Enzymes

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  • Created by: helizm69
  • Created on: 06-04-18 11:33
what are enzymes?
They are biological catalysts which allow reactions to occur at the same rate as they would outside the human body. without enzymes reactions would occur too slowly to maintain human life. They are globular proteins and have a 3D shape.
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Activation Energy/Ea?
Ea is the amount of energy neccessary for a chemical reaction to occur. enzymes lower this energy barrier and allow reactions to take place at a level which is able to sustain life. The activation energy can be lowered by heating-damage body cells.
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How enzymes work?
the enzyme and substrate come together to form an enzyme-substrate complex once the substrate has attached at the active site. they then form an enzyme-product complex before the products are released from the enzyme.
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What is the enzyme like at the end of the reaction?
The enzyme is unchanged at the end of the reaction and is generally larger than the substrate. The majority of amino acids in the enzyme function to maintain 3D shape
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What types of reactions are there?
Anabolic reactions produce products that are built up whilst catabolic reactions breakdown molecules.
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Lock and key hypothesis?
enzyme is a complementary shape and the substrate fits in exactly.
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Induced fit hypothesis?
The substrate and the enzymes active site are not quite complimentary. the active site changes shape in the binding and moulds to the substrate. the enzyme distorts the substrate and puts strains on the bonds & speeds up reaction.Strain lowers Ea.
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Active site?
3-12 amino acids present at the active site. This is the place where the substrate binds to the enzyme. at the active site opposite charges attract(+/-).
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Are enzymes specific?
yes, one type of enzyme only fits one type of substrate.
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Cofactors
this is a group made up of helpers including coenzymes and prosthetic groups which make it easier for the substrate to bind bu influencing the shape of the enzyme. They are obtained from the diet & are nonprotein subs. including metal ions,eg.iron
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Coenzymes
These are organic molecules(contain carbon) and are not permanently attached. e.g. NAD,FAD,Q10. without these enzymes will not function properly.
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Prosthetic Groups
eg.haem in haemoglobin. these work to help shape the enzyme to the optimum for substrate attachment.
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What affects reactions?
Enzyme molecules need to collide with substrate molecules in order to produce products. therefore, factors affecting the chance of collision influence rate of reaction. enzymes are globular/3D so factors affecting shape influence rate of reaction.
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Affect of LOW temperature on rate of reaction?
increases in temperature cause an exponential increase in enzyme activity. increased kinetic energy for collisions means the rate of enzyme substrate complex developments increase.
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Affect of OPTIMUM temperature on rate of reaction?
This is the maximum rate of enzyme activity.
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Affect of HIGH temperature on rate of reaction?
(above 40'C usually) Further increase in temperature and KE gives sharp decline as bonds holding tertiary structure of molecules are broken and active site loses complementary shape-enzyme denatured. Rate is not always zero degrees at zero.
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Affect of LOW pH on rate of reaction?
changes in pH disrupt ionic bonds in tertiary structure causing a change in shape. High concentration of H+ causes negatively charged R groups to lose their charge which prevents substrate from binding to active site.
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Affect of OPTIMUM pH on rate of reaction?
At optimum pH the charges on enzyme and substrate best suit each other and ES complex formed.
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Affect of HIGH pH on rate of reaction?
low concentration of H+ causes positively charged R groups to lose their charge which stops substrate attachment. Extreme changes in pH mean they will be irreversibly damaged.
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Affect of enzyme concentration on rate of reaction?
more enzymes molecules present means more active sites and more successful collisions. Enzymes tend to be limiter in most reactions but if there is insufficent substrate then activity will level off.
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LOW enzyme concentration?
The more enzymes the greater chance of collisions and the more ES complexs are made.
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HIGH enzyme concentration?
substrate concentration is the limiting factor as there is not enough substrate to fill the active sites.
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Affect of LOW substrate concentration on rate of reaction?
increase in concentration means more enzyme activity and greater cocnentration of substrate means more collosions and more ES complexes formed.
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Affect of HIGH substrate concentration on rate of reaction?
increases in concentration do not cause further activity as enzymes are fully employed and all active sites are occupied.
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Card 2

Front

Activation Energy/Ea?

Back

Ea is the amount of energy neccessary for a chemical reaction to occur. enzymes lower this energy barrier and allow reactions to take place at a level which is able to sustain life. The activation energy can be lowered by heating-damage body cells.

Card 3

Front

How enzymes work?

Back

Preview of the front of card 3

Card 4

Front

What is the enzyme like at the end of the reaction?

Back

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Card 5

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What types of reactions are there?

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