Energy and Enzymes

exergonic reaction

energy moving outward

endergonic reaction

energy moving inwards

when the gibbs free energy is negative, it is a…

spontaneous reaction

when the gibbs free energy is positive, it is a…

non spontaneous reaction

spontaneous process definition

a process that can occur without energy input

exergonic reaction example (in plants)

cell respiration

example of endergonic reaction (in plants)

photosynthesis

difference between endergonic reactions and exergonic reactions (spontaneity)

exergonic reactions are spontaneous, endergonic reactions are not spontaneous

activation energy

the amount of energy needed for a reaction to take place

effect that enzymes have on activation energy

they lower the activation energy barrier

effects enzymes don’t have on reactions

they cannot change the free energy, they cannot make endergonic reactions exergonic

the reactant an enzyme acts on:

substrate

process of enzyme reaction in order

enzyme plus substrate, enzyme substrate complex, enzyme and product

active site

region of the enzyme where the substrate binds to

reason for enzyme specificity

complimentary fit between the shape of the active site and the shape of the substrate

lock and key hypothesis

the substrate must fit in the active site in order to form the enzyme-substrate complex

induced fit model

the substrate is not a perfect fit to the active site, so the enzyme slightly changes its shape when it bonds with the substrate

2 weak chemical bonds that hold enzymes in the active site

ionic bonds and hydrogen bonds

saturated enzyme

when all active sites of an enzyme are occupied by substrate molecules, enzyme is working at maximum capacity

factors that affect enzyme functions

temperature and pH

optimal conditions

conditions that favour the enzyme

optimal temperature range for most enzymes

35 to 40 degrees celsius

optical pH range for most enzymes

6 to 8

effect of enzymes having the wrong pH/temperature

they become denatured, change shape and lose their function

cofactors

nonprotein helpersfor chemical processes that cannot easily be carried out by the amino acids in proteins.

example of chemical processes that cofactors are used for

electron transfers

coenzyme

cofactor that is an organic molecule

competitive inhibition

inhibitors that mimic the subtrate and compete with it for the active site

solution to counteract competitive inhibitors

increase the concentration of substrates

non competitive inhibition

inhibitor binds to another part of the enzyme, causing it to lose its shape and lessen effectivity

pros of selective inhibition

controls cellular metabolism by regulating enzyme activity

allosteric regulation

a regulatory molecule binds to a different site than that of the substrate, can cause inhibition or stimulation of the enzyme’s activity

cooperativity

substrate molecule binds to site in multisubunit enzyme, triggers a change in all units, amplifies response of enzymes to substrates

end product/feeback inhibition

an enzyme that catalyses one of a series of reactions is inhibited by the ultimate product of the pathway