind it up.
2. add an equal volume of Benedict’s reagent.
3. heat mixture gently in boiling water bath for 5 minutes.

Question 4

what shows a positive reducing sugar?

Answer 4

it will turn from blue to a brick red precipitate.

Question 5

what is the chemical test for non reducing sugars?

Answer 5

benedicts reagent

Question 6

what is an example of a non reducing sugar?

Answer 6

sucros

Question 7

how do you conduct benedict reagents test for non reducing sugars?

Answer 7

1. the sucrose must be hydrolysed to glucose and fructose by boiling with dilute hydrochloric acid.
2. add an equal volume of benedict’s reagent and heat inn water bath
3. positive result will turn brick red precipitate from blue.

Question 8

what is the chemical test for starch?

Answer 8

iodine strips.

Question 9

how do you carry out an iodine test?

Answer 9

1. a few drops of iodine dissolved in potassium iodide solution are mixed with sample.
2. if starch is present, it will turn from yellow to blue black.

Question 10

why are reagent strips useful?

Answer 10

can estimate a quantitative value for the concentration of sugar.

Question 11

what is a colorimeter?

Answer 11

a piece of equipment used to quantitatively measure the absorbance, or transmission of light

Question 12

how do you calculate % absorbance from a % transmission reading?

Answer 12

absorbance = 2 - log (%Transmittion)

Question 13

how do you calibrate a colorimeter?

Answer 13

press and hold CAL button. when red LED flashes, release the button. it is calibrated once it stops flashing.

Question 14

what are biosensers?

Answer 14

instrument used to determine the presence and concetration of molecules using biological components.

Question 15

what does analyte mean?

Answer 15

the analyte is the compound under investigation.

Question 16

what are the stages of a biosenser?

Answer 16

1. molecular recognition- a protein is immobilised to a surface. this will bind to specific molecule under investigation.
2. transduction - the interaction will cause change in a transducer. a transducer detects change and produces a response
3. display - this then produces a visibile qualitative or quantitaive signal.