investigating enzymes how an enzyme works enzymes in living cells proteinsall living cells. enzymes...

INVESTIGATING ENZYMES

How An Enzyme Works

Enzymes in living cells Enzymes are PROTEINSPROTEINS which are present in

ALL LIVING CELLS. ALL LIVING CELLS. They act as biological CATALYSTS by

SPEEDING UPSPEEDING UP chemical reactions without being used up itself.

Why do we need enzymes ?

most cells work at relatively low temperatures and their chemical reactions (e.g. respiration, digestion, photosynthesis) would be too slow to sustain life without the help of enzymes !

Uses of enzymes1) Enzymes are used in washing powders to help digest food stains. Biological washing powders will only work on 400C or lower.2) Enzymes are used in baby foods to “pre-digest” the proteins.

3) Enzymes are used to convert starch into sugar which can then be used in food.

Enzyme Specificity is

called the lock-key

hypothesis!!

ENZYME DESIGN The substance on which an enzyme acts

is called the SUBSTRATE The reaction happens when the ENZYME

molecule and the SUBSTRATE molecule are fitted together

Each ENZYME has to be shaped EXACTLY to suit its own substrate

Examples – Notice the “ase” ending

SUBSTRATE ENZYME

Urea Urease

Lipid Lipase

Lactose Lactase

Lactase only works with Lactose etc.

ACTIVATION ENERGY- the energy needed to start a chemical reaction

Enzymes lower the amount of activation energy needed!!

reactants

products

energybarrierwith no

enzyme topromotereaction

energybarrier

withan

enzyme’sparticipati

on

Activation Energy

Enzymes – How they work!

Enzymes

Protein Polymer

Lots of Smaller Amino-acids (monomers)

The concept of metabolism

Metabolism = all the chemical reactions taken place inside the living organisms

Metabolic reactions produce different life processes, e.g. – photosynthesis– respiration– movement– growth– reproduction

Control of metabolism

Metabolic reactions can be controlled and speeded up by enzymes– metabolic reactions would be too slow to

occur if no enzymes are present!

Catabolic/decomposition chemical reactions..

Involve the BREAKDOWN of big molecules into smaller ones (Hydrolysis)

Anabolic/synthesis chemical reactions.. BUILD UP smaller molecules into bigger

ones (Dehydration Synthesis)

Without enzymes, chemical reactionsin living cells would be far too slow!!

Temperature & Enzyme ActivityTemperature & Enzyme ActivityAll enzymes are made of PROTEINPROTEIN so are DENATUREDDENATURED at high temperatures (above about 50°C) .. think boiled eggs !!

The rate of enzyme activity increases with temperature up to a maximum (OPTIMUM OPTIMUM TEMPTEMP.) then falls to zero as the enzyme is denatured.

pH & Enzyme ActivitypH & Enzyme Activity

pHpH also affects the rate of enzyme activity. Each enzyme has its own range range of pHof pH in which it will work.

Examples :

the enzyme PEPSINPEPSIN only works between (pH 1-4)pH 1 - pH 4 (acidic)

the enzyme CATALASECATALASE only works between (pH 8-11)pH (alkaline)

OptimumOptimum = "the best” ... The enzyme is working at its very fastestvery fastest

More reaction facts… An example of a BREAKDOWN

reaction. The enzyme,AMYLASE breaks

down STARCH into MALTOSE An example of a SYNTHESIS

reaction... The enzyme PHOSPHORYLASE

builds up glucose(-1 phosphate) into STARCH.

BUT REMEMBER,EACH ENZYME CAN ONLYCATALYSE ONE REACTION.

DENATURATION

Enzymes are made of proteins Proteins are sensitive to external conditions

such a temperature, pH, salt levels etc If conditions change it can cause the active

site of an enzyme to change shape When this happens, the substrate can no

longer fit and the enzyme quits working

And finally... ‘Optimum’ is a

useful word which means ‘best’

So we call the TEMPERATURE and the pH which makes an ENZYME work at its very fastest, the OPTIMUM for that enzyme.

One More Time ……

Use the drawing to answer the question

Use the drawing to answer the question

Enzymes in the Digestive System

Cracker Lab – Exploring Amylase “Enzyme Madness”

Apple Experiment

Observe the two apple bites. What is different about them? Why?

An enzyme present in apples is called catecholase. When catechol and oxygen interact, the enzymatic reaction causes the apple to brown. The low pH of the lemon, however, stops this reaction.

“An Apple a Day ……”

Take a bite of an apple. On the opposite side of the apple take a second bite. Rub lemon juice on the second bite mark and set your apple aside.

Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction.

Enzymes are denatured

beyond 40OC

Enzymes work best in certain conditions:

Enzyme activity

Temp pH pH400C

Could be protease (found in the stomach)

Could be amylase (found in the intestine)

Enzymes vary in the pH and temperatures that make them work best!

In Your Journal write:

Name industries that use enzymes to improve their products.

How did the Egyptians use enzymes? Where was Rennin collected from in the

past? Discuss how large quantities of enzymes

are currently produced. Could we survive without enzymes?

The Following Video will provide the answers

HISTORY AND USE OF ENZYMES MOVIE