Enzymes Flashcards
(37 cards)
What are enzymes?
Enzymes are biological enzymes which catalyse specific chemical reactions.
What are the different functions of the enzyme?
- Digestion of carbohydrates,fats and proteins
- Blood Clotting
- Defense i.e. the immune system
- Movement
- Nerve Conduction
What two types of enzymes are there?
Extracellular or Intracellular
What are the names of the specifc types of enzymes that catalyse specific reactions?
- nucleases
- proteases
- polymerases
- kinases
What is an issue of an enzyme having a defect?
They can cause disease such as phenylketonuria (a disease where-by the Phe cannot be turned inro Tyr
Antibiotics, anti-inflammatory and anticancer drugs are all use enzymes as…?
A drug target. For example, antibiotics such as penicillin can inhibit cell wall synthesis, anti-inflammatory agents such as asprin blocks prostaglandins and anticancer drugs such as methotrexate, a folate analouge that interferes with the synthesis with DNA precusors.
What are the key properties for enzymes?
- increase the rate of reaction up to 10 billion fold
- are specific
- remain unchanged at the end of a reaction and do not alter the equlibrium position
- facilitate the reaction by decreasing the amount of free energy is needed by the reaction
How does the enzyme bind to the substrate?
The enzyme has a 3D cleft, also known as the active site, which binds to the substrate using electrostatic, hydrophobic, hydrongen bonding and van der Waals interactions creating binding energy which helps reduce the amound of free energy needed.
How can you prove the existence of active sites?
From x-ray crytallography and kinetic studies of enzyme acitivty.
What is the lock and key model?
The lock-and-key model states that the substrate acts as a ‘key’ to the ‘lock’ of the active site. The active site and substrate are exact matches for each other, similar to puzzle pieces fitting together. In this model, only a single substrate is the precise match for the enzyme. Once the enzyme finds its exact counterpart, the chemical reaction can begin.
What is the induced fit model?
The induced-fit model is generally considered the more correct version. This theory maintains that the active site and the substrate are, initially, not perfect matches for each other. Rather, the substrate induces a change of shape in the enzyme creating an even tighter fit than before.
How can the evidence for the induced fit model be created?
Through crystallising enzymes before and after being bound to a substrate in order to see if the shape has chnanged.
What type of energy is used to catalyse the reaction?
Enzyme-substrate binding energy, soenergy gained from bringing the reactants together which is also known as approximation. This can increase the rate of reaction.
What can the binidng enery do?
- Increase the rate of reaction
- Constrain the movement of the substrate when it is bound
- Stabilise positive and negative charges in t-state (this means that the enzyme will have residues which neutralise the charges that pop up during transition)
What other method are enzymes able to do in order to speed the rate of the reaction up?
They can find an alternative reaction pathway which requires less energy, which means that more molecules are able to to have required activation energy and thus more frequent collisions and then an increase in the frequency of successful collisions, so a faster rate of reaction.
Why is it useful for the enzyme to strain bonds within the enzyme?
By straining particular bonds within the enzyme as well as lowering the activation energy needed, it makes it easier for the substrate to be broken down since straining the bonds can distort the shape of the substrate into its transition state.
What can enzymes use to help bring substrates to its active site?
Co-factors.
What can enzymes exclude from its active site to make the reaction of breaking down the substrate faster?
Solvents.
What is reaction velocity?
The rate at which products are made from the substrate.
What is Vmax?
It is the maximum possible velocity when all active sites are occupied- this can be represented on a graph where the curve plateaus off.
What is Vmax2?
The maximum possible velocity when half of all active sites are occupied - this is exactly half of the Vmax.
What does it mean when on a velocity concentration graph’s line plateaus off?
It shows that the limiting factor are the active sites, as there is a limit to how much it can increase by.
What is Km?
It is the amount of substrate that you would have to put in to half saturate the active site (this helps to show the binding affinity of the enzymes).
What is the formula for the enzyme reaction (Michaelis-Menten equation)
E + S ↔ ES ↔ E + P
Where E is the enzyme, S is the substrate, ES is the enzyme-substrate complex, and P is the product.
