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Enzymes

We couldn’t live with out them!

Intermediate 2

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What is an enzyme?

• Known as a BIOLOGICAL CATALYST

• Catalyst is something that speeds up a chemical reaction

• Biological catalyst speeds up reactions in living cells

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Activation Energy

• Do this by lowering the ACTIVATION ENERGY - the energy required for a reaction to begin

Progress of reaction

En

erg

y

Uncatalysed reaction

Catalysed reaction

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Properties of Enzymes

• They are made of PROTEIN

• They are not changed by the reactions they speed up

• They are SPECIFIC- means that only one particular enzyme will work with one particular substrate

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Other terms you need to know

• Substrate – the substance that the enzyme works on e.g. Amylase the substrate is starch

• Product – the substance that is made by the reaction e.g. Breakdown of starch by Amylase the product is Maltose

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CATALASE

• Found in animal and plant cells

• Needed to speed up the breakdown of HYDROGEN PEROXIDE

• Breaks it down to OXYGEN and WATER

• The word equation for this looks like this

HYDROGEN PEROXIDE

CATALASE

OXYGEN AND WATER

HPCOW

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Amylase

• Found in saliva and in the pancreas

• Break down enzyme

• Breaks STARCH down to MALTOSE

• Word equation looks like this

STARCH MALTOSE

AMYLASESAM

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Potato Phosphorylase

• Synthesis enzyme (builds up)

• Builds Glucose-1-Phosphate molecules into Starch

• The formation of starch is tested using iodine solution

Phosphorylase

G1PPS

Glucose-1-Phosphate Starch

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More about Specific

• This means amylase will only breakdown starch

• Catalase will only breakdown hydrogen peroxide

• Amylase will NOT breakdown hydrogen peroxide

• Catalase will NOT breakdown starch

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Lock and Key

• All enzymes have a special shaped area that fits onto their substrate

• This area is called the ACTIVE SITE

• This Active site will fit onto the substrate while the reaction takes place

• Because it fits like a lock and key we call this the lock and key mechanism

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Model of Lock and Key

productssubstrate

enzyme enzyme – unchangedactive site

enzyme substrate complex

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Effect of Temperature

• Speed of reaction increases until an Optimum temperature is reached

• Optimum temperature is the temperature at which the enzyme works best

• After this point the rate of reaction decreases until there is no reaction

• At this point enzyme is said to be DENATURED – active site destroyed

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Effect of pH

• Most enzymes have an optimum pH of 7

• Some enzymes have a different optimum pH for example pepsin has an optimum pH of 2

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More to do

• Click on links to go to website and do Biology keystage 3 lessons 14,15,16,39 and 40

http://lgfl.skoool.co.uk/keystage3

• Also go to BBC bitesize standard grade biology topic investigating cells Enzymes and Aerobic Respiration

http://www.bbc.co.uk/scotland/education/bitesize/