Topic 3: Chapter 4

Nutrients Nutrients – – Part 1Part 1

The The need need for for

food food + +

CarboCarbohydrathydrat

eses

Chemicals and Reactions that take place in the

cell.• Living organisms contains huge amount of

Macromolecules (large molecules)

• Chemical activities that take place in a cell is known as metabolism.

• Metabolic reactions are categorized as anabolic reactions and catabolic reactions.

Anabolic & Catabolic Reactions

• Anabolic reactions build up large molecules from simple molecules.

• Catabolic reactions break down larger molecules into smaller molecules.

Illustration of Anabolic & Catabolic Reactions

H20 Nitrate Phosphate

Sunlight CO2

Carbohydrates(e.g. Glucose)

Photosynthesis

Illustration of Anabolic & Catabolic Reactions

Nitrate Phosphate

Lipids

Carbohydrates(e.g. Glucose)

Protein

Eat

Digestion

Absorption

Why do organisms need food?

1) To provide energy for the vital activities of the body via respiration.

Physical movement, Digestion, Excretion, etc.

2) To synthesize new protoplasm – for growth & repair, & for reproduction.

3) To maintain good health – prevent deficiency disease.

Vit. C, Calcium, etc.

Nutrients• Chemical substances in food that nourish the body.• They provide energy & raw materials needed by

the body.

(A) Organic Nutrients(A) Organic Nutrients(Contains Carbon)(Contains Carbon)

(A) Organic Nutrients(A) Organic Nutrients(Contains Carbon)(Contains Carbon)

(B) Inorganic Nutrients(B) Inorganic Nutrients(does not contain Carbon)(does not contain Carbon)

(B) Inorganic Nutrients(B) Inorganic Nutrients(does not contain Carbon)(does not contain Carbon)

1)1) CarbohydratesCarbohydrates2)2) FatsFats3)3) ProteinsProteins4)4) VitaminsVitamins5)5) Dietary FibreDietary Fibre

1)1) WaterWater2)2) Mineral SaltsMineral Salts

A(1): Carbohydrates

• Organic compounds made up of the elements carbon (C), hydrogen (H) & oxygen (O).

• The hydrogen & oxygen atoms are present in the ratio 2:1.

• Generalized formula: CnH2mOm.

A(1): Functions of Carbohydrates

a) as a substrate for respiration provide energy for cell activities

b) to form supporting structures e.g. plant cell walls

c) to be converted to other organic compounds such as amino acids and fats

d) for the formation of nucleic acid e.g. DNA

e) to synthesize lubricants e.g. mucus – Carbo + Protein)

f) to produce the nectar in some flowers

A(1): Sources of Carbohydrates

•Broken down quickly to provide energy for the body

• Found naturally in food (Fruits, Milk, etc.)

• Found in processed or refined food ( Candy, Syrup, etc.)

•Lack Vitamins, Minerals & Fibres

•Made of sugar molecules strung together in long complex chains

• Majority of carbohydrates are from complex carbohydrates and naturally occurring sugars.

•Provides Vitamins, Minerals & Fibres

A(1): Groups of Carbohydrates

CarbohydratesCarbohydrates

Polysaccharides (complex carbohydrates)

Polysaccharides (complex carbohydrates)

Disaccharides (double sugars)

Disaccharides (double sugars)

Monosaccharides(single sugars)

Monosaccharides(single sugars)

e.g. glucose fructose, galactose

e.g. glucose fructose, galactose

e.g. starch, glycogen, cellulose

e.g. starch, glycogen, cellulose

e.g. Sucrose, Maltose, Lactose

e.g. Sucrose, Maltose, Lactose

• Simple sugars, sweet

• Smallest basic unit.

• ALL with general formula C6H12O6.

- But differ in arrangement of atoms in molecules.

Monosaccharides(single sugars)

Monosaccharides(single sugars)

Disaccharides(double sugars)

Disaccharides(double sugars)

• Simple sugars, sweet

• Formed when 2 monosaccharides are joined together by condensation.

• ALL with general formula C12H22O11.

