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Cytology

In basic aqueous medium, non-reducing
sugars do not generate any compounds Procedure
containing an aldehyde group. Due to (a) Prepare two solutions, one from
that, it cannot donate electrons to other sweet potatoes and another one
molecules; hence, cannot act as a reducing from coconut pulp.
agent. Sucrose is the most common non- (b) Carry out biochemical test using
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reducing sugar. The linkage between the the given reagents and apparati to
glucose and fructose units in sucrose, which investigate food substances present
involves aldehyde and ketone groups, is in each of the solutions.
responsible for the inability of sucrose to
act as a reducing sugar. A non-reducing Question
sugar does not reduce copper (II) sulphate; 1. State the roles of each food substance
therefore, there is no direct test for it. found in the tested solutions.
However, if it is first hydrolysed to its 2. Prepare a report based on the scientific
constituent monosaccharides, it will then writing skills.
give positive Benedict’s test results.

The basis for non-reducing sugar test Functions of carbohydrates
A non-reducing sugar (sucrose) can (a) Carbohydrates are the main sources
be hydrolysed by heating with dilute of energy in living organisms as they
hydrochloric acid to give glucose and can be oxidised to produce energy. For
fructose, both of which are reducing sugars. example, glucose is the most common
The solution is neutralised with dilute
sodium hydroxide or potassium hydroxide respiratory substrate, which when
so as to give the reducing sugar results with completely oxidised, yields about 38
the Benedict’s test on heating. ATP.
(b) Trioses such as glyceraldehyde
Activity 1.4: Biochemical test for and dihydroxyacetone are used
carbohydrates as intermediates in respiration,

Materials photosynthesis and other carbohydrate
Sweet potatoes, coconut seed, apparati metabolic processes. During respiration
(test tubes, test tube racks, test tube (glycolysis), six carbon sugar splits
holder and brush, beaker, scalpel or to form dihydroxyacetone, phosphate
surgical blade, measuring cylinder,
droppers, mortar and pestle), reagents and phosphoglyceraldehyde, which
(Benedict’s solution, iodine solution, enter the cycle, whereas during dark
dilute hydrochloric acid, dilute sodium reaction of photosynthesis the formed
hydroxide solution, and distilled water), phosphoglyceraldehyde becomes a
and a source of heat source of lipids and proteins.

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