Proteins Proteins The Building Blocks of our BodyThe Building Blocks of our Body

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Elemental CompositionElemental CompositionProteins are made up of atoms of:Proteins are made up of atoms of:

Carbon Carbon CCHydrogenHydrogen HHOxygenOxygen OONitrogenNitrogen NN and sometimes Phosphorus (P), Sulphur (S) and and sometimes Phosphorus (P), Sulphur (S) and Iron (Fe)Iron (Fe)Nitrogen is needed for growth.Nitrogen is needed for growth.Proteins are the only nutrients that contain the Proteins are the only nutrients that contain the element nitrogen.element nitrogen.These elements are bonded together in small These elements are bonded together in small molecules called amino acids.molecules called amino acids.Amino acids are bonded together into long chains Amino acids are bonded together into long chains called proteinscalled proteins

Basic Structure of proteins – Basic Structure of proteins – Amino AcidsAmino Acids

Proteins are made up of Proteins are made up of chains of small molecules chains of small molecules called amino acids.called amino acids.There are 20 different There are 20 different amino acids but each has amino acids but each has the same basic structure.the same basic structure.C = carbon atomC = carbon atomH= Hydrogen atomH= Hydrogen atom

NNHH2 2 = Amino group (basic)= Amino group (basic)COOH = Carboxyl group COOH = Carboxyl group (acidic)(acidic)R = Variable group, R = Variable group, changes for every aminochanges for every aminoFor example in the amino For example in the amino acid Glycine the R group = acid Glycine the R group = H (one Hydrogen Atom)H (one Hydrogen Atom)

Essential Amino AcidsEssential Amino Acids

There are over 20 different amino acids.There are over 20 different amino acids.

8 are 8 are Essential Amino AcidsEssential Amino Acids that cannot be that cannot be made by the body and must be eaten.made by the body and must be eaten.

There are 2 extra essential amino acids for There are 2 extra essential amino acids for children.children.

The rest are The rest are Non-Essential Amino Acids Non-Essential Amino Acids these these can be made by the bodycan be made by the body

Essential and Nonessential Essential and Nonessential Amino AcidsAmino Acids

Essential Amino acids cannot be made by the body Essential Amino acids cannot be made by the body and must be obtained from foodand must be obtained from food

VVincent’s incent’s

LLovely ovely

MMotherother

TTookook

HHimim

TToo

LLondonondon

IIn n

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PPramram

Valine

Lysine

Methionine

Trytophan

Histidine (children)

Threonine

Leucine

Isoleucine

Arginine (children)

Phenylalnine8 essential for adults and 10 for children

Peptide Bonds or LinksPeptide Bonds or LinksAmino acids join together into long chains called Amino acids join together into long chains called proteins.proteins.Just like the 26 letters of the alphabet can form Just like the 26 letters of the alphabet can form thousands of words by linking in different ways; the thousands of words by linking in different ways; the 20 amino acids can form many different proteins20 amino acids can form many different proteinsThe bond that links one amino acid to another is The bond that links one amino acid to another is called a peptide link or bondcalled a peptide link or bondEach time 2 amino acids link together a water Each time 2 amino acids link together a water molecule is taken away and so the linking process is molecule is taken away and so the linking process is called called CondensationCondensation..The reverse of condensation is called The reverse of condensation is called HydrolysisHydrolysis, , water molecules are added to protein chains and split water molecules are added to protein chains and split the amino acids apart, this happens during protein the amino acids apart, this happens during protein digestion.digestion.

Peptide Bonds or LinksPeptide Bonds or LinksThe Amino group (NH2) of one amino acid links The Amino group (NH2) of one amino acid links with the Carboxyl group (COOH) of another amino with the Carboxyl group (COOH) of another amino acid.acid.The Amino group (NH2) looses one H, the The Amino group (NH2) looses one H, the Carboxyl group (COOH) looses an OH group.Carboxyl group (COOH) looses an OH group.The H and OH bond together to form a water The H and OH bond together to form a water molecule (H2O)molecule (H2O)The remaining CO and NH bond together to form The remaining CO and NH bond together to form a peptide link.a peptide link.Two amino acids joined is called a Two amino acids joined is called a DipeptideDipeptideMany amino acids joined in a chain is called a Many amino acids joined in a chain is called a PolypeptidePolypeptide

Amino Acids Bonding to form Amino Acids Bonding to form proteinprotein

Protein structure - PrimaryProtein structure - Primary

Order and Order and number of number of amino acids in a amino acids in a protein chain protein chain for example the for example the protein insulin protein insulin has over 50 has over 50 amino acids in amino acids in its chain its chain arranged in a arranged in a definite order.definite order.

