B2_1.26_Enzymes as biological catalystsB2_1.27_Enzymes catalyse chemical reactions – e.d DNA replication, Protein Synthesis, Digestion. B2_1.28_Factors affecting enzyme actionB2_1.29_Enzymes are highly specific for their substrateB2_1.30_Lock-and-key hypothesisB2_1.31_Enzymes can be denaturedB3_3.10_Enzyme technologyB3_3.12_Enzymes in food production

Practical work we will do during the practical weeks

B2_1.32_Factors that affect enzyme activityB3_3.11 Investigate the use of immobilised lactase /

B3_3.12_Enzymes in food production

Last week we talked about how proteins are made… so what are Proteins? Protein (from the Greek word “proteios” meaning 1st place

Proteins account for more than 50% of the dry weight of cells –and are VITAL in almost everything organisms do!

Organic molecules Containing

C, H, O and N

PROTEINS!

Defense

Structural support Storage

Transport

Signaling

Movement

Proteins have many vital functions, including…

Additionally as ENZYMES proteins regulate metabolism by regulating chemical reactions in the cell.

Humans have tens of thousands of different proteins… each with a different, specific structure & function!

HORMONES

e.g’s Globular proteins

ENZYMES ANTIBODIES

e.g’s Fibrous proteins

Keratin Collagen

So, Proteins have a variety of functions:

(i.e. enzymes hydrolyze large food molecules:– digestive enzymes) others help make (synthesize) large molecules.

Enzymes: usually globular, due to tight folding and coiling of polypeptide chains. They are often soluble and are

important in metabolism…

B2_1.26_Enzymes as biological catalystsB2_1.27_Enzymes catalyse chemical reactionsB2_1.29_Enzymes are highly specific for their substrateB2_1.30_Lock-and-key hypothesis

So, Enzymes are proteins.

They are very important substances becausethey control the chemical reactions thathappen in our bodies…

Enzymes are known as biologicalcatalysts - substances which speedup reactions but which do not getused up themselves.

Enzyme names usually end in the letters -ase, for example:amylase, protease and lipase.

Enzymes act as biological Catalyststo speed up chemical reactions

How does an enzyme actually catalyses a chemical reaction?

Enzymes catalyse a chemical reaction by combining with areactant and speeding up the reaction.

The reactant iscalled the substrate.

The enzyme has aspecific indentationcalled an active site,which helps it torecognise thatsubstrate.

Enzymes and Subrate “lock and Key” hypotheis…

There are two main types of enzymes 1) Those that break down

large molecules intosmaller ones. These arevery important indigestion, why?

They are required to break downlarge food molecules into smallerones that can be used by our cells 2) Those that build

up large molecules from small ones. These are very

important for growth and repair.

Enzyme specificity

Use the diagram (left) to help you

to explain why each enzyme will only catalyse one

particular reaction.

Substrate B

B2_1.28_Factors affecting enzyme action

B2_1.31_Enzymes can be denatured

• Temperature• pH• Concentration

Many factors affect how well enzymes

function: you need to know 3 of them…

Temperature & pH

Most enzymes function bestat normal Body temperature:37°CHigh temperatures willusually result in an enzymesdenaturationMost enzymes like nearneutral pH (6 to 8)Denaturation is defined as aperminant change in thetertiary (3-dimensional)structure of a proteinWhen an enzyme isdenatured it is no longer ableto function

1. The Effect of Temperature

Enzymes are proteins. At hightemperatures these proteins startto unravel. This changes the shapeof the active site and as a result thesubstrate can no longer fit into it.

When this happens the enzyme issaid to be ‘denatured’. Once anenzyme is denatured it will notwork.

As temperature increases the rate of reaction increases up to amaximum (usually around 40°C). After this point the rate ofreaction will decrease.

High temperatures will resultin enzyme denaturation.

1. Effect of temperature on enzyme action!

The rise in temperature makes the enzyme molecules vibrate

more…

If the temperature goes above a certain level, this vibration breaks some of the

bonds that hold the enzyme in shape

Thus, the active site changes shape and the

enzyme and substrate no longer fit together.

At this point, the enzyme is Denatured – it no longer functions as a catalyst.

2.TheEffectofpHEnzymes in the human body will work at an optimum within narrowpH ranges. pH changes beyond an enzymes optimum will result in theenzymes denaturation.

HowpHaffectsenzymeactivity

An enzymes catalytic activityis affected by how acidic oralkaline its environment is.

