Reactions Most reactions take place in a number of steps which need to be carefully controlled if the cell is to function properly Enzymes are the most important controllers of cellular reactions Catalysts ID: 275743
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Slide1
EnzymesSlide2
Reactions
Most reactions take place in a number of steps which need to be carefully controlled if the cell is to function properly
Enzymes are the most important controllers of cellular reactionsSlide3
Catalysts
Catalysts speed up reactions without themselves being involved in the reaction
Enzymes are catalysts made of protein they speed up a reaction without being used up themselves in the reaction
Because enzymes are made in living things they are called biological (or organic catalysts)Slide4
We learned in the chapter on food that proteins are made when amino acids join together
The function of a protein is decided not only by the sequence of amino acids but also by the way the protein folds
Most enzymes are globular proteinsSlide5
Learning Check
What is an Enzyme?
What are catalysts?
To what group of bio-molecules do enzymes belong?Slide6
How enzymes work
Enzymes are not flat they have a 3D structureSlide7
Each enzyme has its own specific shape that will only “fit” the molecule that the enzyme is designed to work on
If the enzyme that breaks starch into glucose meets a fat molecule it will not fit it and will not be able to work on itSlide8
A movie on the action of Enzymes!
http://www.bishopstopford.com/faculties/science/arthur/?sortby=3
http://www.angelo.edu/faculty/nflynn/Biochemistry/
http://www.angelo.edu/faculty/nflynn/Biochemistry/Slide9
Learning Check
Why is the shape of an enzyme important?
Are enzymes flat, 3D or 2D in shape?Slide10
Enzyme Action
The substance that an enzyme acts on is its
substrate
The substance(s) that the enzyme forms is called the product(s)Slide11
A Catabolic enzyme
Amylase converts starch to maltose
Catabolic as it breaks a big molecule into a smaller one
It is produced by saliva glands in mouth and by the pancreasSlide12
An Anabolic Enzyme
DNA Polymerase forms and repairs DNA
Anabolic as it coverts simpler molecules into more complex molecules
Found in almost all living thingsSlide13
Consider This
Amylase is an enzyme found in saliva. It breaks starch molecules into smaller maltose molecules
What is the substrate?
What is the product?
Will amylase break fats into fatty acids + glycerol? Why?
Is this an example of a catabolic or an anabolic reaction? Why?Slide14
And This
DNA Polymerase is an enzyme that builds DNA using tiny molecules in our cells
What is the substrate?
What is the product?
Will amylase build keratin out of peptides? Why?
Is this an example of a catabolic or an anabolic reaction? Why?Slide15
Enzymes work because they have the correct shape to fit the substrate
They have a complex 3 dimensional shape to fit the substrate
When enzymes and their substrates meet and come together they form an Enzyme/Substrate complexSlide16Slide17
Learning Check
What is meant by a substrate?
What is the unit formed when an enzyme combines with its substrate called?
Give an example of an anabolic reactionGive an example of a catabolic reactionSlide18
Reversible
Enzyme Reactions are reversible
Like a key can open or close a lock enzymes can make reactions go in either directionSlide19
Example
In the following example the enzyme can break molecule X into Y+Z but it can also combine Y+Z to form X
X Y
+
ZSlide20
Learning Check
Can enzyme reactions be reversed?Slide21
Naming Enzymes
Enzymes are named by adding the suffix
ase
to the name of their substrateEg. Enzyme that acts on Amylose (starch) is called amylase
Enzymes that act on proteins are called proteasesSlide22
Learning Check
Can you think of a name for enzymes that act on Lipids?
Amazingly enough they are called Lipases!Slide23
Inhibitors
Inhibitors attach to enzymes and destroy their shape
When this happens the enzymes are said to be denaturedSlide24
Nerve Gases
The nerve gases we hear of terrorists using are often inhibitors that attach to enzymes involved in our nerve transmissionsSlide25
Poisoning people the old fashioned way!
