Module 2- Enzymes Flashcards
what is the role of an enzyme?
-biological catalysts
-increases rate of reaction by reducing Ea
-remains unchanged and reusable at the end of the reaction
what is an anabolic reaction?
requires energy, building up of simple molecules to form new molecules, required for growth
what is the lock and key hypothesis?
substrate has a spepecific+complementry shape to the active site
active site does not change shape to fit the substrate.
what is the induced fit hypothesis?
states active site is flexible and changes shape to mold around substrate as it binds-closer fit
how does the ESC increase rate of reaction?
initial interaction of enzyme + substrate is quite weak,,,weak interactions rapidly induce changes in tertiary structure of enzyme strengthening binding in ESC + strains substrate molecule,,, weakens bonding in substrate therefore lowering Ea
what is meant by specificity of an enzyme?
each enzyme catalyses 1 biochemical reaction
what enzyme catalyses hydrogen peroxide and is it intracellular or extracellular/
catalase- broken down into non toxic O and H2O before H2O2 can accumulate
intracellular
what is an intracellular enzyme?
acts within cells e.g. catalase
what is an extracellular enzyme?
secreted by cells and catalyse reactions outside cells
what enzyme catalyses starch and is it intracellular or extracellular?
amylase- catalyses starch into maltose
extracellular
what enzyme catalyses maltose?
maltase- catalyses maltose into glucose
why are different enzymes needed for digestion?
each enzyme only catalyses one specific reaction
what is trypsin?
a protease (enzyme that catalyses digestion of proteins into smaller peptides then amino acids by other proteases)
how does competitive inhibition work?
-inhibitor + substrate have complimentary shape to active site
-blocks substrate from entering active site + catalysing reaction
-enzyme is inhibited (cannot carry out function)
how do competitive inhibitors slow down rate of reaction?
-substrate + inhibitors in solution compete with each other to bind to active sites of enzymes catalysing reaction
-reduces amount of ESC formed in given time ∴ slowing down rate of reaction
what does the degree of competitive inhibition depend on?
relative concentration of inhibitor, substrate, enzyme
are all competitive inhibitors permanent?
most are temporary ∴ effect is reversible. exceptions include aspirin.
examples of competitive inhibition?
statins- competitive inhibitors of enzymes used in synthesis of cholesterol in the liver (helps reduce blood cholesterol concentration)
aspirin- irreversibly inhibits COX enzyme preventing synthesis of prostaglandins thromboxane (pain+fever causing chemicals)
what effect do competitive inhibitors have on rate of reaction?
reduces but does not change the maximum rate of reaction the enzyme inhibits
how does non-competitive inhibition work?
-inhibitor binds to enzyme at allosteric site
-binding of inhibitor causes tertiary structure of enzyme to change shape, including active site
-active site no longer complementary to substrate
-enzyme cannot carry out function because substrate cannot bind
-enzyme is inhibited
what is the allosteric site?
alternative site on enzyme to active site
what effect does non-competitive inhibition have on rate of reaction?
-increasing concentration slows rate of reaction as less active sites become available,, fewer ESC
examples of non-competitive inhibitors?
Proton pump inhibitors (PPIs)- used to treat long term indigestion,,,irreversibly blocks enzyme system responsible for secretion of H+ in stomach ∴ recuses production of excess acid which leads to stomach ulcers
what is end-product inhibition?
enzyme inhibition which occurs when end product of reaction acts as an inhibitor for enzyme that produced it– non-competitive reversible inhibition
what is the effect of low pH on enzyme activity?
-Hydrogen ions attract the negative r-groups in hydrogen and ionic bonds which causes them to break
-this changes the tertiary structure of the enzyme ∴ the active site is no longer complimentary to the substrate ∴ fewer ESC are formed ∴ decreasing rate of reaction
what is the effect of high pH on enzyme activity?
same of low pH except hydroxide ions attract positive r-groups in hydrogen and ionic bonds
what is the effect of high temperature on enzyme activity?
the enzyme and substrate gain KE ∴ there are more successful collisions between substrate and active site ∴ more ESC
what is the effect of high temperature after the optimum temperature?
-after optimum temperature due to gaining lots of KE the enzymes vibrate more causing strain on the bonds in tertiary structure of the enzyme and breaking these bonds∴ the active site is no longer specific to the substrate ∴ less ESC formed
-causes irreversible damage to active site
-enzyme becomes denatured
how does increased substrate concentration effect rate of reaction?
more successful collisions between enzyme and substrate ∴ more ESC are formed until all active sites have become saturated so enzyme concentration becomes limiting factor
how does enzyme concentration effect rate of reaction?
more successful collisions between enzyme and substrate ∴ more ESC are formed until all substrate is used up so substrate concentration becomes limiting factor
what is the temperature coefficient?
Q₁₀=R₂/R₁
whats the difference between a cofactor and a coenzyme?
cofactors are inorganic molecules whereas coenzymes are organic molecules
what is the chloride ion (Cl-) a cofactor for and what does it do?
amylase,, forms a correctly shaped active site
what are many coenzymes derived from?
vitamins via someones diet as they are organic molecules
what is a cofactor/coenzyme?
non-protein components necessary for the effective functioning of an enzyme,, bound loosely to the protein
what is the role of prosthetic groups in enzymes?
tightly bound to the protein to form a permanent feature on the protein
what is the prosthetic group for carbonic
anhydrase?
Zn2+
how can you measure the rate of reaction using hydrogen peroxide and catalase?
measure the volume of oxygen gas produced in a given time
what are the hazards in the hydrogen peroxide catalase practical?
-hydrogen peroxide is an irritant,, wear eye protection + avoid contact with skin
-take care in handling hot water baths
