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