Testing for Carbohydrates Flashcards
How do you test for starch?
- drops of iodine (dissolved in potassium iodine solution)
- iodine forms complex with the helical structures of amylose and amylopectin
- turns blue-black
What are examples of reducing sugars?
- all monosaccharides
- maltose and lactose
What are examples of non-reducing sugars?
- some disaccharides e.g. sucrose
- polysaccharides
How do you test for a reducing sugar?
- add benedict’s solution
- heat it
How can we use the Benedict’s test semi-quantitatively?
- colour change indicates concentration ( but not exact value)
How can we use the Benedict’s test qualitatively?
- the reducing sugar is there or isn’t (no indication of amount)
How does the Benedict’s test work?
- if a reducing sugar is present it reduces the solution when heated from CU2+ to CU+ ions changing the colour to brick red.
How is the Benedict’s test modified to test for non-reducing sugars?
- heat with hydrochloric acid to hydrolyse glycosidic bond
- neutralise it with sodium hydrogen carbonate
- then add bendicts solution
What do the Benedict’s test and the reagent test strip methods of testing have in common?
- both have colour change
- both have reaction of reduction
Describe the features of enzymes essential to their role as components in a biosensor?
- molecular recognition
- enzymes immobilised to surface to bind to specific molecule
- specific active site to specific substance
Explain why an iodine test is used in experiments to show that plants require light for photosynthesis
- add iodine solution and leaf in light will turn blue-black due to present of starch
- starch is a product of photosynthesis
- starch is stored in the leaves
Suggest how reagent strips might be useful in the management of the medical condition diabetes, where a person’s blood sugar level can become too high
- reagent test strips can test for amount of glucose in blood
- can determine concentration of sugar
- so if blood sugar level is too high diabetic can be easily alerted
