BIOLOGY FROM 4 SCIENCE

CHAPTER 1 : NUTRITION

Lipid is a term collectively use to describe fat,oil and waves like carbohydrate, liquid consist of the element carbon, hydrogen and oxygen but the oxygen proportion is comperative lower and it provide morethan double the energy value.

Lipid has hydrogen, oxygen ratio is 2:1 and lipids are made from difference between fat and oil is that.

At normal temperature fat is solid while oil are liquid but their chemical properties and composition are the same.

For lipid molecules to be formed fatty acid most combine with glycerol in an esterification reaction to give fats and water just like when an acid combines with alcohol its gives salt and water.

An esterification reaction is a reaction between a hydroxyl group and the carboxylic group to form ester. Liquid are insoluble in water but soluble in organic solvent.

FUNCTIONS OF LIPIDS

They are used in the formation of cell membrane eg glycolipids and and phospholipids.
Support the formation of waves in the body of animals
It is insoluble nature prevent the penetration of snake poison in pig
Fatty tissues serves as home for some parasites like tape worm
Help for absorbing certain vitamins like ADCK Caroteinoid
It provide energy during extreme starvation of cell activities.
It serves as storage as cushion and insulator in the body hence preventing excessive heat loss from the body.

FOOD TEST

It is simply the verification of the different food types to given item like carbohydrate, protein, lipid etc. The type of food stored in the cotyledon or endosperm of the seed can be investigated by cashing the seed after being heated with water.

Carbohydrates:

It is divided into reducing sugars and non-reducing sugars. They include monosaccharides and some disaccharides e.g lactose, maltose reducing sugar are tested using benedicts solution or feilling solution. This can be coming out as observed on the table below.

Food items	Procedure	observation	conclusion
Reducing sugar	Put equal amount of 2cm³ reducing sugar solution and add
	Fehlings reagents to a test tube add 4cm³ of reducing add 2cm³ of fehlings reagent bring to boil by shaking continously	Pale blue colour turns green to yellow and finally to a brick-red precipitate	Blue colour that of copper II Sulphate colour change because reducing sugar has reduce copper II ion to copper oxide precipitate formed is copper(I) which is insoluble

Non-reducing Sugar

This include some disaccharide such as sucrose, complex sugar or non-reducing sugar cannot be tested by benedict solution because the result will be negative. The complex sugar first converted to reducing sugar by boiling with dilute hydrochloric acid(HCL). The acid hydrolysis the sugar too.

Sucrose can be converted to glucose and fructose which are acid reducing sugar. Sodium hydrogen carbonate(NaH₂CO₃) is added to the mixture to neutralize the acid. After hydrolysis is non-reducing sugar can then be carried out using feilling solution or benedict solution and the test will be positive.

Food items

Procedure

Observation

conclusion

Complex sugar(non-reducing sugar)	Into a test tube, put 2cm³ of sucrose solution on. Add 1cm² od dilute hydrochloric acid and boil for 30 seconds add sodium hydrogen carbonate. Care fully to neutralize the acid(use your PH paper to check neutral point). Apply benedict’s or fehlings reagents to the contents of your test tube to complete the test	Pale blue turn to yellow and finally a brick red precipitate	Acid hydrolysis sucrose to glucose and fluctose which are all reducing sugar colour changes e.g benedict’s and fehling test above
Starch	Add 3 drops of iodine solution. Potassium iodide and is brown in colour to 3cm³ of 5 percent of starch	The appearance of a blue black colorization a reddish brown colour indicates the presence of glycogen	The blue black shows the presence of starch
Protein	Using a gruge, transfer 3cm³ of meat solution and 2cm³ of million reagent in a test tube health the test tube in water both for 5 minutes	A red deep colour indicates the presence of protein	Protein is present in the plant
Fat and oil emulsion test	Add a few cm³ of ethanol to a small amount of fatty food such as ground bean, groundnut or cooking oil	A Blue black colour was observed	Starch was present
Starch	Into a test tube put 2cm³ of starch suspension and add 2 drops of iodine of potassium iodine solution	Colour changes from brown to blue black	A complete starch iodide compound is formed which blue-black
Lipids	On a filter paper put 2 drops of oil and allow	Oil makes the paper translucent on putting the either after some times it becomes dry.OR put 2 drops of diethyl theithezon the same spot on the paper.	The ether evaporation. Hence making the paper to regain it’s original clean colour.
Second experiment for lipids	Sudan III put 2cm³ of oil in a test tube containing 2cm³ of water add few drops of sudan III and shake	Oil separate from water H₂. Oil is stained red-while H₂O is uncoloured	Oil is less dense than water thus remain floating sudan III stains oil to differenciate it from water.

par Claude Foumtum

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