lesson 13. state that enzymes are globular proteins with a specific tertiary structure state that...
TRANSCRIPT
Lesson 13
State that enzymes are globular proteins with a specific tertiary structure
State that enzymes catalyse metabolic reactions
State that enzyme action may be extracellular or intracellular
State that enzymes catalyse metabolic reactions
Describe the mechanism of enzyme action Explain what is meant by enzyme-substrate
complex and enzyme-product complex Describe how enzymes lower activation energy Explain the importance of coenzymes and
cofactors in enzyme controlled reactions
Look at the two jellies, what has happened and why?
Think, pair, share
Enzymes are globular proteins with a specific tertiary structure
Enzyme action may be intracellular or extracellular
Enzymes are biological catalystsEnzymes catalyse metabolic reactionsEnzymes lower activation energy because
of the way the active site is shaped to fit the substrate
Use the plasticene to model the lock and key model of enzyme action
They are proteins of high molecular weight
They are biological catalysts
They are sensitive to temperature changes being denatured at high temperatures
They are sensitive to pH
They are generally specific in the reactions they catalyse
Enzymes possess an active site within which chemical reactions take place
Substratemolecule inthe ACTIVESITE
Enzyme molecule
The Active Site
Substratemolecules(complementaryshape to activesite)
Enzymemolecule
Productmoleculesdiffuse awayfrom theactive site
Substrate molecules bind with enzyme molecules at the activesite as a consequence of their complementary shapes. This is the basis of the LOCK AND KEY MODEL of enzyme activity
Enzyme substrate complexes form
Activesite
Reactionoccurs
Read page 127 in the text book Create a comparison table for lock and
key and induced fit hypothesis
Lock and Key Model Induced Fit Hypothesis
The Lock And Key Model
In an enzyme - catalysed reaction, the enzyme bindsto the substrate to form a complex
An enzyme - substrate complexforms
A reactionoccursforming anenzyme - productcomplex
Products diffuseaway from theactive site
Enzymemolecule
The lock & key modelproposes that the substratebinds to the active sitewhich it fits exactly, like akey in a lock
S
The Induced Fit Model
This model takes into account the fact that proteins (enzymes) have some three-dimensional flexibility
SUBSTRATE
Substrate binds to the enzymeat the active site
Binding of the substrateinduces the enzyme to changeshape such that there is anexact fit once the substratehas bound
Enzyme Molecule According to this model, reactions canonly take place AFTER induced fit has occurred
Specificity, The active site of an enzyme is a specific shape,
depending on the reaction that it catalyses, meaning that other molecules won’t fit into the active site
Active site, The area on an enzyme to which the substrate
binds Lock and key hypothesis,
The theory of enzyme action in which the enzyme active site is complementary to the substrate molecule, like a lock and key
Induced-fit hypothesis, The theory of enzyme action in which the
enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it
Enzyme-substrate complex, The intermediary formed when a substrate
molecule binds to an enzyme molecule Enzyme-product complex
The intermediate structure in which product molecules are bound to an enzyme molecule lowering of activation energy
Answer the following questionDescribe the mechanism of enzyme action
Use as many key terms as possible Person with the most key terms used
correctly wins a prize
Swap answers Highlight all the key terms in their response
Enzyme Substrate Enzyme substrate complex Enzyme product complex Product Collision Active site Lock and key Induced fit
Maximum mark of 9, lose a mark for every incorrectly used term or missed term
Cofactor: substance that must be present for enzyme controlled reactions to take place at the appropriate rateProsthetic group: inorganic ion that is a
permanent part of the enzyme contributing to its 3D shape
Coenzyme: organic molecule that binds either just before or at the same time as the substrate (help reactions take place in sequence)
Inorganic ions: either bind to enzyme or substrate to help form the enzyme substrate complex
Role play, model or draw the effect of coenzymes and cofactors in enzyme controlled reactions
State that enzymes are globular proteins with a specific tertiary structure
State that enzymes catalyse metabolic reactions
State that enzyme action may be extracellular or intracellular
State that enzymes catalyse metabolic reactions
Describe the mechanism of enzyme action Explain what is meant by enzyme-substrate
complex and enzyme-product complex Describe how enzymes lower activation energy Explain the importance of coenzymes and
cofactors in enzyme controlled reactions
One form of COPD develops because enzymes are released by phagocytes entering the alveoli. This enzyme action can break down elastin in the lining of the bronchioles and alveoli. Use the example of elastin breakdown to explain the induced-fit hypothesis of enzyme action [5]
elastin is substrate (elastin / substrate) binds to / fits into , active site ; active site / enzyme / elastase / substrate / elastin,
shape changes idea of closer fit (between active site and
substrate) more bonds form (between substrate and active
site) forms enzyme-substrate-complex / ESC idea that (change in shape of active site)
destabilises / weakens , bonds (in substrate) / substrate
activation energy reduced idea of further shape change of, active site /
enzyme, after products form
Make a glossary of key enzyme terms