Enzymes 1 & 2 Flashcards
Describe how enzyme differ from chemical catalysts.
Enzymes are able to catalyse very high reaction rates.
They show great reaction specificity.
They can work in mild temperature and pH conditions.
Enzymes can be regulated.
Name the 3 ways that enzymes catalyse reactions.
By lowering the activation energy due to;
1) Entropy reduction
2) Desolvation
3) Induced fit
Describe how enzymes catalyse reactions by reduction of entropy.
The enzyme can force the correct orientation of the substrate and active site, this lowers the activation energy of the reaction.
Describe how enzymes can catalyse reactions by desolvation.
The weak bonds between the enzyme and substrate replace most or all of the H bonds between the substrate and (aq) solution.
This ultimately lowers the activation energy of the reaction.
Describe how enzymes catalyse reactions by induced fit.
Conformational changes occur in the protein structure when the substrate binds.
This ultimately lowers the activation energy of the reaction.
Define the term ‘Michaelis constant’.
The Michaelis constant (Km) tells us how specific an enzyme is for the substrate.
A low Km = good fit.
A high Km = poor fit.
When the reaction is at half the maximum velocity, this means the substrate concentration is at Km.
Describe the molecular nature of competitive inhibition.
In competitive inhibition, the inhibitor binds to the active site, therefore blocking the active site to the substrate, this therefore means that there is more substrate needed and so there is an increase in Km.
However, the Vmax remains unchanged.
Describe non-competitive inhibition.
In non-competitive inhibition, the inhibitor binds to a secondary site, therefore causing a change in shape of the active site, meaning the substrate no longer fits. This causes the Vmax to decrease.
The Km remains unchanged.
Name a few reasons why measuring an enzyme may be important.
Detection of suspected disease at a pre-clinical stage.
Conformation of a suspected disease and assessing severity.
Localisation of disease to organs.
Characterisation of organ pathology.
Assessing response to therapy.
+ many more.
Name some factors that may affect enzyme activity.
Age
Gender
Pregnancy
Race
Time of day
Genetics
Drugs
Disease process, progress and treatment.
Name some factors that may trigger the release of enzymes.
Hypoxia
Microbiological agents
Cell damage
Genetic defects
Physical damage
Nutritional disorders
Immune disorders
Describe what ways in which enzymes can be analysed by rate of reaction.
The progress of the conversion of the substrate to product is monitored, in a fixed time manner, where the measurements are carried out at the end point.
Or in a continuous manner, where the measurements are carried out throughout.
Describe the analysis of enzymes using spectrophotometry and some problems associated.
Measurement of the end product by spectrophotometry, electrophoresis can determine type of enzyme.
Problems include:
Non-specific
Requirements of enzymes (temp, pH etc.)
Assays must be optimised for that enzyme.