The majority of enzymeswork best in neutralconditions. However, someprefer acidic and othersprefer alkaline conditions.

If the active site of the enzyme is changed (i.e. it is denatured) then the substrate can no longer bond/attach to the active site of the enzyme. Therefore no reaction can take place and no product produced

Similar to temperature, the active site of an enzyme can be changed by conditions that are either too acidic or too alkaline.

2. How pH affects enzyme activity

3. Enzyme Concentration

The more enzyme in a solution, thegreater the chance that an enzymesubstrate complex will form, and thegreater the rate of reaction up to amaximum when all active sites arefully occupied.

Substrate ConcentrationThe more

substrate in the solution the greater the chance of a substrate

molecule finding an active site, and

the faster the rate of reaction

up to a maximum when all active sites are fully

used.

Q. Why do you think that the reaction goes faster as the

temperature increases? (think about what happens to molecules as they

warm up)

The molecules involved in the reaction will have more kinetic energy as the temperature increases, so they will move about more, collide more.

So the enzyme and substrate molecules are more likely to collide or combine with each other (and therefore react)

So… Enzymes lower the activation energy for a

reaction

FreeEnergy

Progressofthereaction

Reactants

Products

Freeenergyofactivation

WithoutEnzyme

WithEnzyme

B33.10Enzymetechnology&B33.12Enzymesinfoodproduction

Enzymes use in sweet

manufacturing How do you get the runny center inside a cream egg?

Tomakesoft centersinchocolatesmanymanufacturesaddanenzymecalledinvertase(sucrase)whichcatalysesthereactiontobreakthesugarsucrosedown.

ManyConfectionarysweetsaremadeusingenzymes– specificallyandenzymecalledInvertase(sucrase).Invertaseisproduced byyeastandwecanutilisethisenzyme.Invertase/sucrasebreaksdownsucroseintothemonosaccharides glucoseandfructose.

Many Confectionary sweets are made using enzymes – specifically and enzyme called Invertase (sucrase). Invertase is produced by yeast and we can utilise this enzyme.Invertase / sucrase breaks down sucrose into the monosaccharides glucose and fructose.

To make soft centers in chocolates many manufactures add an enzyme called invertase (sucrase) which catalyses the reaction to break the sugar sucrose down.

EnzymesusedinmakingVegetarian

Cheese

B33.10Enzymetechnology&B33.12Enzymesinfoodproduction

Chymosinwasorginally obtainedfromcalvesstomachtissues.Howevernow,theenzymeismadeusinggeneticallymodifiedbacteria.Theprocessismoreefficientandtheproduct(Chymosin)containslessimpuritiesandactsmorepredictably.

Enzymesincheesemaking.Cheeseismadewhentheenzymechymosin.Chymosinactsuponmilk– specificallytheenzymecatalysesreactionsthatcauseproteinsinmilk(curds)tocoagulateandseparatefromtheliquid(whey).

Enzymes using in Biological washing powdersBiological washing powders contain enzymes, for example:Proteases – break down proteins into amino acidsLipases – break down fats into glycerol and fatty acidsCarbohydrases (e.g. amylase) –break down sugars (polysaccahrides, e.g. starch) into monosaccahrides (e.g. glucose)

B33.10Enzymetechnology&B33.12Enzymesinfoodproduction

Because biological washing powders contain enzymes (biological catalysts) they work best at “optimal temperatures”.

Which means they are most effective at lower temperatures, e.g around 30OC. This has many other benefits:

• Less energy is used (heating water / production

of carbon emissions)• Dyes in fabrics are less

likely to ‘run’ out of fabrics

• Clothes are less likely to shrink in the wash.

Which means they are most effective at lower temperatures, e.g around 30OC. This has many other benefits:

• Less energy is used (heating water / production

of carbon emissions)• Dyes in fabrics are less

likely to ‘run’ out of fabrics

• Clothes are less likely to shrink in the wash.

Because biological washing powders contain enzymes

(biological catalysts) they work best at “optimal temperatures”.

Whenwerevisitenzymesinalittlemoredetailwhenweinvestigateenzymeaction:i.e.• Useofimmobilizedenzymes• Lactasewillbreakdownlactoseinmilk• Pectinasewillbreakdownpectin(asugar

foundinthecellwallsofplants/fruit)• InvestigatehowtemperatureandpH

effectenzymeaction

The digestive system – e.g. the Enzymes that break down carbohydrates (Carbohydrases like amylase found in the saliva in the mouth)

We will come across enzymes again when we go through…