Enzymes 2011 - Life Science Classroom

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Transcript Enzymes 2011 - Life Science Classroom

ENZYMES
Enzymes
Enzyme Action
Factors Affecting Enzyme Action
1
ENZYMES (CHEMICAL DIGESTION)
Remember :
 Large particles cannot be absorbed
in the small intestine
Large particles
INSIDE THE
BODY (BLOOD)
GUT
starch
starch
G
starch
G
G
(e.g. starch) are
left in the gut
and small
particles (e.g.
glucose) go
through into the
blood.
G
G
G
starch
BUT large particles can
be broken down into
small particles. This is
called DIGESTION
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ENZYMES




Digestive enzymes speed up the process of
hydrolysis. Enzymes are biological catalysts.
All enzymes are protein in nature.
They are ORGANIC CATALYSTS that
SPEED UP
CONTROL
___________________
and _______________
chemical reactions without being used up in the
process.
This means they remain unchanged by the
reaction and can be used OVER
______ and
OVER A small amount of enzyme can
_________;
REACTION
catalyse a _________________
many times,
processing a lot of substrate.
3
ENZYMES
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.
Extreme
 They work very rapidly. Enzymes
TEMPERATURE changes in these
are sensitive to high ____________
cause
 Enzymes are sensitive to _________
pH
DENATURATION
_____________
changes.

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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
as X.
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
answer.______________________
NEEDED AND SPEEDS UP THE REACTION
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LOCK AND KEY HYPOTHESIS





The shape of enzyme is critical - it must fit exactly into the
COMPLIMENTARY
_____________________
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
ACTIVE SITE
______________________
When the substrate and enzyme have locked together, this
forms an
TEMPORARY ENZYME-SUBSTRATE COMPLEX
___________________________________________________
After the reaction, it becomes an
_______________________________________.
and
ENZYME-PRODUCT COMPLEX
thereafter they separate and the enzyme moves to the next
reaction.
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7
LOCK AND KEY MODEL
HYDROLYSIS
CONDENSATION
P
S
+
+
S
P
E
+
S
ES complex
E
+ P
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Active site: complimentary to the shape of the substrate
P + Q = SUBSTRATE
ENZYME-SUBSTRATE COMPLEX N = ENZYME
M = PRODUCT
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Which letter represents the enzyme? Give ONE reason for your
choice.
N_______________________________________________________
– contains complimentary active site for substrates
 Name two factors that can influence the above reaction.
TEMPERATURE
 _______________________________________________________
pH
 _______________________________________________________
 Which one of the following (X, Y or Z) can be represented by the
above reaction?
 X
condensation of two glucose molecules to form sucrose.
 Y
hydrolysis of sucrose to form glucose and fructose
 Z
condensation of two different amino acids to form a
Z
dipeptide.
________________
 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
CONDENSATION

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The effect of temperaturechange and enzyme activity:
11
The particular temperature at which an enzyme acts
best is known as its
__________________________________________.
OPTIMUM
TEMPERATURE
37,5OC
This temperature is ____________
 At temperatures lower than the optimum, the enzyme
INACTIVE
remains ________________
because they lack
ENERGY
_________________.
 As temperature increases up to the optimum
temperature, the enzyme activity
INCREASES
___________________
and then stops as the enzyme
DENATURING
starts ________________________.
 A denatured enzyme loses its shape and hence its
specifically shaped
ACTIVE SITE
_________________________________________.
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
+
H
pH- the amount of
ions in a solution.
Whatchyall lookin at bra ?
1
2
3
4
ACID
extra H+1
ions
(protons)
5
6
7
8
9
10
11
12
BASE
fewer H+1 ions.
extra OH+1 ions.
The effect of pH change on enzyme activity:
RENNIN
RESPIRATORY ENZYME
LIPASE
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Enzymes work: at their best at a specific pH
OPTIMUM pH
called the ____________________
 pH changes in BOTH directions away from the
optimum pH cause the enzyme to become
DENATURE
_______________________ - the
ACTIVE
SITE
_______________________
is damaged and
can no longer fit the substrate, so it cannot
function.

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CO-ENZMYES

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.
B3
Vitamin ______
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.
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The enzyme in a
potato
Catalase enzyme in potato acts on Hydrogen peroxide
H2O2
Catalase enzyme in potato
Hydrogen peroxide
H2
+
O2
Hydrogen gas + Oxygen gas
What’s going on?
1. Catalase decomposes hydrogen peroxide into …
3.1
What is the effect of pepsin on egg-white?
DIGESTS PROTEINS INTO POLYPEPTIDES
3.2
3.3
In which test tube/s will there be a result? TT3
Give a reason for your answer.
(2)
(2)
(3)
HCl (ACID), EGG WHITE (SUBSTRATE) AND PEPSIN (ENZYME)
3.4
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
3.5
What result will be observed?
IN TT 3 – PIECES OF EGG WHITE DISAPPEAR AND A CLOUDY (3)
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SOLUTION RESULTS, AS PROTEIN IS DIGESTED
QUESTIONS
Name the alcohol produced in the making of wine.
ETHANOL
_____________________(1)
In which starchy product is the same alcohol formed,
but lost during the baking process?
_______________________
(1)
BREAD
2 Why is it not possible for natural fermentation to
increase the alcohol content of a fermented product to
20% or more?
(2)
1.
YEAST DIES WHEN IT REACHES 18%
3 Name the enzyme used in making soft-centred
SUCRASE
chocolates. ____________
(1)
4 Name three dairy products made using enzymes.
CHEESE, MILK, YOGHURT ___________
_________________________
(3)
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Why is rennin/rennet used in cheese
It coagulates/clots milk
making?______________________________
(2)
6 Why is it necessary to denature whey proteins when making yoghurt
(1)
IT MAKES THEM CREAMIER
7 Which enzymes are used to give jeans a “stone-washed” look?
(1)
CELLULASE
1.
Why is it better to use enzymes than real stones in the above case?
Give two reasons.
(2)
ECONOMIC: ENZYMES MORE EASILY SOURCED.
FASHION: DOES NOT DAMAGE JEANS
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State one specific use of the enzyme ‘isomerase’.
CHANGES
GLUCOSE INTO FRUCTOSE
_________________________
Why does the use of this enzyme make sense here?
(2)
FRUCTOSE SWEETER, LESS NEEDED, USED IN SLMMNG
FOODS
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
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11.2 Name the enzyme, which was effective in this
experiment.
(2)
AMYLASE

______________________________________________
11.3 What was found to be the most suitable temperature for
the action of this enzyme?
(2)
35OC

_______________________________________________
11.4 What indicator would you have used to show the
presence of starch?
(2)
IODINE
 ___________________________________________________
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)
(2)
48 SECONDS
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11.6 Name the end-product of the digestion of
the cooked starch.
(2)
GLUCOSE
_________________________________________
11.7 Name TWO other factors affecting enzyme
efficiency which could be tested by similar
experiments.
(2)
pH
1. _______________________________________
2. _______________________________________
AMOUNT OF SUBSTRATE or
AMOUNT OF ENZYME
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