Protein structure Protein structure - Secondary- Secondary

Involves the folding of the Involves the folding of the protein chain into a spiral protein chain into a spiral or zig-zag shapeor zig-zag shapeThis structure is caused by This structure is caused by crosslinks that form crosslinks that form between different chains between different chains or within the one chain. or within the one chain. There are different types There are different types of cross-linksof cross-links(a) (a) Disulfide linksDisulfide links which which happen when 2 Sulphur happen when 2 Sulphur atoms bond .atoms bond .(b) (b) Hydrogen bondsHydrogen bonds where where a Hydrogen atom in one a Hydrogen atom in one chain bonds with an chain bonds with an Oxygen atom in another Oxygen atom in another chain.chain.

Protein structure - TertiaryProtein structure - TertiaryThis refers to the 3 dimensional This refers to the 3 dimensional folding of the chain. This structure folding of the chain. This structure can be globular or fibrous. The can be globular or fibrous. The shapes give certain properties to shapes give certain properties to the proteinthe proteinGlobularGlobular : In these the protein : In these the protein chain is rolled up like a ball of chain is rolled up like a ball of wool. This structure makes the wool. This structure makes the protein soluble. This type of protein soluble. This type of protein is found in body cells, protein is found in body cells, myoglobin in meat, albumin in myoglobin in meat, albumin in egg, haemoglobin in blood.egg, haemoglobin in blood.FibrousFibrous: In these the protein chain : In these the protein chain takes on a straight, coiled or zig-takes on a straight, coiled or zig-zag shape. These shapes make zag shape. These shapes make the protein insoluble and stretchy the protein insoluble and stretchy or tough. Gluten in wheat and or tough. Gluten in wheat and elastin in meat have a coiled elastin in meat have a coiled structure. Collagen in meat has a structure. Collagen in meat has a zig-zag structure.zig-zag structure.

Sources of proteinSources of protein

Animal protein Animal protein Plant proteinPlant protein

CheeseCheese Soya beansSoya beans

ChickenChicken TVPTVP

MeatMeat NutsNuts

FishFish LentilsLentils

EggsEggs PeasPeas

MilkMilk BeansBeans

CerealCereal

PROTEIN CLASSIFICATIONPROTEIN CLASSIFICATION

SIMPLE SIMPLE CONJUGATEDCONJUGATED DERIVEDDERIVED These proteins are formed due These proteins are formed due

to a chemical or enzyme action on a to a chemical or enzyme action on a

protein : i.e: Rennin acts on protein : i.e: Rennin acts on

caesinogen and makes caesin caesinogen and makes caesin

PROTEIN + NON-PROTEINPROTEIN + NON-PROTEIN Protein + Lipid = Protein + Lipid = LipoproteinLipoprotein (lecithin) (lecithin)

Protein + Phosphate = Protein + Phosphate = PhosphoproteinPhosphoprotein (caesin) (caesin)

Protein + nucleic acid = Protein + nucleic acid = NucleoproteinNucleoprotein (DNA) (DNA)

Protein + Colour Pigment = Protein + Colour Pigment = ChromoproteinChromoprotein (Haemoglobin) (Haemoglobin)

ANIMAL ANIMAL PLANTPLANTClassified Classified ClassifiedClassified GLUTENINS GLUTENINS : Soluble in acids & alkali: Soluble in acids & alkali

according according accordingaccording Glutenin in wheat Glutenin in wheat

to shapeto shape to solubilityto solubility

PROLAMINESPROLAMINES: Soluble in alcohol: Soluble in alcohol

FIBROUSFIBROUS GLOBULAR gliadin in wheat GLOBULAR gliadin in wheat

CollagenCollagen albumin albumin

Properties of protein – effects Properties of protein – effects of heat on proteinof heat on protein

Effect of heatEffect of heat ExamplesExamplesCoagulation: protein sets Coagulation: protein sets and then hardensand then hardens

Hard boiling eggsHard boiling eggs

Colour changeColour change Myoglobin in meat - red Myoglobin in meat - red to brownto brown

Maillards reaction (dry Maillards reaction (dry heat)heat)

Bread crustBread crust

Tenderising (moist heat)Tenderising (moist heat) Collagen in meat Collagen in meat changes to gelatine and changes to gelatine and fibres fall apartfibres fall apart

Becomes indigestibleBecomes indigestible Overcooked meat or Overcooked meat or cheese becomes tough cheese becomes tough and hard to digestand hard to digest

1.1. DenaturationDenaturation

Denaturation is a change in the Denaturation is a change in the nature of the proteinnature of the protein

The protein chain unfolds, causing The protein chain unfolds, causing a change to the structurea change to the structure

Denaturation is caused by a) heat, Denaturation is caused by a) heat, b) chemicals and b) chemicals and

c) agitationc) agitation

It is often an irreversible processIt is often an irreversible process

A.A. HeatHeat

Most proteins coagulate/set when Most proteins coagulate/set when heated.heated.

