MCBG Session 3 - Enzymes Flashcards
What is the function of an enzyme and how does it achieve this?
- To alter the rate of a reaction
- By providing an alternative pathway for the reaction with a lower activation energy (more molecules have sufficient energy), therefore accelerates the attainment of equilibrium.
What are the key features of the ‘active site’ of the enzyme?
- Only occupies a small part of the enzyme
- Formed by different AA’s of the primary sequence (don’t have to be adjacent)
- Tend to be in clefts/crevices (to exclude water)
- Substrates bind weakly so that products can be readily released.
What is the rate of a reaction of enzyme activity dependent on?
The substrate concentration.
What is the Michaelis-Menton equation?
What is this equation telling us?
Vo = Vmax x (S)/Km + (S)
- Vmax = maximum velocity (mol/min)
- S = substrate concentration (mol)
- Km = substrate concentration at half Vmax
Vo = velocity of reaction in standardised rate, e.g.: Per L, Per g of tissue etc.
- Telling us that rate of reaction is proportional to substrate concentration.
How do you turn a Michaelis-Menton plot into a straight-line form?
Take double reciprocals and create Lineweaver-Burk plot.
What is the difference between competitive and non-competitive inhibitors?
Competitive = Binds to active site, competes with substrate to reduce mount of ES complexes
competitive = Bind elsewhere, reduces concentration of functional enzyme (stops substrate binding)
How can we distinguish between competitive and competitive inhibitors? (describe in terms of Km + Vmax)
- Effect of competitive inhibitors can be overcome by adding more substrate to outcompete inhibitor, therefore Km increases, Vmax stays the same.
- Adding more substrate in a non-competitive inhibitor will not overcome effect, therefore Km is unaffected, Vmax decreases.
Note - need to be able to describe how rates of reaction vary as a function of enzyme and substrate concentration on simple velocity vs (S) graphs - see group-work for examples.
Ez.
