Chemical Composition of Cell (Enzyme)

7/30/2019 Chemical Composition of Cell (Enzyme)

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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!!

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Chemical Composition of Cell (Enzyme)