BIOLOGY F4 C4 4.2 Enzyme

8/7/2019 BIOLOGY F4 C4 4.2 Enzyme

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Scientists aregreat people straightens

the ? to become !-- Anonymous


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4.5 Enzymes

Lesson Review


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Role of Enzyme in Organisms

Enzymes are biological catalysts that regulate

almost all the cellular reaction they speed

up biochemical reactions in the cells


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General Characteristics of Enzymes

Enzymes are proteins synthesised by living

organisms

In enzymatic reactions, enzymes bind to theirsubstrates and convert them to product


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enzyme

Substrate products


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Enzymes speed up the rates of chemical

reactions, but remain unchanged at the end

of the reactions.

They are not destroyed by the reactions they

catalyse.


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Enzymes have

specific sites called

active sites tobind to specificsubstrates thats

why enzymes are

highly specific


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Each enzyme can

only catalyse one

kind of substrate Amylase starch

molecule can fit in

Sucrase starchmolecule cannot fit

in


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Enzymes are needed in small quantities

Reason: they are not used up but released at

the end of reaction


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Most enzyme-catalysed reactions are reversible

or


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Naming of Enzymes

Most enzymes have a name derived by adding

the suffix ase at the end of the name of their

substrates

Eg: Enzyme for hydrolisis of lactose is lactase

Eg: Sucrose: sucrase

Eg: Lipid: lipase


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Naming of Enzymes

Then pepsin? Trypsin? Rennin?

They were named before this systematic way

naming enzymes was formed


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Naming of Enzymes

Then pepsin? Trypsin? Rennin?

They were named before this systematic way

naming enzymes was formed


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Sites of Enzyme Synthesis

Enzymes are proteins

So RIBOSOMES are

also the sites ofenzyme synthesis


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2Types of Enzyme

INTRACELLULARENZYMES Enzymes synthesised and

retained in the cell for the

use of the cell itself

They are found in: Cytoplasm

Nuclues

Mitochondria

Chloroplast

EXTRACELLULARENZYMES Enzymes synthesised in the

cell, but secreted from the

cell to work externally

Example: Digestive enzymes produced

by the pancreas, transported

to duodenum


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Production of Extracellular Enzyme

Protein produced in ribosomes

Spaces between Endoplasmic Reticulum(ER)

Wrapped in vesicles. Bud off

Fuse withG

olgi apparatus.

Maybemodified here. Bud off

Fuse with plasma membrane, releasingout as Enzymes


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The Mechanism of Enzyme Action: TheThe Mechanism of Enzyme Action: The

LOCK AND KEY HypothesisLOCK AND KEY Hypothesis

Enzyme + Substrate Enzyme-substrate

Complex

Enzyme + Product

ACTIVESITEACTIVESITE


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The Mechanism of Enzyme Action: TheThe Mechanism of Enzyme Action: The

LOCK AND KEY HypothesisLOCK AND KEY Hypothesis

Enzyme + Substrate

Substrate: KEY

Enzyme: LOCK


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Review

Enzymes have

specific sites called

active sites tobind to specificsubstrates thats

why enzymes are

highly specific


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CAN WESTOP ENZYMES???

Question:


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YES!

Answer:

Thats why we have activators &

inhibitors. Factors taking place also

includes:(i) Temperature

(ii) pH

(iii) Substrate concentration(iv) Enzyme concentration


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CONT

ROLLING

ENZ

YMES

Yes!! We can do it~


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Faster!! Faster!!!

Helper molecules

called COFACTORS

Inorganic, eg:

Ferum

Copper

Organic cofactor, eg:

B vitamins


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Slowing it down.../STOP!!

INHIBITORS

They often bondto the protein,changing the

overall shape ofthe enzyme

Remember, whenthe shapechanges, the

enzyme will notwork the sameway


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Slowing it down./STOP!!

INHIBITORS

Example: heavy metals such as lead (Pb) and

mercury (Hg)


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TEMPERATURE

Factor 1


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Factor 1: Temperature

Low Temperature

Enzyme-catalysed reaction takes place slowly


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As the temperature increases

The movement of substrate molecules increases

The rapid movements of the substrate molecules

increase their chance of colliding with one

another and with the active sites of the enzyme

molecule


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This is only true up to OPTIMUM TEMPERATURE

O.T.: Temperature at which an enzyme catalyses a

reaction at the maximum rate

Most human enzyme ~37oC, plant ~ 25oC


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High temperature

No increase in rate of reaction

Reason: Bonds that hold enzyme molecules

together begin to break at high T, changing the 3D

shape of enzyme, eventually destroying their

active sites.


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High temperature

The enzyme lose their activities and are said to be

DENATURED!!

Denaturation is IRREVERSIBLE!


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Optimal functioning of enzyme: 37oC

Most organisms cannot survive at

temperature above40o

C


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Graph: The effects of temperature on theGraph: The effects of temperature on the

rate of an enzymerate of an enzyme--catalysedcatalysed reactionreaction


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pH

Factor 2


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Factor 2: pH

Enzymes are sensitive to thechanges of pH in theirsurroundings.

A change in pH can alter thecharges on the active sites ofthe E and the S surfaces

This can reduce the ability ofboth molecules to bind each

other.


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Graph: The Optimum pH of Some EnzymesGraph: The Optimum pH of Some Enzymes

Pepsin stomach (acidic condition, pH2)

Trypsin duodenum (alkaline condition, pH8.5)


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Factor: pH

Effects of pH on enzymes

are normally reversible

pH in environment back

to optimum level, ionic

charges on the active

sites are restored


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Factor 3: Substrate Concentration

[substrate] , the more substrate molecules

are available to bind the active sites of the

enzymes => more products will be produced


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Reason: More chances of collisions between

substrate molecules and the enzyme molecules

for a catalytic reaction to take place.


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Limiting factor: [ENZYME].

Must have enough enzyme molecules to

catalyse the additional substrate molecules


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Thus, the rate of

reaction is directly

proportional to the

[substrate] until thereaction reaches the

maximum rate


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After maximum rate: all active sites of theenzymes molecules are filled and engaged incatalysis.The enzyme is said to be satured.

So what to do? [enzyme]


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ENZYMECONCENTRATION

Factor 4


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Factor 4: Enzyme Concentration

[Enzyme] , more enzyme molecules available.

So, more active sites are made available for

the catalytic reaction.


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Factor 4: Enzyme Concentration

Limiting factor: [substrate molecule]


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Graph: The Relationship between theGraph: The Relationship between the

rate of reaction and enzyme concentrationrate of reaction and enzyme concentration

Reaction rateReaction rate direct proportionaldirect proportional to [enzyme],to [enzyme],

until a maximum rate is achieveduntil a maximum rate is achieved


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Homework

Worksheet. Draw out all 4 graphs for Factors

Effecting Enzyme Activity


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Next class

Quiz

The uses of enzyme very important!!


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Science-Technology-Society

Raw fruits with enzymes

http://www.healingdaily.com/detoxification-

diet/enzymes.htm

Garbage enzymes

Making your own enzyme juice? Eg:

dragonfruit enzyme, papaya enzyme?

Enzyme found in your washing powder


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References

http://www.chem4kids.com/files/bio_enzyme

s.html

BIOLOGY F4 C4 4.2 Enzyme

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