E.g. Egg white coagulates at 60˚C; E.g. Egg white coagulates at 60˚C; egg yolk coagulates in the egg yolk coagulates in the stomach at 68˚Cstomach at 68˚C

B.B. ChemicalsChemicals

Acids, alkali, alcohol & enzymes Acids, alkali, alcohol & enzymes cause changes to the protein cause changes to the protein structurestructure

E.g. Lemon juice added to milk E.g. Lemon juice added to milk causes the milk protein caesinogen causes the milk protein caesinogen to curdleto curdle

E.g. Enzyme rennin coagulates milk E.g. Enzyme rennin coagulates milk protein caesinogen in the stomachprotein caesinogen in the stomach

C.C. AgitationAgitation

This is also known as mechanical This is also known as mechanical actionaction

It involves whipping or whisking the It involves whipping or whisking the proteinprotein

This results in the protein chain This results in the protein chain unfolding & partial coagulationunfolding & partial coagulation

Properties of ProteinProperties of Protein

4.4. ElasticityElasticityCertain proteins have an Certain proteins have an elastic property, e.g. Gluten, elastic property, e.g. Gluten, the protein found in flour, the protein found in flour, enables bread to rise during enables bread to rise during cookingcooking

5.5. Foam FormationFoam FormationWhen egg white is whisked, When egg white is whisked, air bubbles are formed as air bubbles are formed as the protein chains unravelthe protein chains unravelWhisking also produces Whisking also produces heat, which slightly sets the heat, which slightly sets the egg whiteegg whiteThis foam will collapse after This foam will collapse after a while, unless it is a while, unless it is subjected to heatsubjected to heatThis property is used to This property is used to make meringuesmake meringues

Properties of Protein of Protein

Properties of ProteinProperties of Protein6.6. Gel formationGel formation

Collagen, when heated, Collagen, when heated, forms gelatineforms gelatine

Gelatine can absorb large Gelatine can absorb large amounts of water and, amounts of water and, when heated, forms a solwhen heated, forms a sol

On cooling, this becomes On cooling, this becomes solid & a gel is formedsolid & a gel is formed

A gel is a semi-solid viscous A gel is a semi-solid viscous solutionsolution

All gels have a three-All gels have a three-dimensional network dimensional network whereby water becomes whereby water becomes trapped. This property is trapped. This property is used in making used in making cheesecakes and souffléscheesecakes and soufflés

Gelatine Gelatine

Heat is appliedHeat is applied

As the proteinAs the proteinUncoils water Uncoils water

becomes trappedbecomes trapped SolSol

Pro gelPro gel

WaterWater

Protein Matrix – the mixture has set – it Protein Matrix – the mixture has set – it has become a gelhas become a gel

Biological Functions of ProteinBiological Functions of ProteinFunction typeFunction type FunctionFunction Result of deficiencyResult of deficiency

Structural Structural FunctionFunction

Growth & repair Growth & repair of body cells of body cells muscles &skinmuscles &skin

Retarded Retarded growthgrowth

Delayed healingDelayed healing

Physiologically Physiologically active proteinactive protein

Making Making hormones, hormones, enzymes, enzymes, antibodies, antibodies, blood protein, blood protein, nucleoproteinnucleoprotein

Body organs & Body organs & systems systems malfunction. malfunction. Easily infected.Easily infected.

Nutritive ProteinNutritive Protein Provides Provides essential amino essential amino acids for the acids for the body.body.

Excess protein Excess protein used for energyused for energy

Lack of Lack of energy.energy.

Kwashiorkor, Kwashiorkor, MarasmusMarasmus

DeaminationDeamination

This is the process by This is the process by which excess protein is which excess protein is used for energy.used for energy.Left over amino acids Left over amino acids are brought to the are brought to the liverliverThe The NHNH22 group group is is broken off, changed to broken off, changed to ammonia, then to urea ammonia, then to urea and then excreted.and then excreted.The rest of the The rest of the molecule is converted molecule is converted to glucose and used for to glucose and used for releasing energy.releasing energy.

Biological Value of ProteinBiological Value of ProteinThe Biological Value of a protein is a measure of the The Biological Value of a protein is a measure of the quality of the protein and is expressed as a %.quality of the protein and is expressed as a %.

It is decided by the number of essential amino acids It is decided by the number of essential amino acids a protein contains in proportion to how much of them a protein contains in proportion to how much of them the body needs.the body needs.

There are 2 types of protein foods:There are 2 types of protein foods:

(a) (a) High Biological valueHigh Biological value, contain all essential Amino , contain all essential Amino Acids, complete proteins, animal sources.Acids, complete proteins, animal sources.

