Lec. 13 - Enzymes

Explain how enzymes increase the rate of biochemical reactions and three ways they do this.

they increase rate by lowering the activation energy needed to start the reaction: they bring substrates together in right position which stabilizes the transition state, and they create microenvironments for the reactions to occur

what CAN enzymes do?

speed up reactions by lowering activation energy, bind specific substrates to turn them into products, work repeatedly, control when and where reactions happen in a cell

what can enzymes NOT do?

change the overall deltaG of reaction, cannot change spontaneity of reaction, cannot provide energy

What is Vmax and what is it's significance?

it is the maximum rate of an enzyme catalyzed reaction when enzyme is fully saturated with substrate. important because it shows the enzyme's catalytic capacity/how fast it can work at full speed

What is Km and what is it's significance?

it is half of Vmax and it shows the enzyme's affinity for th substrate. low = high affinity and high = low affinity

what are the key factors that affect enzyme activity?

temp, pH, cofactors, and inhibitors, and substrate concentration

how does temperature affect enzyme activity

higher temp makes molecules move faster and more likely to hit one another. if too high, enzymes can denature

how does pH affect enzyme activity?

if enzyme is too acidic or too basic it will disrupt the ionic bonds.

how do cofactors affect enzyme activity?

cofactor= non-protein molecule or ion that some enzymes need to function (extra building block). if missing, enzyme can't function properly.

how do competitive inhibitors affect enzyme activity?

reduce productivity of enzymes by blocking substrates from entering active sites

how do non-competative inhibitors affect enzyme activity?

do not directly compete with substrate, but binds to other part of enzyme changing its shape so substrates can't react.

how does substrate concentration affect enzyme activity/rate?

the more substrate you have, the more reactions per minute

what is the transition state?

the time in a chemical reactions where the bonds of the reactants have broken, but the bonds of the products haven't formed yet

what is a phosphorylated intermediate?

the molecule that a phosphate group has temporarily attached to to make it higher energy so that molecule can more easily react.

define activation energy

the energy required to contort the reactant molecules so their bond can break

define enzyme substrate complex

when the enzyme has bonded to the substrate

define induced fit

when the enzyme hugs the substrate due to amino side chain interactions making the enzyme substrate complex.

what holds a substrate to an active site?

non-covalent interactions: hydrogen, ionic, van der walls

how does the enzyme lower the activation energy?

1- provides orientation to speed up reaction, 2- stretches and bends critical bonds (EA is proportional to difficulty of breaking bonds), 3- creating acidic pockets with R groups that can release H+ into the reaction to speed it up, 4) amino acids in enzyme can actively participate in reaction (creating temporaty covalent bonds between enzyme and substrate (enzyme returns back to original state after)