Cyanide denatures an enzyme involved in respirationSlide26
Beneficial Inhibitors
Insecticides affect enzymes in insects causing their death
Drugs can affect enzymes involved in pain causing the pain to stop
Antibiotics can affect enzymes in bacteria causing the bacteria to dieSlide27
Learning Check
What is an inhibitor?
How do inhibitors work?
Can you give an example of a harmful inhibitor?Can you give an example of a beneficial inhibitor? Slide28
Enzymes at work!
Enzymes work best in certain conditions
Factors that affect enzymes include
Temperature
pH
Substrate concentration
Enzyme concentration
We will be examining these in experimentsSlide29
Temperature
At very low temperatures ice forms, liquids become solids and enzymes can’t work
As temperature increases molecules start to move and bump into each other causing the rate of reaction to increaseSlide30
Human enzymes work best at body temperature (37
°C)
Plant Enzymes work best at 20-30 °C
Above certain temperatures enzymes start to lose their shape the rate of reaction falls
When the shape is fully lost the enzyme is said to be denatured this is usually a permanent condition
Optimum TemperatureSlide31
pH
pH scale goes from 0 -14
0-7 is acidic
7-14 is basic (or alkaline)Slide32
Optimum pH
Enzymes work over a very narrow pH
Most enzymes work at pH 6-8
Outside this they lose shape and get denatured
The
optimum
or best ph is usually pH 7Slide33
An Exception!
Is our stomach acid or basic?
Do you think there are enzymes in our stomach?
Pepsin is an enzyme in the stomach that works best at pH 2!Slide34
Learning Check
What factors affect enzyme action?
What is the best temperature for (a) human enzymes and (b) plant enzymes
What is meant by pH?Do enzymes work over a narrow or wide pH range?Slide35
Immobilised Enzymes
Bio-processing is the use of enzyme controlled reactions to produce a product
Bio-processing can be used to produce a vast range of products such as cheeses, beer, antibiotics, vaccines, methane gas, food flavours, vitamins and perfumesSlide36
Bioprocessing
Traditionally micro-organisms such as bacteria and yeast were used but since the 1900’s and especially since the 1950’s enzymes are being usedSlide37
Immobilized Enzymes
If enzymes are used freely dissolved in a vessel it can be very wasteful as they are lost at the end of the process
To prevent this problem enzymes are often immobilised or fixed
This means they are attached to each other or an inert substance and can be used repeatedlySlide38
Learning Check
What is bio-processing?
What type of organisms are uasually used in bio-processing?
Why is bio-processing advantageous?Slide39
How to immobilise enzymes
Physical methods
Adsorption
where enzymes are physically attached to inactive supports such as glass beads or ceramics
Enclosed by a membrane
when enzymes are kept within a membrane
Trapped in a gel
, sodium alginate is commonly used this allows substrates in and products outSlide40
Chemical Methods
Bonded to a support
enzymes chemically bonded to a support such as glass beads or ceramics
Bonded to each other
Enzymes are chemically bonded to each otherSlide41
Learning Check
Describe 2 physical methods of immobilising enzymes
Describe 2 chemical methods of immobilising enzymesSlide42
Advantages of Immobilised Enzymes
Efficiency of enzyme is not affected
Immobilised enzymes can be easily recovered from the product so you can get a pure sample of product easily
Immobilised enzymes can be reused this cuts costs
Enzymes frequently become more stable when immobilisedSlide43
Uses of Immobilised Enzymes
Immobilised glucose isomerase converts glucose to fructose which is used to sweeten drinksSlide44
Antibiotics
Penicillin acylase changes the structure of penicillin to make more antibiotics that will fight a wider range of bacteriaSlide45
Lactose
Lactase converts lactose to sweeter sugars glucose and galactose which are then used by food manufacturersSlide46
Learning check
What are the advantages of immobilising enzymes?
Can you name 3 things immobilised enzymes are used for?Slide47
Syllabus Can you.......
Define the term: enzymes
State the nature, folded shape & functions of enzymes.
Explain the role of enzymes in plants and animals including role in metabolismExplain the effects of pH & temperature on enzyme activity.
State the procedure and advantages of Bio-processing.
State the use of Bio-processing.