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The aim of this investigation is to find that the concentration of a particular biochemical compound will vary across the different ranges of food substances, in which the compound is found.

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PRACTICAL FOOD TESTS Introduction Many compounds, which occur in living organisms, are organic substances. Organic molecules are relatively large and have unique characteristics allowing them to carry out complex functions. Important categories of organic compounds make up roughly 40% of body mass include carbohydrates, lipids, proteins, nucleic acids and adenosine triphosphate (ATP). Carbohydrates include monosaccharides, disaccharides and polysaccharides these provide most of the chemical energy needed to generate ATP, the principal energy-transferring molecule in living systems. ATP drives metabolic reactions. Lipids are a diverse group of compounds that include triglycerides, phospholipids, steroids and eicosanoids. Triglycerides protect, insulate and provide energy, and are stored. Phospholipids are cell membrane components and eicosanoids modify hormone responses, contribute inflammation, dilate airways and regulate body temperature. Proteins are constructed from amino acids. They give structure to the body, regulate processes and provide protection. Investigation This is a quantative investigation to identify the main classes of Biochemical compounds using samples of some common food substances. Aim The aim of this investigation is to find that the concentration of a particular biochemical compound will vary across the different ranges of food substances, in which the compound is found. ...read more.


Vitamin C 20cm3 of solution to 1cm3 of DCPIP. Fats 2 gm of food substance to 5cm3 ethanol and 5cm3 of water. Protein 2gm protein suspension in 10cm3 of water. This is shaken to dissolve. Then 3cm3 of equal amounts of sodium hydroxide and copper sulphate is added. Reducing Sugar 10cm3 of water solution and 1 gm of solid or liquid. Then add equal volume of benedict's solution. Complex Sugar 1 gm of food substance to 10cm3 of water. Add 10 drops of hydrochloric acid and an excess amount of sodium bicarbonate until it fizzes. Repeat the reducing sugars test. The Results were recorded on a scale of 0 - 5, where 5 shows a high concentration of a chemical compound. No concentration would be 0. Table 2 Results On Common Food Substances CHEESE BUTTER LEMONADE ORANGE JUICE SUGAR BREAD LEMON JUICE EGG WHITE POTATO STARCH 0 0 0 0 0 4 0 0 5 VITAMIN C NO RESULT NO RESULT 2 5 0 0 2 0 NO RESULT FATS 3 5 0 0 0 1 0 0 0 PROTEIN 2 1 0 0 0 1 0 5 1 REDUCING SUGAR NO RESULT NO RESULT 2 0 0 0 0 0 NO ...read more.


The -CHO group is oxidised. Fig 7. Carbonyl Functional Group CHO H C OH HO C OH H C OH H C OH CH2OH * In the benedicts test the CHO group is oxidised, that is, it loses electrons. * The electrons are taken up by the copper in Copper sulphate (blue) to form a brick red precipitate of copper oxide. 2Cu(OH)2 + R-C=O Cu2 O + R.COOH + 2H2O copper hydroxide � copper oxide sugar acid H Ionic Reaction Cu + e Cu (ion) (ion) The reductions of electron turn into a different kind of copper. Complex sugars such as sucrose cannot reduce other chemicals because its chemical structure is slightly different. It is made up from glucose and fructose. The carbon 1 of the glucose becomes buried within the disaccharide and is not free to form the -CHO group. This is why it will not cause a colour change in the Benedicts test. It has to be split into its component monosaccharide first, by dilute acid. Test For Complex Sugar. In testing for complex sugar, firstly it most is hydrolysed to a reducing sugar. Hcl/H2O 1. Complex Sugar Reducing Sugar Hydrolysis Hydrolysis is one of the main reactions in digestion. Fats, proteins etc are broken down. 2.Carry out Benedicts test. ...read more.

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