Post on 09-Mar-2018
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ENZYMEENZYME
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Lesson 1
Learning Objective1.Define enzymes as proteins that function as biological
catalysts.Outline Enzyme Metabolic reaction Enzyme structure Substrate and product
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Enzyme
A protein that can speed up the rate of metabolic reaction without itself being
changed at the end of the reaction.
It is also known as biological catalyst.
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Examples of Enzymes
Carbohydrase
Lipase
Protease
Catalase
Amylase
Starch Phosphorylase
Enzymes are commonly named by “-ase” ending
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Metabolic reaction refers to all the chemical reactions within a living organism
Metabolic Reaction
METABOLISM = ANABOLISM + CATABOLISMMETABOLISM = ANABOLISM + CATABOLISM
'Build up' reaction 'Break down' reaction
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Ana & The Cat
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Ana & The Cat
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Examples of Catabolic Reaction
Proteins Amino acids
Starch Maltose
Fats Fatty acids + Glycerol
Protease
Amylase
Lipase
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Examples of Anabolic Reaction
Glucose Starch
Starch phosphorylase
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Enzyme is Important
Many metabolic reactions are controlled by enzyme. Enzyme is vital in maintaining the normal functioning in
an organism. It is more important than the air you breath, the water
you drink and the food you eat. Without enzyme, reactions would be so slow they
could not occur properly. This may result in death.
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Roles of Enzyme
Enzymes have roles in
Digestion Germination of seeds Photosynthesis Etc.
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Enzyme structure
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Enzyme structure
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Enzyme structureEnzyme is a protein.
It has a very specific shape. It has a 'dent' This 'dent' is called the active site This active site is exactly the right shape and size for
the substrate to fit in.
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Substrate and product
A chemical reaction always involve changing one substance into another.
Substrate is a substance which is present at the start of a reaction
Product is a substance which is present at the end of a reaction
Amylase
Starch Maltose
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Group Discussion:
1.Based on the definition of enzyme, explain why enzymes can be reused over and over again?
2.Digestion and photosynthesis are two of the many reactions that are catalysed by enzymes. Are they catabolic or anabolic reactions? Explain.
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Lesson 2
Learning Objective1.Explain enzyme action in terms of of the 'lock
and key' hypothesis.Outline Active site and substrate Lock and key hypothesis
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Active Site and Substrate
Each enzyme has its own active site which has exactly the right shape and size for the substrate to fit in.
Enzyme is very specific.
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Substrate
Enzyme
ZYX
A CB
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Lock and Key Hypothesis
The reaction between enzyme and substrate is called the lock and key hypothesis.
Substrate Enzyme
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Lock and Key Hypothesis
LEKS
Lock = EnzymeKey = Substrate
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Lock and Key Hypothesis
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Lock and Key Hypothesis
Substrate binds with enzyme at the active site
Stage 1:
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Lock and Key Hypothesis
Enzyme-substrate complex is formed.At this stage, enzyme breaks down the substrate.
Stage 2:
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Lock and Key Hypothesis
Products are formed and they leave the enzyme.Enzyme is ready to bind with another substrate.
Stage 3:
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Lock and Key Hypothesis
Catabolic reaction
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Group Activity
• 1 group – 4 or 5 students• Design a lock and key hypothesis for an
anabolic reaction on a piece of paper.– Label the enzyme, active site, substrate,
enzyme-substrate complex and product.– Write a brief explanation for each stage.
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Anabolic reaction
Lock and Key Hypothesis
Substrates bind with enzyme at the active
site
Enzyme – substrate complex is formed.
At this stage, enzyme combines the
substrates together.
Product is formed andit leaves the enzyme.
Enzyme is ready to bind with another
substrate
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Past Year Question
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Past Year Question
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Past Year QuestionThe figure below shows, in order, four stages in which an enzyme-
controlled chemical reaction may occur.
a) Identify M, N, O and P
b) By referring to the figure, explain why only a small amount of enzyme is needed to catalyse a reaction involving many molecules.
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Lesson 3
Learning Objective1.Investigate and describe the effect of
temperature and of pH on enzyme activity.Outline Characteristics of enzyme
– Enzymes are temperature-sensitive.– Enzymes are pH-sensitive.
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Characteristics of Enzymes
Enzymes are Very specific
Enzymes areproteins
Enzymes are catalysts
Enzymes are affected by..
Enzymeconcentration
SubstrateconcentrationpHTemperature
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Enzyme is temperature-sensitive
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Enzyme is temperature-sensitive• Enzymes have an optimum temperature at which they function
very effectively.
• At low temperatures, enzymes are inactive.
• As the temperature increases, the rate of reaction increases.
– Enzymes gain kinetic energy– They move faster and collide more with substrates, forming
enzyme-substrate complex.• Beyond the optimum temperature, the enzyme activity decreases
as the enzyme is denatured.
– Very high temperature changes the structure of the active site.
– Substrate cannot fit into active site.– No enzyme-substrate complex formed.
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Enzyme is temperature-sensitive
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Enzyme is pH-sensitive
• Enzymes are affected by the acidity or alkalinity of solutions.
• Some work best in acidic environment (eg pepsin)
• Some work best in alkaline environment (intestinal enzymes eg lipase)
• Extreme changes in pH can denature the enzymes.
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Enzyme is pH-sensitive
Enzyme Optimum pH
Amylase 7
Enzyme in stomach, eg. pepsin
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Enzyme in intestine,eg. lipase
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Enzyme is pH-sensitive
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Group Activity
• Find a partner• Draw a graph showing the effect of pH on the
activity of the following enzymes:– Amylase– Pepsin (in stomach)– Lipase (in intestine)
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Past Year Question
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Past Year QuestionThe diagrams represent an enzyme molecule and its substrate. Which
diagram shows these molecules after they are heated to 100ºC?
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Past Year Question
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Lesson 4
Outline Characteristics of enzyme
– Enzymes are affected by • substrate concentration• enzyme concentration.
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Substrate Concentration
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Substrate Concentration
• As the substrate concentration increases, the speed of enzyme reaction also increases.
• But, there comes a time when any more increase in the substrate concentration does not increase the speed of enzyme reaction.
Why?
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Substrate Concentration
• At low substrate concentrations, collisions between enzymes and substrates are infrequent and reaction proceeds slowly.
substrate enzymes
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Substrate Concentration
• As the substrate concentration increases, the rate of reaction initially increases because collisions between enzymes and substrates become more frequent.
substrate enzymes
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Substrate Concentration
• What do you think happen if there is a further increase in substrate concentration?
substrate enzymes
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Group ActivityDraw a graph showing the effect of enzyme
concentration on enzyme activity.
Think of how many enzyme-substrate complex formed when there is less/more enzyme
molecules present.
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Substrate Concentration
• What do you think happen if there is a further increase in substrate concentration?
substrate enzymes
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Lesson 4
Outline Enzymes in germinating seed
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Enzymes in Germinating Seed
Germination is the growing of young plant.
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Enzymes in Germinating Seed
• Germination begins with water absorption.• Water activates the enzymes in the seed.• Enzymes digest the food stored in the seed into
smaller soluble substances.Complex food Enzyme Digested food
Starch Carbohydrase Simple sugars
Proteins Protease Amino acids
Oils Lipase Fatty acids and glycerol
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Past Year Question