Download - Nutrients 2012
NUTRIENTS
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
1. Carbohydrates
2. Proteins
3. Fats
4. Water
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 Carbohydrates
Mono: 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
Fructose
Galactose
Found in all animals
Common in plants, but rare in animals
Present in milk sugar from mammals
Disaccharides (Double Sugars)
Double sugars Occurrence
Maltose
Sucrose
Lactose
Found in sprouting grains
Found in cane sugar (common table sugar)
Present in milk sugar from mammals
Polysaccharides
Many smaller basic units of glucosejoined together to form
polysaccharides.
Polysaccharides (Complex Sugars)Complex sugars Occurrence
StarchStorage form of
carbohydrate in plants
Glycogen
•Storage form of carbohydrate in animals•Stored mainly in liver and muscles
CelluloseStructural form of
carbohydrate in plants
starch
glucose
maltose
starch
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.
About 2cm3 of test solution (In this case: reducing sugars e.g. glucose)
Heat in water bath
Brick- Red precipitate
Add an equal amount of Benedict’s solution
Test for Reducing Sugars(Benedict’s Test)
Benedict’s Test forReducing Sugar
Step 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 forReducing Sugar
Colour Change Conclusion
Remains blueReducing sugar
absent
Blue to brick-red precipitate
Reducing sugarPRESENT
Benedict’s Test – Quantitative Test
Colour ChangeAmount of
Reducing Sugar Present
Blue to green mixtureTraces of reducing
sugar
Blue to yellow or orange precipitate
Moderate amount of reducing sugar
Blue to brick-red or orange-red precipitate
Large amount of reducing sugar
Iodine test for Starch
Step 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 colour
StarchPRESENT
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.
Fats
Formed from smaller basic units of fatty acids and glycerol.
Fats / Lipids
Fatty acids + glycerol
Fats / Lipids
Oil droplet
Add 2cm3 of ethanol
Add 2cm3 of water
Shake mixture thoroughly
White emulsion
2 layers of immiscible liquid
Test for Oil/ Fats(Ethanol/ Alcohol Emulsion Test)
click
Ethanol Emulsion TestFor liquid food:Step 1: Add 2cm3 of ethanol to a few drops of the sample. Shake the mixture
well for about 5 mins.
Step 2: Add 2cm3 of water to the mixture and shake it.
Step 3: Observe and record observations.Observation Conclusion
Solution 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.
Decant
Solid particles
Ethanol
Only pour offthe top layer
of ethanol
For solid food:
Step 5: Observe and record your observations.
Observation Conclusion
Remains clear Fats absent
Cloudy white emulsion Fats PRESENT
Kwashiorkor
Proteins (Pure)
• Organic substances made up of carbon, hydrogen, oxygen and nitrogen
• Sulfur may also be present
Amino acids Proteins are built up from smaller
basic units of amino acids
Amino acids to polypeptide
Many amino acidslinked together to form polypeptide.
Polypeptide to proteins Polypeptide
Folding of this long chain of amino acids to
give a unique three-dimensional shape
Protein is formed
http://intro.bio.umb.edu/111-112/111F98Lect/folding.html
Summary
Amino acids
Polypeptides
Proteins
Aminoacids
Proteins
Polypeptides
Test for Proteins(Biuret test) – 1st method
Sample to be tested: in this case, Egg white (2cm3)
Add 1cm3 of NaOH
Add 1% CuSO4 drop by drop
Shake mixture thoroughly
Shake after each drop
Allow mixture to stand for 5min
Violet colour
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 drop
Step 3: Observe and record observationsColour Change Conclusion
Remains blue Proteins absent
blue to violet Proteins PRESENT
Test for Proteins(Biuret test) – 2nd method
Sample to be tested: in this case, Egg white (2cm3)
Add 2cm3 of Biuret solution
Shake mixture well
Allow mixture to stand for 5min
Violet colour
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
Summary
Water
In mammal, ~70% of body weight is water
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 fluid
3. 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 Plants
1. Raw material for photosynthesis
2. Maintain the turgidity of plant cells in order to keep the plant upright
3. Transport of mineral salts from roots to leaves via xylem
4. Transport food substances from leaves to other parts of plants via phloem
The End