Enzymes
Essay Preview: Enzymes
Report this essay
Enzymes
CHARACTERISTICS
Molecule has a active site
Changes in ph and temperature can adversely change enzyme action
Increase rate of reaction i.e. acts as a catalyst
All processes are reversible
Protein molecules well developed tertiary structures
Specific
Remember in order to start a reaction a certain amount of energy has to be supplied called activation energy.
STRUCTURE
Enzymes are globular proteins; this means they are very complex
LOCK AND KEY
The enzyme provides the substance with a specific part where it can fit to form an enzyme substrate complex.
INDUCED FIT
Shows that the enzyme-substrate complex as being more flexible – in that the substrate molecules changes shape of enzyme molecule as the enzyme substrate complex formed.
HOW THEY WORK?
There is similarities between enzyme and the active site
Electrostatic bonds used to establish the enzyme substrate complex.
Some enzymes have non-protein parts which are necessary for enzyme action
These are called Co-factors, which are three of them inorganic ions. Prosthetic groups and co-enzymes
WHAT IS A CO-FACTOR?
Some aspect over and above the enzyme which is needed for the enzyme to work
In some cases: enzyme + co-factor are needed for enzyme action.
INORGANIC IONS
Around the enzymes helps do its job
They mainly influence shape of enzyme molecule e.g. Cl‾ is needed for salivary amylase. Many trace elements can fulfil its role e.g. Zinc, Copper.
PROSTHETIC GROUPS
Similar to co-enzyme
Usually act as carriers during enzyme controlled metabolic change
CO-ENZYMES
Very similar but loosely attached to the enzyme molecule
TEMPERTURE
If temperature goes above a certain level the vibration will break some of the bonds that hold the enzyme
Active site changes so no longer fit
At this enzyme denatures
GRAPH OF RATE OF REACTION
The steep declines after an optimum
At low temperatures, enzymes are inactivated rather then denatured ( the extent is dependent on time)
In enzyme experiments, remember technique of equilibration i.e. allowing enzyme & substrate to reach a desired temperature separately.
PH AND ENZYME ACTION
Shape of graph is symmetrical, more bell- shaped.
WHY? HOW? Does PH affect enzyme activity?
Ph affects the ionisation of side groups in amino acid residue
In extreme case Ph can denature enzymes
Can switch it on of off as sometimes enzymes not surrounded by its optimum temperatures
SUBSTRATE CONCENTRATION ON RATE OF ENZYME ACTION
Affects the rate of reaction up to certain point
The higher the substrate concentration the faster the reaction but only up to saturation point
After that there is too much substrate molecules enzyme can cope with.
REVERSIBLE INHIBITION
This is when inhibition may be easily removed
Competitive reversible inhibition. This is described as active site directed inhibition. Here there is shape similarities between substrate and the inhibitor, they are so similar that the inhibitor occupies the active site prevents the substrate from doing so and therefore lowers the rate.
How could you reduce the affect of active site directed inhibitor? By increasing the concentration of true substrate.
Non competitive or non active site directed inhibition
Inhibitor binds to the allosteric site (alternative site) changing shape of active site.
INCREASED ENZYME CONCENTRATION
The more enzyme molecule, the more likely the substrate is to collide. So increases in rate.