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What are enzymes? enzymes are proteins
that function as biological catalysts
a catalysts is a substance that usually speeds up the rate of a chemical reaction and is not changed by the reaction
thus enzymes speed up the rate of metabolic reactions in the cells
Enzymes work enzymes lower the minimum
amount of energy required for chemical reaction to occur (activation energy)
this allows biochemical reactions to take place at a faster rate in the cells of living organisms at body temperature which is usually low
enzymes catalyse metabolic reactions (i.e. chemical reactions that sustain life) in a cells
metabolic reactions are either breakdown reactions -catabolism or build up reactions - anabolism
Naming of Enzymes enzyme are named
according to the reaction they catalyse
a suffix – ase is usually added to the name of the substrate of the reaction catalysed by the enzyme
sometimes they are given special names such as catalase & amylase
catalase is the fastest acting enzyme
How Enzymes Work
“Lock and Key” Model each enzyme has a shape that allows it to
catalyse one reaction
reactant(s) in an enzyme – catalysed reaction is/are called substrate(s)
enzyme’s molecule has a specific shape which is complementary to that of a substrate –this is called active site
the substrate fits into the active site of the enzyme the same way a ‘key fits into a lock’ -this is called “ lock and key” model
the substrate (the ‘key’) fits exactly into the active site (the ‘key hole’) of the enzyme (the ‘lock’)
an enzyme-substrate complex is formed
the substrate undergoes a chemical change –a new substance, the product, is formed
the product is released from the active site
the free unaltered active site is ready to receive fresh substrate
General Properties of Enzymes enzymes are all Proteins enzymes are specific in
reaction they catalyse enzymes are not changed by
the reaction they catalyse i.e. they can be used again and again
enzymes are influenced by change in temperature
enzymes are influenced by change in pH
enzymes work best at particular temperature (37 oC in humans)and pH (pH 2 for pepsin & pH 7 for most enzymes)
Factors Affecting Enzyme Activity enzyme activity is
determined by measuring the rate of reaction that the enzyme catalyses
this is usually measured by measuring the products formed per unit time
enzyme activity is affected by; temperature, pH & substrate concentration
Effect of Temperature on Enzymes at low temperature (e.g. 0°C) enzyme activity is
low because the movement of molecules is slow due to low kinetic energy
the collision frequency between enzyme and substrate is therefore low
increasing the temperature, increases kinetic energy of molecules thus speeding up their movement, collision frequency between the substrates and the enzymes increases therefore enzyme activity increases
maximum enzyme activity is at 40°C – due to maximum collision frequency between enzymes and substrates molecules – this is called optimum temperature (i.e. the temperature at which the enzyme works fastest)
enzyme action decreases above 40°C because the enzymes are denatured by excess temperature (i.e. the shape of active site is altered & substrates molecules can no longer fit into it)
when all the enzymes are denatured, at 60°C, enzyme activity stops
Effect of pH on Enzymes enzyme activity is greatest within a
narrow range of pH, since all the enzymes are functioning normally because their active sites have the correct shape
this is called the optimum pH
change in pH from the optimum, alters the shape of active site thus affecting the ability of the substrates to bind to the active site & so enzyme activity decreases
a major change in pH from the optimum denatures the enzymes so enzyme action stops
from the graph, what is the optimum pH for;
enzyme X?
enzyme Y?
Investigation plan and carry out an
experiment to investigate the effect of changes in either temperature or pH on enzyme activity
systematically analyse the problem above and produce a logical plan for your investigation
identify the key variables and attempt to control them in your procedure
Observation
Hypothesis & Identification of
variables
Experiment
Raw data collection &
recording
Raw data processing &
presentation
Analysis of presented data
Conclusion
Evaluation
Research Question
Use of enzymes in: germination of seeds, biological washing products & food industry
enzymes are widely used in industry because; they work at lower temperature
than other catalysts thus reducing cost of fuel
they are not destroyed by the reaction they catalyse, thus they can be used over and over again
applications of enzymes in day –to – day life include; hydrolysis of stored food during
seed germinations use of enzymes in food industry
such as juice extraction, brewing industry to make beer
making of biological washing powders
producing antibiotic penicillin
Use of enzymes in: germination of seeds
enzymes in seeds breakdown stored food substance into soluble end products which can be translocated to growing regions
starch is broken down to maltose by the enzyme amylase
fats/oils are broken down by lipase to fatty acids and glycerol
maltose & fatty acids are respired to provide energy for germination
Production of apple juice
enzyme pectinase is added to crushed apple fruit pulp
the enzyme breaks down pectin in plant cell walls releasing more juice from the crushed apples
Use of enzymes in biological washing powders
presence of enzymes in biological washing powders increase the efficiency of the washing powder in removing stains from clothes because: stains may be protein or fat
which are not removable with detergent only
presence of lipase breaks down fat stain into fatty acids & glycerol
presence of protease breaks down protein stain into amino acids
fatty acids, glycerol & amino acids are soluble in water thus easily washed away
Controlling the temperature of the wash
temperature of the wash needs to be carefully controlled because:
high temperature denatures enzymes , so enzymes will not work
at low temperature, enzymes are inactive thus they work slowly
constant optimum temperature such as 37 oCmaintains optimum conditions for enzyme activity
Use of microorganisms & industrial fermenters to manufacture the antibiotic
industrial fermenters are large metal tanks that uses microorganisms to produce useful products such as antibiotics such as penicillin
the organism involved, fungus Penicillium is added to the tank together with nutrients such as sugar & ammonium salts (or amino acids)
penicillium produce enzymes which converts the substrate into penicillin, antibiotic used to cure bacterial infections
sugar provide energy for respiration while ammonium salt is used to produce proteins & nucleic acids
Maintaining suitable conditions in the industrial fermenters
suitable conditions such as optimum pH, optimum temperature and supply of oxygen & nutrients are required
air is bubbled through to provide oxygen for respiration
stirring using paddles keeps microorganism suspended so they always have access to nutrients & O2 and rolls the fungus into little pellets making it easy to separate liquid from the culture
water -cooled jacket maintains a constant temperature of 24 0C
probes monitor the temperature & pH in the tank - pH is maintained at 6.5 by adding alkalis where necessary
after 6 days, fermentation is complete & the mixture is drained & filtered
penicillin is then extracted
Role of the fungus Penicillium in the production of antibiotic penicillin
nutrient medium (sugars and, ammonium salts & ammonia)is placed in a bioreactor
air, to provide oxygen, is bubbled through the medium
fungus penicillium is added to the medium
paddles mix the fungus with the medium
temperature kept at 24 oC & pH kept at 6.5
fungus penicillium produces enzymes that converts the substrate into penicillin
penicillin is the antibiotic used to cure bacterial infections
Revision activity
after reading pages 39 -48 of your biology textbook and your lesson notes, attempt Revision Questions 1 - 4 on page 48.
Summary Questions:
Define the terms catalyst & enzymes
Describe an experiment you would carry out to investigate the effect of changes in temperature on enzyme activity
Describe an experiment you would carry out to investigate the effect of changes in pH on enzyme activity
Explain enzyme action in terms of the ‘lock & key’ model
Explain the effect of changes in temperature and pH on enzyme activity
Describe the role of enzymes in the germination of seeds, and their uses in biological washing products & in fruit juice production
Outline the use of microorganisms and fermenters to manufacture the antibiotic penicillin and enzymes for use in biological washing powders
Describe the role of the fungus Penicillium in the production of antibiotic penicillin