Enzymes 2011 - Life Science Classroom
Enzymes 2011 - Life Science Classroom
Factors Affecting Enzyme Action
ENZYMES (CHEMICAL DIGESTION)
Large particles cannot be absorbed
in the small intestine
(e.g. starch) are
left in the gut
through into the
BUT large particles can
be broken down into
small particles. This is
Digestive enzymes speed up the process of
hydrolysis. Enzymes are biological catalysts.
All enzymes are protein in nature.
They are ORGANIC CATALYSTS that
chemical reactions without being used up in the
This means they remain unchanged by the
reaction and can be used OVER
OVER A small amount of enzyme can
catalyse a _________________
processing a lot of substrate.
An enzyme is very specific to the substrate upon
which it acts, e.g. The enzyme sucrase will only act
upon sucrose to form glucose + fructose (the
products). It will not act on any other substrate.
REVERSIBLE - they
Enzyme reactions are ________________
work in both directions.
They work very rapidly. Enzymes
TEMPERATURE changes in these
are sensitive to high ____________
Enzymes are sensitive to _________
ENZYMES LOWER THE AMOUNT OF ACTIVATION ENERGY NEEDED
FOR A CHEMICAL REACTION TO TAKE PLACE AND CAUSE A
REACTION TO OCCUR AT A RATE FAST ENOUGH TO BE
BIOLOGICALLY EFFICIENT WITHOUT HAVING TO ADD HEAT.
The activation energy
which is required to
hydrolyse sucrose into
its monomers during
digestion is indicated
in the following graph
Which curve represents the activation energy for this
reaction to take place when the required enzyme is added?
Provide a reason for your
C – LOWERS AMOUNT OF FREE ENERGY
NEEDED AND SPEEDS UP THE REACTION
LOCK AND KEY HYPOTHESIS
The shape of enzyme is critical - it must fit exactly into the
shape of the substrate molecule to
cause the reaction. This is why denaturing is so harmful.
This shape on the surface of the enzyme is called the
When the substrate and enzyme have locked together, this
TEMPORARY ENZYME-SUBSTRATE COMPLEX
After the reaction, it becomes an
thereafter they separate and the enzyme moves to the next
LOCK AND KEY MODEL
Active site: complimentary to the shape of the substrate
P + Q = SUBSTRATE
ENZYME-SUBSTRATE COMPLEX N = ENZYME
M = PRODUCT
Which letter represents the enzyme? Give ONE reason for your
– contains complimentary active site for substrates
Name two factors that can influence the above reaction.
Which one of the following (X, Y or Z) can be represented by the
condensation of two glucose molecules to form sucrose.
hydrolysis of sucrose to form glucose and fructose
condensation of two different amino acids to form a
Explain why the other two alternatives are not correct.
X – THE SUBSTRATE MOLECULES ARE DIFFERENT
AND 2 GLUCOSE WILL BE IDENTICAL
Y – THIS IS NOT AN HYDROLYSIS WHERE THE
SUBSTRATE IS BROKEN DOWN. IT IS A
The effect of temperaturechange and enzyme activity:
The particular temperature at which an enzyme acts
best is known as its
This temperature is ____________
At temperatures lower than the optimum, the enzyme
because they lack
As temperature increases up to the optimum
temperature, the enzyme activity
and then stops as the enzyme
A denatured enzyme loses its shape and hence its
pH- the amount of
ions in a solution.
Whatchyall lookin at bra ?
fewer H+1 ions.
extra OH+1 ions.
The effect of pH change on enzyme activity:
Enzymes work: at their best at a specific pH
called the ____________________
pH changes in BOTH directions away from the
optimum pH cause the enzyme to become
_______________________ - the
is damaged and
can no longer fit the substrate, so it cannot
Some enzymes can only 'work in the presence of a cofactor. A co-enzyme is an organic, non-protein co-factor
that works with the enzyme. "They usually transfer
chemical groups from one enzyme reaction to the next,
such as carrying hydrogen atoms during cell respiration.
is a co-enzyme during cell respiration,
so it is critical for optimal energy release from food that
we take in enough of it, or take supplements during
times of stress.
The enzyme in a
Catalase enzyme in potato acts on Hydrogen peroxide
Catalase enzyme in potato
Hydrogen gas + Oxygen gas
What’s going on?
1. Catalase decomposes hydrogen peroxide into …
What is the effect of pepsin on egg-white?
DIGESTS PROTEINS INTO POLYPEPTIDES
In which test tube/s will there be a result? TT3
Give a reason for your answer.
HCl (ACID), EGG WHITE (SUBSTRATE) AND PEPSIN (ENZYME)
Explain why there will not be result in the other test tube/s (if
there are any).
1 – NO HCl; 2 – NO ENZYME, 4 – ENZYME DENATURED BY BOILING
What result will be observed?
IN TT 3 – PIECES OF EGG WHITE DISAPPEAR AND A CLOUDY (3)
SOLUTION RESULTS, AS PROTEIN IS DIGESTED
Name the alcohol produced in the making of wine.
In which starchy product is the same alcohol formed,
but lost during the baking process?
2 Why is it not possible for natural fermentation to
increase the alcohol content of a fermented product to
20% or more?
YEAST DIES WHEN IT REACHES 18%
3 Name the enzyme used in making soft-centred
4 Name three dairy products made using enzymes.
CHEESE, MILK, YOGHURT ___________
Why is rennin/rennet used in cheese
It coagulates/clots milk
6 Why is it necessary to denature whey proteins when making yoghurt
IT MAKES THEM CREAMIER
7 Which enzymes are used to give jeans a “stone-washed” look?
Why is it better to use enzymes than real stones in the above case?
Give two reasons.
ECONOMIC: ENZYMES MORE EASILY SOURCED.
FASHION: DOES NOT DAMAGE JEANS
State one specific use of the enzyme ‘isomerase’.
GLUCOSE INTO FRUCTOSE
Why does the use of this enzyme make sense here?
FRUCTOSE SWEETER, LESS NEEDED, USED IN SLMMNG
9 What is pectin? POLYSACCHARIDE FOUND IN MIDDLE LAMELLA
10 Suggest why pectinase can make fruit juice clearer. (2)
BREAKS DOWN THE PECTIN AND REMOVES THE PULP
11.2 Name the enzyme, which was effective in this
11.3 What was found to be the most suitable temperature for
the action of this enzyme?
11.4 What indicator would you have used to show the
presence of starch?
11.5 How long would you expect digestion to have taken place
in a similar test conducted at 22,5 0C? (Indicate how
you found this on the graph)
11.6 Name the end-product of the digestion of
the cooked starch.
11.7 Name TWO other factors affecting enzyme
efficiency which could be tested by similar
AMOUNT OF SUBSTRATE or
AMOUNT OF ENZYME