(b) (b) Low Biological value,Low Biological value, lack some essential amino lack some essential amino acids, incomplete protein, plant sourcesacids, incomplete protein, plant sources

Biological Value of different Biological Value of different proteinsproteins

SourceSource FoodFood HBVHBV LBVLBV ProteinProtein

AnimalAnimal EggsEggs 100%100% Ovalbumin, Livetin, VitelinOvalbumin, Livetin, Vitelin

MilkMilk 95%95% Casein, Lactalbumin, Casein, Lactalbumin, LactoglobulinLactoglobulin

MeatMeat 80-80-90%90%

Collegen, Elastin, Myosin,Collegen, Elastin, Myosin,

FishFish Actin, Myosin, CollegenActin, Myosin, Collegen

GelatineGelatine 0%0% GelatineGelatine

PlantPlant Soya Soya BeansBeans

74%74%

RiceRice 6767%%

OryzeninOryzenin

WheatWheat 5353%%

GlutenGluten

MaizeMaize 4040%%

ZeinZein

Supplementary Value of ProteinSupplementary Value of ProteinWhen low biological value foods, that When low biological value foods, that lack essential amino acids, are eaten lack essential amino acids, are eaten together they can provide all the together they can provide all the essential amino acid. essential amino acid. The essential amino acids missing in The essential amino acids missing in one food can be made up for by being one food can be made up for by being present in the other food and visa present in the other food and visa versa.versa.This complementary value of protein This complementary value of protein means that vegans can get all the means that vegans can get all the essential amino acids without eating essential amino acids without eating animal foodanimal foodExample; Bread is lacking Lysine but is Example; Bread is lacking Lysine but is high in Methionine. Beans are lacking high in Methionine. Beans are lacking Methionine but high in Lysine. By Methionine but high in Lysine. By eating beans on toast both essential eating beans on toast both essential amino acids are included in the meal.amino acids are included in the meal.

RDA Protein & Energy valueRDA Protein & Energy value

RDARDA

1gram of protein per kilogram of body weight.1gram of protein per kilogram of body weight.

Child 30-50g/dayChild 30-50g/day

Teenager 60-80g/dayTeenager 60-80g/day

Adults 50-75g/dayAdults 50-75g/day

Pregnant or lactating 70-85g/dayPregnant or lactating 70-85g/day

Energy ValueEnergy Value

1g of protein gives 4kCal or 17 kJ energy1g of protein gives 4kCal or 17 kJ energy

Digestion of proteinDigestion of protein

Part of Part of SystemSystem

PhysicalPhysical

DigestionDigestion

Digestive Digestive JuiceJuice

EnzymeEnzyme SubstrateSubstrate ProductProduct

MouthMouth ChewedChewed

StomachStomach ChurnedChurned GastricGastric

juicejuice

RenninRennin

PepsinPepsin

CaseinogenCaseinogen

ProteinsProteins

CaseinCasein

PeptonesPeptones

DuodenumDuodenum Pancreatic Pancreatic

JuiceJuice

TrypsinTrypsin ProteinProtein PeptonesPeptones

Small Small IntestineIntestine

Intestinal Intestinal JuiceJuice

PeptidasePeptidase PeptonesPeptones Amino acidsAmino acids

Absorption & Assimilation of Absorption & Assimilation of Amino AcidsAmino Acids

Amino Acids are absorbed into blood capillaries in Amino Acids are absorbed into blood capillaries in the villi of the small intestine.the villi of the small intestine.

These capillaries connect into the portal vein These capillaries connect into the portal vein which carries the amino acids to the Liver.which carries the amino acids to the Liver.

From here the Amino Acids will be sent to (a) From here the Amino Acids will be sent to (a) replace & repair body cells, (b) form new cells, replace & repair body cells, (b) form new cells, antibodies, hormones, enzymes or (c) be antibodies, hormones, enzymes or (c) be deaminateddeaminated

Questions??Questions??1 What is the elemental composition of protein?1 What is the elemental composition of protein?

2 Draw the chemical structure of an amino acid2 Draw the chemical structure of an amino acid

3 Explain how a peptide link forms3 Explain how a peptide link forms

4 What are essential amino acids?4 What are essential amino acids?

5 List the biological functions of protein.5 List the biological functions of protein.

6 What is meant by ‘biological value’ of protein?6 What is meant by ‘biological value’ of protein?

7 Difference between denaturation & deamination 7 Difference between denaturation & deamination

8 List (a) the energy value (b) the RDA of protein?8 List (a) the energy value (b) the RDA of protein?

9 List 4 sources of (a) HBV and (b) LBV protein.9 List 4 sources of (a) HBV and (b) LBV protein.

10 Describe the digestion of protein in humans.10 Describe the digestion of protein in humans.