Enzyme Kinetics Flashcards
What does enzyme kinectics describe in mathmatical terms?
The rate of an enzyme reaction.
In enzyme kinetics, what does S stand for?
Substrate concentration.
In enzyme kinetics, what does Vo stand for?
The rate of enzyme reaction.
What can be measured by adding a fixed amount of an enzyme to tubes of containing a range of substrate concentrations and measuring the rates of product formation / substrate depletion?
The rate of enzyme reaction.
How can the rate of enzyme reaction be measured?
The rate of enzyme reaction can be measured by adding a fixed amount of an enzyme to tubes containing various concentrations of substrates and following the rate of product formation / substance depletion.
At equilibrium, what proportion of the enzyme is reacting?
All of it!
As time goes on and …………. product is produced, there are …………. susbstrate molecules for …………… to react with, so the ………………… of the reaction changes over time.
More, less, enzymes, kinetics.
What must an enzyme-substrate complex be, in order for the reaction to work?
Stable.
What does ‘rate constant’ (K) describe?
The likelihood of a reaction happening.
What does the Michaelis-Menton equation show?
Vo = Vmax x [s] / Km + [s]
The Michaelis Menton equation shows the concentration of substrate needed to reach half of the maximum speed of the reaction.
What does K stand for?
The rate constant - the likelihood of a reaction happening.
What is this equation? What does it show?
Vo = Vmax x [s] / Km + [s]
This is the Michaelis-Menton equation, which shows the concentration of susbstrate needed to reach half of the maximum reaction velocity.
True or false? The Michaelis-Menton equation can be represented by a graph.
True.
The graph represents the concentration of substrate (Km) required to reach half of the reaction’s maximum velocity (V max / 2).
What equation is this? Which equation is it a rearrangement of?
1/Vo = 1/Vmax + Km/Vmax x 1/[s]
This is the Lineweaver-Burke equation, which is a rearrangement of the Michaelis-Menton equation.
What does a Lineweaver-Burke graph show? Why?
A Lineweaver-Burke graph shows the gradient of the curve in a Michaelis-Menton graph.
It was used to calculate rates of reaction before computers, as it results in a straight line which is easier to read than a curve!
What does the following describe?:
‘the maximum catalytic rate when substrate is not limiting. All the enzyme is in the enzyme-substrate complex. The enzyme is said to be saturated’.
Vmax.
If Km is half of Vmax, what does it show? How can this be used?
Km shows an enzyme’s affinity for a substrate.
Substrate concentrations can be modulated to predict what is (or is not) being taken up.
When a competitive inhibitor is added to a reaction, where would the line for the reaction with the competitive inhibitor cross the y-axis (1/v) of a Lineweaver-Burke graph, compared with the line for the reaction without the inhibitor?
What does this show about the Vmax?
The lines would cross the y-axis at the same point, whether the competitive inhibitor is present or not.
This means that the Vmax does not change when a competitive inhibitor is present.
When a non-competitive inhibitor is present, where would the line for the reaction with the noncompetitive inhibitor cross the x-axis (1/v) of a Lineweaver-Burke graph, compared with the line for the reaction without the inhibitor?
What does this show about the Km?
The lines cross the x-axis at the same point whether the non-competitive inhibitor is present or not.
This shows that the Km does not change when a non-competitive inhibitor is present.
When a competitive inhibitor is present, does the Vmax or the Km change?
The Vmax stays the same in the presence of a competitive inhibitor, the Km changes.
When a non-competitive inhibitor is present, does the Vmax or the Km change?
The Km stays the same when a non-competitive inhibitor is present. The Vmax changes.
What role does the enzyme chymotrypsin play in the digestion of proteins?
Chymotrypsin braks down larger peptides into smaller ones, working from the outside in.
Where on large, hydrophobic amino acids does chymotrypsin work?
Chymotrypsin cleaves peptide bonds on the carboxyl (COOH) side of large, hydrophobic amino acids such as tyrosine, tryptophan, phenylalanine and methionine.
True or false? Enzymes (e.g. chymotrypsin) can reform and repeatedly catalyse a reaction, regenrating itself until it is degraded or the reaction is inhibited.
True.
What is substrate specificity?
An enzyme only works on a specific substrate, even at a certain bond within a molecule.