Condensation

• Chemical reaction in which

• A water molecule is needed

• to break up a complex molecule into smaller molecules

• Chemical reaction in which

• A water molecule is needed

• to break up a complex molecule into smaller molecules

• Chemical reaction in which

• 2 simple molecules are joined together to form a larger molecule

• with the removal of water

• Chemical reaction in which

• 2 simple molecules are joined together to form a larger molecule

• with the removal of water

Hydrolysis

Condensation: Formation of

LactoseLactose

• occurs naturally in milk (milk sugar). • broken down by the enzyme “lactase” during

digestion to yield glucose and galactose by hydrolysis• When milk sours, bacteria converts lactose to lactic

acid

Condensation: Formation ofMaltase

Maltase

• Malt Sugar• Important component in the process of fermenting

barley that can be used for brewing beer.• broken down by the enzyme “maltase” during

digestion to yield 2 glucose molecules by hydrolysis

Condensation: Formation ofSucrose

Sucrose

• occurs naturally in sugarcane (cane sugar), sweet fruits, honey and certain storage roots (e.g. carrots).

• Not found in mammals

Hydrolysis: Breaking down ofSucrose

Sucrose

+

enzyme

glucose fructosesucrose water

+

• broken down by the enzyme “sucrase” / “invertase” during digestion to yield glucose and fructose by hydrolysis

Polysaccharides(complex carbohydrates)

Polysaccharides(complex carbohydrates)

• Consists of many monosaccharide molecules joined together by condensation.

• Starch, Glucogen and Cellulose are complex carbohydrates which are made up of numerous glucose molecules condensed together.

starch

Polysaccharides(complex carbohydrates)

Polysaccharides(complex carbohydrates)

Starch Starch

• Long straight or branched chains of glucose molecules

• Made and stored in plants but not in animals

starch

Polysaccharides(complex carbohydrates)

Polysaccharides(complex carbohydrates)

Cellulose Cellulose

• Long straight chains of glucose molecules

• But different linkages from starch.

• Main part of plant cell wall

• Forms fibre in the diet of mammals

starch

Polysaccharides(complex carbohydrates)

Polysaccharides(complex carbohydrates)

Glycogen Glycogen

• Highly branched chains of glucose

• Made and stored in animals and fungi but not in plants

Storage Glucose

• Starch

• Stored in leaves, tubers and roots

Plants

Animals• Gycogen

• Stored mainly in liver and muscles

Glycogen and Starch as storage materials

• Insoluble in water

do not change the water potential in cells

• Large molecules

Unable to diffuse through cell membranes

• Easily hydrolysed to glucose when needed

e.g for tissue respiration

• Compact shapes which occupies less space.

Hydrolysis and Condensation

maltase maltase maltase maltase

Starch (in plants)Starch (in plants)

MaltoseMaltose

GlucoseGlucose

Hydrolysis in the mouth

Hydrolysis in the guts by enzyme maltase

Condensation in the liver

Glycogen (in animals)Glycogen (in animals)

Consumed and undergoes Digestion

Digestion

Glucogenesis

Food Test (1) Food Test (1) Test for Starch – Iodine Test for Starch – Iodine

TestTest

Procedure:• Add 1-3 drops of iodine solution onto any

substance.

Results:• If starch is present, the iodine solution

changes from yellowish brown to blue-black colour.

Food Test (2) Food Test (2) Test for Reducing Sugars – Test for Reducing Sugars –

Benedict’s TestBenedict’s TestReducing Sugars: Reducing Sugars:

Glucose, Fructose, Maltose, Lactose

Procedure:Procedure:

1. Add 2 cm3 of Benedict’s solution to equal volume of test solution.

2. Mix the solutions by shaking.

3. Heat the mixture in a boiling water-bath for 5 minutes.

4. Prepare a control using distilled water instead of the test solution Benedict’s solution

Food Test (2) Food Test (2) Test for Reducing Sugars – Test for Reducing Sugars –

Benedict’s TestBenedict’s TestResults

Colour change Amount of reducing sugar present

blue to green mixture trace amount

blue to yellow / orange precipitate moderate amount

blue to brick-red precipitate large amount

Food Test (2) Food Test (2) Test for Reducing Sugars – Test for Reducing Sugars –

