C4 Enzymes Flashcards
What are the different stages of the process of Enzyme action
Enzyme substrate bind together at the active site
An enzyme substrate complex is formed
The substrate is broken down to produce products
Enzymes, lock and key model
Active site has a specific shape
Substrate also has a specific shape
Thee 2 are therefore complementary
Enzymes examples
Catalyse (intercellular) Protease- pepsin, trypsin Carbohydrase - amalyse, maltase Lipase (Last three are all extracellular)
What are enzymes made out off?
Globular portions
Highly specific (R groups) 3D shape
Specialised region with a highly specialised specific active site
Generally soluble (hydrophilic r groups on the outside, with hydrophobic generally on inside).
Introduced fit model (Confirmational change)
Puts the bonds in the substrate under strain
This can weaken a particular bond(s) in the substrate and therefore lower the activation energy required
What is meant by biological catalysts
Speeds up metabolic reactions
Anabolic (building up)
Catabolic (breaking down)
Enzymes lower activation energy
Q10 Temperature coefficient
It is a measure of temperature consistency of an enzyme reaction. It indicates how much the rate of reaction increases with a change of 10°C.
What’s optimum temperature
Temperature at which enzyme has highest rate of activity
How does temperature affect enzyme activity
As temperature increases kinetic energy of the particles increase, therefore they move faster and collide more frequently. There is an increase in frequent successful collisions between substrate and enzyme.Therefore the rate of reaction increases.
How can temperature cause enzymes to denature
An increase in temperature increases the vibrations in the bonds holding the particles together, until bonds strain, then break, resulting in a change in the precise tertiary structure. As a result the active site changes shape.
How does pH affect enzyme activity
(Potential hydrogen)
The active site can only be in the right shape at a certain hydrogen concentration (optimum pH). The more hydrogen ions present the less the R groups are able to interact with each other. The hydrogen ions bind to the O2- atoms. The reverse is true when fewer hydrogen ions are present (enzymes can only function at narrow pH range).
What’s renaturation
If the pH returns back to normal/ optimum then the protein will resume its normal shape and catalyse the reaction again
What is V max
The rate of reaction increases until its maximum (Vmax) where the substrate or enzyme no longer becomes a limiting factor (can’t increase the rate).
How does substrate and enzyme concentration affect enzyme activity
As they increase the concentration and increase the number of substrate molecules atoms or ions in a particular area this results in a higher collision rate with the active site of enzymes as a result this increases the rate and amount of formation of enzyme substrate complexes and therefore increases the rate.
Increasing the number of enzymes will increase the number of available active sites and therefore result with a faster rate of binding.
What’s a cofactors, and how do they function?
A helper molecule. A non protein ‘helper’ component that is essential for some enzymes to carry out their function as biological catalysts
They may transfer atoms or groups from one reaction to another in a multi-step pathway or actual form part of the active site of the enzyme.
If a cofactor is an organic molecule what is it called
Coenzyme
Where are inorganic cofactors obtained from?
Give an example
Via the diet as minerals including iron, calcium, chloride and zinc ions.
E.g the enzyme amylase contains a chloride ion that is necessary for the formation of the correctly shaped active site.
What are coenzymes derived from?
E.g
From vitamins (a class of organic molecules found in the diet).
E.g Vitamin B3 is used to synthesis NAD (nicotinamide adenine dinucleotide), a coenzyme responsible for the transfer of hydrogen atoms between molecules involved in respiration.
Vitamin B5 is another example
Cofactors: prosthetic group, function
E.g
They are required by certain enzymes to carry out their catalytic function . While some cofactors are loosely or temporarily bound the to the enzyme protein (to activate them), prosthetic groups form a permanent feature of the protein.
E.g zinc ions form an important part of the structure of carbonic anhydrase (an enzyme necessary for the metabolism of CO2).
What is meant by competitive inhibition?
A molecule or part of a molecule that has a similar shape to one substrate of an enzyme can fit into an active site of the enzyme, blocking substrate answering active site and therefore preventing enzyme from catalysing reaction. The enzyme cannot carry out its function, set to be inhibited.
What do competitive inhibitors and substrates compete for?
And how does this effect the rate of reaction
They both compete to bind to the active site of enzyme catalysing one reaction.
This will reduce one number of substrate molecules attaching in a given time, and hence reduce the rate of reaction.
How does competitive inhibitors effect the rate of reaction?
Reduces one rate of reaction for a given conc of substrate, but doesn’t change the Vmax of the enzyme it inhibits. If the substrate conc increases enough there will be more substrate than inhibitors that the original Vmax cab still be reached.
Competitive inhibitors examples:
Statins, competitive inhibitors of enzyme used in the synthesis of cholesterol (used to reduced high blood cholesterol conc).
Aspirin irreversibly inhibits one active site of cox enzymes, preventing the synthesis of prostogladins and thrombaxane (chemicals responsible for producing pain and fever).
Non-Competitive Inhibition (3):
The inhibitor binds to the enzyme at an allosteric site.
Binding causes tertiary structure enzyme to change, causing active site to change shape too.
Results active site no longer having complementary shape to substrate, unable to bind (enzyme can’t carry out function, ‘inhibited’).
Non- competitive inhibitors effect on rates of reaction
Increase in concentration of enzyme or substrate will not overcome affect of a non-competitive inhibitor. Increasing concentration of inhibitor however would decrease the rate of reaction further as more active sites become unavailable.
Non-competitive inhibitor examples
The binding of an inhibitor may be reversible or non-reversible.
Proton pump inhibitors (PPI’s) are used to treat long term indigestion. They irreversibly block an enzyme system responsible for secreting Hydrogen ions into the stomach.They are effective in reducing one’s production of excess acid, which if left untreated can lead to formation of stomach ulcers.
What is end-product inhibition and example of?
Non-competitive reversible inhibition
End-product inhibition
Term used for enzyme inhibition occurs when the product of the reaction act as an inhibitor to the enzyme that produces it (serves as a negative feedback control mechanism for the reaction). Excess products are not made and resources are not wasted.
End-product inhibition examples
Respiration is the metabolic pathway resulting in production of ATP. Glucose is broken down in a number of steps. First involves one addition of two phosphate groups, glucose molecules, which results in one initiate breakdown of one glucose molecule, is catalysed by the enzyme phosphorustotindce (PIK).This enzyme is competitively inhibited by ATP. ATP therefore regulators own production. When the levels of ATO are high more ATP binds to allosteric site of PIK, preventing the addiction of the second phosphate group to glucose. Glucose is not broken down and ATP is not produced at one same rate.. As ATP is used up, less bind to PIK and the enzyme is able to catalyse the addition of the second phosphate group to glucose. respiration resumes, leading to one production of more ATP.
