Lab 2 Flashcards
What does Beer’s Law state?
The concentration of a solution is proportional to the absorbance of that solution
5% beeeeeeeeeeeersssss
What does Lambert’s law state?
The intensity of the absorbance is proportional to the path length
- The intensity of transmitted light decreases exponentially when path length increases
What is the molar absorption coefficient (ε) a measure of?
How strongly a chemical absorbs light at a particular wavelength. At a particular wavelength for a particular molecule this will be a constant value.
What is the path length (NOT wavelength) of a standard cuvette?
1cm
When plotting an absorbance vs. concentration graph what relationship should be observed?
A linear relationship as absorbance and concentration are proportional (Beer’s law). This is shown as a standard curve.
What does the Beer-Lambert law state?
That concentration and path length are two variables that affect an absorbance reading at a specific wavelength
What are the units of the molar absorbance coefficient?
L.mol-1.cm-1 or L/mol.cm
What is alcohol dehydrogenase (ADH) and why does it need to be kept on ice?
It is an enzyme which breaks down primary alcohols into aldehydes e.g. ethanol is oxidised to acetylaldehyde. It is involved in redox reactions so it needs a coenzyme e.g. NAD+ is reduced to NADH/H+.
It needs to be kept on ice to prevent the loss of enzyme activity.
What is an absorbance spectrum used for?
To plot the absorbance across different wavelengths. The absorbance spectrum shows which wavelengths are absorbed more than others.
Which equation is used when finding the initial velocity from a absorbance vs time progress curve and what are the units?
V = change in absorbance/change in time
V = A end - A start/ Time end - Time start
Units for velocity: A.min-1
For which experiment is it assumed that the reaction goes to completion?
When using enzyme assays to analyze complex solutions for specific molecules.
What happens when enzyme concentration is decreased in an assay?
It decreases the initial rate of reaction Lowering enzyme concentration reduces the number of active sites available for catalysis.
Is the reaction rate of an enzyme catalysed reaction independent of substrate concentration when the reaction rate is first-order?
No, in first order the reaction rate is directly proportional to the substrate concentration. The reaction rate becomes independent of substrate concentration at zero-order kinetics.
Velocity is proportional to ____ ______ at saturating substrate concentrations.
enzyme concentration
____ ______ can be varied to determine the V max of an enzyme catalysed reaction.
substrate concentration