Benedict’s TestBenedict’s TestResults

Positive Benedict’s test Negative Benedict’s test

Brick Red Precipitate

Blue solution

Topic 3: Chapter 4

Nutrients Nutrients – – Part 2Part 2

FFatatss

LipidsLipids

SteroidsSteroids

ExamplesExamples

Phospholipids Phospholipids FatsFats

For storage of energy

For storage of energy e.g. cholesterole.g. cholesterol

Makes up the Plasma

membrane

Makes up the Plasma

membrane

A(2): FATS• Organic compounds made up of the elements

carbon (C), hydrogen (H) & oxygen (O).

• but unlike carbohydrates, they contain much less oxygen in proportion to hydrogen. (E.g. Beef Fat: Tristearin – C57H110O6)

• No General formula for fats

• Fats fall under the category of LIPIDS

A(2): Composition of a Fat Molecule

• A fat molecule is made up of four parts:

- 1 molecule of glycerol

- 3 fatty acid chains

Glycerol

Fatty Acids

A(2): Breaking down fatsHydrolysi

sHydrolysi

s

• The breaking down of 1 fat molecule involves the addition of 3 water molecules to form 1 glycerol and 3 fatty acid molecules IN THE PRESENCE OF AN ENZYME (Lipase)

A(2): Forming fatsCondensatio

nCondensatio

n

• Conversely, a fat molecule can be formed by adding 3 fatty acid molecules to 1 glycerol molecule, removing 3 molecules of water

A(2): Groups of Fats

FatsFats

Unsaturated FatsUnsaturated FatsSaturated FatsSaturated Fats

A(2):

• Found mostly in animals• Fatty acids are straight chains

• Most are solid at room temperature (e.g butter)

• Cholesterol usually found with polysaturated fats Increases risk of Coronary Heart Diseases & Gall stone formation

Saturated FatsSaturated Fats

• Found mostly in vegetables (except Coconut and Palm Oil)

• Fatty acids are bent in some places

• Most are liquid at room temperature (e.g Olive Oil)

• Fatty acid chains contains double bonds and are able to take in 1 or more pairs of H-atoms

• Hydrogenation of unsaturated fats Trans-fat

A(1): Unsaturated FatsUnsaturated Fats

Saturated Fats Unsaturated Fats

Butter Cheese Fatty Meats Coconut oil Palm oil

Peanuts Walnuts Olives Corn Oil Soybean Most fishes (e.g Salmon,

mackerel, tuna, sardines)

A(2): Sources of Fats

A(1): Functions Fatsa) as a source and store of energy

b) Insulating material (Prevents excessive heat loss)

e.g layer of blubber beneath the skin of whales

c) Solvent for fat-soluble substances

some vitamins and vital substances (e.g hormones)

d) Essential part of the protoplasm e.g cell membrane (Phospholipds and cholesterol)

e) A way to reduce water loss from the skin surface

Food Test (3) Food Test (3) Test for Fats – Alcohol Test for Fats – Alcohol

Emulsion TestEmulsion Test

Procedure: Add 2 cm3 of ethanol to the test solution and

shake the mixture thoroughly for 5 minutes. Observe for changes.

Add 2 cm3 of water to the mixture and shake the mixture. Observe for changes.

Liquid Food

Food Test (3) Food Test (3) Test for Fats – Alcohol Test for Fats – Alcohol

Emulsion TestEmulsion Test

Procedure: Cut the sample into small pieces and place

them in a test tube. Add 2cm3 of ethanol and shake thoroughly. Allow the solid particles to settle. Decant the

ethanol into another test tube containing 2cm3 of water. Make observations.

Solid Food

Food Test (3) Food Test (3) Test for Fats – Alcohol Test for Fats – Alcohol

Emulsion TestEmulsion Test

Results: A white emulsion is formed if fats is present

white emulsio

n

Topic 3: Chapter 4

Nutrients Nutrients – – Part 3Part 3

ProProteintein

ss

Where are Proteins found in our body?

