Qn: what is the difference between polypeptide and protein?
Can survive longer without food than water
Learning Outcomes– List the chemical elements which make up carbohydrates, fats and proteins (Pure)– Describe and carry out tests for starch, reducing sugars, proteins and fats– State that large molecules are synthesised from smaller basic units– State the roles of water in living organisms
Carbohydrate (Pure)– Organic compounds made up of carbon, hydrogen and oxygen.– The general formula is CmH2nOn– Glucose is C6H12O6– Food sources: Rice, bread, pasta etc.
Types of CarbohydratesMono: 1; Di: 2; Tri: 3; Poly: many• Monosaccharides (single-unit sugar) – Glucose, fructose and galactose• Disaccharides (double-unit sugar) – Maltose, sucrose and lactose• Polysaccharides (many-units of sugar) – Starch, glycogen and cellulose
All of you are seated at your individual seats… Imagine all of you are simple sugars… I am one molecule of glucose.
Monosaccharides (Single sugar) Single sugar Occurrence Glucose Found in all animals Common in plants, Fructose but rare in animals Present in milk sugar Galactose from mammals
Disaccharides (Double Sugars) Double sugars Occurrence Found in sprouting Maltose grains Found in cane sugar Sucrose (common table sugar) Lactose Present in milk sugar from mammals
PolysaccharidesMany smaller basic units of glucosejoined together to form polysaccharides.
Polysaccharides (Complex Sugars) Complex sugars Occurrence Starch Storage form of carbohydrate in plants Glycogen •Storage form of carbohydrate in animals •Stored mainly in liver and muscles Cellulose Structural form of carbohydrate in plants
Permeability• Monosaccharides are small sugar molecules that can pass through the visking tubing.• Disaccharides and polysaccharides are large, complex molecules that CANNOT pass through the visking tubing.
What are reducing sugars?• Sugars that can produce a brick-red precipitate when boiled with Benedict’s solution are called reducing sugars.• ALL monosaccharides are reducing sugars.• Glucose, maltose and lactose are examples of reducing sugars.• Sucrose is NOT a reducing sugar.
Test for Reducing Sugars (Benedict’s Test) Add an equal amount of Benedict’s solutionAbout 2cm3 oftest solution (In this case:reducingsugars e.g.glucose) Brick- Red precipitate Heat in water bath
Benedict’s Test for Reducing SugarStep 1: Add 2cm³ of Benedict’s solution to 2cm³ of sample. Shake well to mix.Step 2: Place test tube in a water bath containing boiling water for 5 mins.Step 3: Observe the change in colour and record your observations.
Benedict’s Test for Reducing Sugar Colour Change Conclusion Remains blue Reducing sugar absentBlue to brick-red Reducing sugar precipitate PRESENT
Benedict’s Test – Quantitative Test Amount of Reducing Colour Change Sugar Present Traces of reducing Blue to green mixture sugarBlue to yellow or orange Moderate amount of precipitate reducing sugar Blue to brick-red or Large amount oforange-red precipitate reducing sugar
Iodine test for StarchStep 1: Add a few drops of iodine solution to sample on a white tile(note: iodine solution = iodine + potassium iodide solution)Step 2: Observe and record your observations. Colour Change Conclusion Remains brown Starch absent Brown to blue-black Starch colour PRESENT
Fats / Lipids (Pure)• Organic compounds made up of carbon, hydrogen and oxygen.• No general formula for fats.• Found in butter, cheese, fatty meat, nuts, oil etc.
FatsFormed from smaller basic units of fatty acids and glycerol.
Test for Oil/ Fats(Ethanol/ Alcohol Emulsion Test) Add 2cm3 of Add 2cm3 of ethanol water Shake mixture thoroughly 2 layers of White immiscibleOil droplet emulsion liquid click
Ethanol Emulsion TestFor liquid food:Step 1: Add 2cm3 of ethanol to a few dropsof the sample. Shake the mixture wellfor about 5 mins.Step 2: Add 2cm3 of water to the mixtureand shake it.Step 3: Observe and record observations. Observation ConclusionSolution remains clear Fats absent Cloudy white emulsion Fats PRESENT
For solid food:Step 1: Cut the sample into small pieces and place the pieces in a test tube.Step 2: 2cm3 of ethanol is added. Shake well for 5 mins.Step 3: Allow the solid particles to settle.Step 4: Decant ethanol portion to another test tube containing 2cm3 of water.
DecantEthanol Only pour off the top layer of ethanolSolid particles
For solid food:Step 5: Observe and record your observations. Observation Conclusion Remains clear Fats absent Cloudy white emulsion Fats PRESENT
Test for Proteins (Biuret test) – 1st method Allow Add 1% Add 1cm3 of mixture to CuSO4 drop NaOH stand for by drop 5minSample to Shake mixture Shake afterbe tested: thoroughly each dropin this case, Violet colourEgg white(2cm3) click
Biuret Test for Proteins (1st Method)Step 1: Add 1 cm3 of sodium hydroxide solution to 2 cm3 of sample. Shake well.Step 2: Add 1% copper(II) sulfate solution, drop by drop, gently shaking after each dropStep 3: Observe and record observations Colour Change Conclusion Remains blue Proteins absent blue to violet Proteins PRESENT
Test for Proteins (Biuret test) – 2nd method Allow Add 2cm3 of mixture to Biuret solution stand for 5minSample to Shake mixture wellbe tested:in this case, Violet colourEgg white(2cm3) click
Biuret Test for Proteins (2nd Method)Biuret solution = sodium hydroxide + copper(II) sulphate solutionStep 1: Add 2 cm3 of Biuret solution to 2 cm3 of the sample. Shake well.Step 2:Observe and record observations after 5 minutes. Colour Change Conclusion Remains blue Proteins absent blue to violet Proteins PRESENT
Functions of Water Water is a main solvent used in the body to dissolve substances.1. Transport of dissolved substances around body – Digested food from small intestine to other parts of the body – Waste products from cells to excretory organs for removal – Hormones from glands to different parts of the body as required
2. Key component of – Protoplasm – Digestive juices – Blood – Tissue fluid3. Control body temperature (cools body during evaporation of sweat)4. Required for chemical reactions to take place in. Eg. digestion!!! Prevent dehydration is NOT a function of water
Functions of Water in Plants1. Raw material for photosynthesis2. Maintain the turgidity of plant cells in order to keep the plant upright3. Transport of mineral salts from roots to leaves via xylem4. Transport food substances from leaves to other parts of plants via phloem