C enzymes Flashcards
why does the competitive inhibitor result in the same value for Vmax but higher value for Km?
- CI competes with the substrate for active site of the enzyme as it is structurally similar to substrate. Since more enzyme inhibitor complexes are formed per unit time at low substrate concentrations, Km is higher. At high substrate conc, the inhibitor has less effect and thus substrate outcompetes inhibitor therefore Vmas remains.
what is competitive inhibition?
competitive inhibitors are structurally similar to substrates and will bind to the active site of the enzyme and thus compete with the substrate for the active site, reducing the number of active sites available for the substrates to bind and form enzyme-substrate complex.
what is the effect of competitive inhibitor on Km and Vmax?
Km of the enzyme will increase, Vmax can be reached eventually at higher subs conc. when subs conc is low, it is more likely for the enzyme to collide with competitive inhibitor molecules and form enzyme-inhibitor complex. thus the active sites available for subs will decrease, decreasing rate of ES complex formed per unit time
what is non-competitive inhibition?
non-competitive inhibitors are not structurally similar to the substrate molecule and bind at a site away from the active site, the allosteric site. this interaction alters the specific 3D conformation of the enzyme molecule such that active site is DISTORTED and no longer complementary to substrate, thus not able to bind to subs properly OR subs can still bind but enzyme cannot convert it into product
what is the effect of non-competitive inhibitors on Km and Vmax?
Km remains unchanged since NCI do not compete with subs molecules for active site (affinity of subs for enzyme remains the same) + Vmax is lowered as NCIs reduce the number of functional enzymes thus Vmax will not be restored even if subs conc is increased
how does pH affect enzyme activity?
at optimum pH, all the ionic and hydrogen bonds between our groups of amino acids are intact. The active sites are complementary to the substrate molecule as such maximum number of enzyme substrate complex can be formed per unit time.
A slight change in pH from optimum pH will change the charge found on the acidic and basic R groups of amino acids and the active site, reducing the binding ability of substrate to the active site and hence the rate of formation of enzyme substrate complex will decrease
A drastic change in pH from optimum pH will disrupt the ionic bonds between the acidic and basic R groups of the amino acids and the hydrogen bonds between polar R groups. This distorts the 3D conformation of the enzyme. Thus the active site is distorted and no longer complementary to subs. As a result, ES complex cannot form and enzyme is said to be denatured.
how does temp affect enzyme activity?
At very low temperatures substrate and enzyme molecules have low kinetic energy. Thus they move very slowly and there are very few effective collisions between enzyme and substrate molecules that the rate of enzyme substrate complex formation is very low.
As the temperature increases to optimum temperature, the kinetic energy of molecules increases and molecules move faster. Thus there are more effective collisions between enzyme and substrate molecules. There is an increase in the number of enzyme substrate complex formed per unit time. also substrate molecules at higher energy levels have a higher probability to overcome the activation energy barrier and form products.
At optimum temperature maximum number of ES complex formed per unit time.
At temperatures slightly above optimum temperature, thermal agitation of enzyme molecules disrupts the weaker bonds such as hydrophobic interactions hydrogen bonds and ionic bonds. This distorts the enzyme specific 3-D confirmation thus the active site is distorted and no longer complementary to the substrate. As a result substrate molecules cannot fit the active site of the enzyme molecules and ES complex cannot be formed. The enzymes are said to be denatured.
how does subs conc. affect enzyme acitvity?
At low subs conc, increase in subs conc increases the number of effective collisions between enzyme and subs. There is an increase in the no. of ES complex formed per unit time and hence a proportional increase in rate of formation of products. Subs conc is limiting.
At high conc, further increase in subs conc results in all active sites of enzymes being saturated with subs. Max no. of ES complex formed, rate of formation of products at maximum. other factors limiting.
how does enzyme conc affect enzyme activity?
At low enzyme conc, increase in enzyme conc increases the no. of active sites thus increases no. of effective collision between enzyme and subs. There is an increase in the no. of ES complex formed per unit time and hence a proportional increase in rate of formation of products. enzyme conc limiting
At high enzyme conc, substrate molecules not enough to occupy all active site. Max no. of ES complex formed per unit time hence rate of formation of products reached max. other factors limiting.