A(3): Proteins• Are very large complex organic moluecules

containing carbon (C), hydrogen (H), oxygen (O) and nitrogen (N). Sometimes, Sulfur (S) and Phosphorus (P)

• E.g. Insulin: C254H317O75N65S6

• Made up of basic small units called amino acids

ProteinsProteins

Acidic Group-COOH

Acidic Group-COOH

Formed from

Formed from

R-Groups:May contain:

Sulphur, Acidic groups,

amino groups, and/orHydroxyl groups

R-Groups:May contain:

Sulphur, Acidic groups,

amino groups, and/orHydroxyl groups

Amino Group-NH2

Amino Group-NH2

Amino AcidsNH2-CHR-COOH

Amino AcidsNH2-CHR-COOH

A(3): General Structure of an amino acid

• A fat molecule is made up of four parts:

- 1 Amino Acid group (-NH2)

- 1 Acidic Group (-COOH)

- 1 Side Chain (denoted by R)

Can be:•Sulfur (S)•Acidic groups (-COOH)•Amino groups (--NH2) and/or•Hydroxyl groups (-OH)

A(3): Why is there a need for so many different R-groups?

• The R-Group determines the type of amino acid formed.

• There are 20 naturally occuring amino acid:• Examples –

• Leucine, Valine, Glutamine:

• 8 Essential a.a: Cannot be synthesized by the body. Must be obtained through the diet

• 12 Non-Essential a.a: Can be synthesized by the body

A(3): Synthesis of Proteins

• The bond between 2 amino acids is called: Peptide Bond• Many amino acids link together by peptide bonds to form a

polypeptide chain / peptone

Condensation

Condensation

amino acids polypeptides Protein molecule

A(3): Synthesis of ProteinsPrimary / Secondary

StructurePrimary / Secondary

StructureTertiary StructureTertiary Structure

Amino acids are linked by

peptide bonds to form

polypeptide chains

Amino acids are linked by

peptide bonds to form

polypeptide chains

Polypeptide chains coil and

fold around each other to form a

3-d structure held by weak

H-bonds

Polypeptide chains coil and

fold around each other to form a

3-d structure held by weak

H-bonds

Different proteins have a different sequence of A.A

A.A sequence determines the bonds formed and the structure of the protein.

Different proteins with different structures perform different functions.

Weak H-bonds can be easily broken by:

• Heat• Chemicals like Acid and AlkalisProtein loses its structure

and function (is

DENATURED)

Different proteins have a different sequence of A.A

A.A sequence determines the bonds formed and the structure of the protein.

Different proteins with different structures perform different functions.

Weak H-bonds can be easily broken by:

• Heat• Chemicals like Acid and AlkalisProtein loses its structure

and function (is

DENATURED)

Structure VS FunctionStructure VS Function

A(3): Digestion of Proteins

polypeptides

amino acids

protein

hydrolysis (digestion)

hydrolysis (digestion)

Protein molecules are too large to pass through the cell membranes

Smaller and simpler A.A molecules are soluble in water and can pass through the cell membrane into the cells to synthesize new proteins

Animals Plants

Milk Eggs Seafood Chicken Lean beef

Nuts Soy bean Grains Vegetables

A(3): Sources of Proteins

A(1): Functions Proteins

a) Formation of new protoplasm

for growth & repair of worn-out body parts/ cells

b) Synthesis of enzymes and hormones e.g digestive enzymes and insulin / sex and

growth hormones

c) Formation of antibodies to combat diseases

d) Can be source of energy

Food Test (4) Food Test (4) Test for Proteins – Biuret Test for Proteins – Biuret

TestTest

Procedure: Add 1 cm3 of sodium hydroxide solution to the

2 cm3 of test solution. Shake thoroughly. Add 1% copper (II) sulphate solution, drop by

drop, shaking after each drop.

ALTERNATIVELY Add 2cm3 of test solution to an equal volume

of Biuret solution. Shake well and allow the mixture to stand for 5 minutes.

Food Test (4) Food Test (4) Test for Proteins – Biuret Test for Proteins – Biuret

TestTest

Results: A violet colouration is

formed if proteins is present

positive test for protein

positive test for protein