section 4: enzymes - topic 2: factors affecting enzyme activity Flashcards
what are the factors that affect enzyme activity?
temperature.
pH.
enzyme concentration.
substrate concentration.
why does the rate of an enzyme-controlled reaction increase when the temperature increases?
more heat means more kinetic energy, so molecules move faster. this makes the substrate molecules more likely to collide with the enzymes’ active sites. the energy of these collisions also increases, meaning each collision is more likely to result in a reaction.
what is the optimum temperature?
the temperature at which the rate of an enzyme-controlled reaction is at its fastest.
what happens if the temperature gets too high?
the reaction will stop. the rise in temp makes the enzyme’s molecules vibrate more, but if the temp goes above a certain level, this vibration breaks the weak bonds in the enzymes tertiary structure (hydrogen & ionic). the active site changes shape, thus the enzyme and substrate no longer fit together. at this point, the enzyme is denatured.
what is the temperature coefficient (Q10)?
shows how much the rate of a reaction changes when the temperature is raised by 10 degrees.
what is the equation for the Q10 value?
Q10 = R2 (rate at higher temp) / R1 (rate at lower temp)
what Q10 value do most enzyme-controlled reactions have?
around 2.
what is the optimum pH?
the pH at which the rate of an enzyme-controlled reaction is at its fastest.
what is the optimum pH for most human enzymes?
7.
what pH does pepsin work best at? and why is this good?
2.
this is useful because it’s found in the stomach.
what happens above and below the optimum pH?
the H+ and OH- ions found in acids and alkalis can break the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure in place.
this makes the active site change shape, so the enzyme is denatured.
why does increasing the concentration of the enzyme increase the rate of reaction?
the more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme-substrate complex.
what happens if the amount of substrate is limited?
there comes a point when there’s more than enough enzyme molecules to deal with all the the available substrate, so adding more enzyme has no further effect.
why does a higher substrate concentration mean a faster reaction?
more substrate molecules means a collision between substrate and enzyme is more likely, so more active sites will be occupied and more enzyme-substrate complexes will be formed.
what is/ happens at the saturation point?
at this point, there are so many substrate molecules that all the enzymes’ active sites are full, so adding more substrate makes no difference.
the enzyme concentration becomes the limiting factor.
