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