enzymes Flashcards
what are enzymes? what bonds are they held in place by?
enzymes are globular proteins that are folded together into a precise 3D shape held by hydrogen bonds, ionic bonds and disulphide bonds
what can enzymes affect?
functions and structures in an organism
what do enzymes lower?
activation energy
what forms when enzyme and substrate react?
enzyme-substrate complexes
what is denaturing?
when a protein changed shapes it can’t function. This is caused by changes in temp or pH. Changes in temp break the weak hydrogen bonds in the secondary and tertiary structures. Changes in pH break the ionic bonds in the tertiary structure
what is the lock and key hypothesis?
Enzymes only work with substrates that fit their active sit. Specific substrates only fit specific active sites like specific keys only fit specific locks. They are complemetary to each other
what is the induced fit model?
This model takes into account the more complex action of the enzyme. When the substrate binds to the AS, the enzyme changes shape slightly to fit the substrate. This distorts the substrate molecule, putting stress on the bonds and reduces the amount of energy needed to break or form bonds, lowering the AE.
how can you measure enzyme activity?
how fast the substrate is broken down
how fast the product is made
what is the enzyme shape determined by?
tertiary structure
how does low temp affect enzymes?
at low temps, enzymes have too little KE so there’s few successful collisions between enzymes and substrates which leads to low rate of reaction.
how does low pH affect enzymes?
acidity breaks the bonds and the active site is denatured
how does substrate concentration affect enzymes?
increasing substrate concentration increases number of collisions. Eventually the substrate concentration will be high enough to fill all active sites. ATP, maximum rate has been reached and increasing concentration won’t make a difference
how does enzyme concentration affect enzymes?
at low EC, theres more competition for AS’s. As EC increases, there’s more collisions ‘’ a faster rate. Rate off reaction is directly proportional to EC. Eventually, substrate concentration becomes a limiting factor and increasing EC has no effect
what happens to the enzymes at optimum temp?
the enzymes move quickly and there’s the highest number of successful collisions. Highest rate of reaction.
what happens to the enzymes at high temps?
heat breaks the hydrogen bonds maintaining the tertiary structure and the AS becomes denatured
how does high pH affect enzymes?
alkalinity breaks the ionic bonds and the AS is denatured . No successful collisions.
what happens to enzymes at optimum pH?
the optimum pH is dependent on the type of enzyme and location. At the optimum, there’s the most collisions and the highest rate. If pH changes too much, the chemical nature of the amino acids can change. This can change the bonds that hold the 3D structure
what are competitive inhibitors?
molecule with a similar shape to substrates and bind to the active sit which stops the substrates from binding. This reduces the number of ES complexes. They are non permanent so eventually it will leave the AS and a substrate can fit. An increase in SC will reduce the effect.
what are non competitive inhibitors?
bind to the enzyme and change its shape. This is known as allosteric inhibition. The substrate no longer fits so the enzyme cant function. The inhibitor prevents normal ES complexes being formed. The rate is reduced. They don’t compete with substrates as they are a different shape and don’t bind to the AS
what is a catalyst?
a substance that speeds up a chemical reaction without being used up itself
what are the 2 models of enzyme action called?
induced fit, lock and key hypothesis
what do enzymes catalyse?
metabolic reactions
why are enzymes highly specific?
because of their tertiary structure and only one complementary substrate will fit into the active site
what is an enzymes active site determined by?
its tertiary structure
