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N U T R I E N T S (FoOd tEsTs (Experiment 1 : testing for reducing sugars
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N U T R I E N T S
The need for water
As an important constituent of the body and a solvent
(1) Water is the major component of the cytoplasm of cells, tissue fluid, digestive juices and blood
(2) most chemical reaction take place
(3) prevents crenation of animal cells and maintain turgidity of plant cells
As a transport medium for soluble substances
(1) to transport dissolved substances such as digested products from the small intestine to other parts of the body and waste products from the cell for removal from the body
(2) transport mineral salts up the plant in the xylem vessels and distribute food substances made by leaves to other parts of the plant
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Carbohydrates
are organic molecules made up of the elements carbon, hydrogen and oxygen.
Serves as the body's primary source of energy
Monosaccharides
-small molecules that cannot be broken down further
-able to move across cell surface membranes and be taken up by cells
examples ; glucose
fructose
galactose
- they all have the same chemical formula but their atoms are arranged differently within the molecules
Disaccharides
-consists of two single sugar molecules covalently bonded to each other
-formed by a condensation reaction
examples; maltose
sucrose
lactose
Polysaccharides
- made up of many single sugars covalently bonded together
- formed by a condensation reaction
examples:
**(a) Starch **
-storage units in plants and can be broken down to glucose molecules to provide energy for cell activities
- produced in plants
** (b)Cellulose**
-forms cell walls that provides structural support for cells
-cannot be digested by humans
-present in cell walls
** (c) Glycogen**
-storage unit in animals and can be broken down into glucose molecules to provide energy for cell activities
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Condensation reaction: a chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water
Hydrolytic reaction: a reaction in which a water molecule is needed to break up a complex molecule into smaller molecule
Fats
Are organic molecules made up of the elements carbon,hydrogen and oxygen.They contain much greater number of hydrogen atoms as compared to oxygen atoms .
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Proteins
Are organic molecules made up of carbon,hydrogen,oxygen,nitrogen and sometimes sulfur
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Proteins can be obtained form animal and plant foods such as milk, eggs, meat, and nuts. However, they are too large to be taken up by cells hence they are digested into polypeptides and subsequently amino acids by enzymes via hydrolytic reaction
FoOd tEsTs
Experiment 1 : testing for reducing sugars
(all monosaccharides and disaccharides except sucrose)
Place 2cm3 of benedicts solution and 2cm3 of food sample in a test tube. Shake the mixture, place test tube in boiling water bath for 2 to 3 min and observe colour change.
The solution remains blue: No reducing sugar present
The solution turns from blue to brick red precipitate ; Reducing sugar present
Experiment 2: Iodine test (for starch)
Add few drops of iodine solution to the food sample and observe colour change
Iodine solution remains brown: no starch present
Iodine solution turns blue-black: Starch is present
Experiment 3: Emulsion Test for fats
For Liquid food, add 2cm3 of ethanol to food sample in a test tube and shake thoroughly. Add 2cm3 of water to mixture and shake thoroughly and observe the change
For Solid food, cut the food sample into small pieces, place them in a test tube and add 2cm3 of ethanol and shake thoroughly.Decant the ethanol by poruing the top layer of the ethanol into another test tube with 2cm3 of water. Shake thoroughly and observe the change
Ethanol solution remains clear: no fats present
Clear Ethanol solutions turns cloudy with white emulsion : Fats present
Experiment 4: Biuret Test for proteins
Add 2cm3 of sodium hydroxide and 2cm3 of liquid food sample in a test tube. Shake it thoroughly. Add 1% copper (II) sulfate solution drop wise while shaking the mixture.After every drop observe colour change
Copper(II)Sulfate remains blue: no protein present
Blue copper(II) turns violet : Proteins present