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Chemical
compositionof cell
(enzyme)Biology chapter 3
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ENZYMES
Catabolism
-breaking downsubstance to produceenergy for work
Anabolism
-synthesis of newsubstances
Protein molecules madeby living cells, acting
catalysts that speed uprate of metabolic reaction
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Enzyme
Intracellular
Catalysesreaction within
cell
Extracellular
Leave cell andcatalysesreactionoutside
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Intracellular EnzymeName of
intracellular
enzyme
Type of reaction Location
DNA polymerase DNA synthesis Nucleus
Thiokinase Fatty acidscatabolism
Outside ER
Pyruvatecarboxylase
Cellular respiration Mitochondria
Oxydoreductase Cellular respiration Mitochondria
ATP synthetase ATP synthesis Mitochondria
ATPase Catabolic releaseof energy
Mitochondria
Carbonicanhydrase
CO2 + H2O
H2CO3Red blood cell
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Extracellular EnzymeName of
intracellular
enzyme
Where it
comes from
Where it
works
Food acted
on
Substance
produce
Amylase Salivaryglands
Mouthcavity
Starch Maltose
Pepsin Stomach wall Stomach Protein Peptides
Trypsin Pancreas Smallintestine
Starch Maltose
Lipase Pancreas Smallintestine
Fat Fatty acid
Maltose Wall of smallintestine
Smallintestine
Maltose Glucose
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Generalcharacteristics
of Enzyme
Speed uprates of
biochemicalreactions in
cell only smallamount of
enzyme neededto catalyse a lot
of substrate
Very specific-each class ofenzyme will
catalyse only
one particularreaction
Not used up/ destroyedin reaction,but can be
reuse
Enzymecatalysereversiblereactions
Only able towork with thepresence ofcoenzyme
Affected bychanges oftemperature
& pH
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SITES OF ENZYME SYNTESIS
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The secretory vesicle transport enzyme to plasma membrane & fuses withplasma membrane. Then, enzyme release outside the cell
In Golgi Apparatus, enzyme further modified then packed in a secretory vesicle
Transport vesicle then fuse with Golgi Apparatus & release enzyme into Golgiapparatus
When enzyme synthesis has completed, it is extruded into the interior of ER. Itis then encapsulated in transport vesicle
Amino acid will form enzyme molecules according to the information broughtby RNA
RNA the leaves the nucleus through nuclear pore & attaches itself to ribosomelocated on the ER
Instruction for making the extracelullar enzyme is transcribed from DNA toRNA in nucleus
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MECHANISM OF ENZYME ACTION
(Lock & Key Model)
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FACTORS
AFFECTINGENZYME
ACTIVITY
pH
-each enzyme has an optimal pH -help it to maintain its 3D-shape
-optimal pH value are different for each enzyme
-pepsin= 2, salivary amylase= 7 ,Trypsin = 8-9
Temperature
-generally, the rate of reaction doubles for every 10Crise in temperature, & peaks at about 37C to 40C
-higher temperature can cause denatured
-denatured enzyme has a permanent change in its
molecular structure that cannot be reversed by cooling
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FACTORSAFFECTING
ENZYMEACTIVITY
Substrate Concentration
-increasing the substrate concentration will increase the rate of reaction
-increasing substrate concentration after the maximum point does not further affect the rateof reaction
-little substrate but many enzymes-rate of reaction is low
-more substrate but still many unused enzyme- increase the reaction a little bit
-equal amount of substrate & enzyme- highest possible reaction rate
-more substrate than enzyme-reaction still the same
Enzyme Concentration
-in an enzyme-catalysed reaction, rate of reaction is directlyproportional to the concentration of enzyme used.
-more enzymes can provide more active sites for substrate-enzyme
complex formation
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FINISH!!