enzymes 2.10, 2.11, 2.12, 2.13 & 2.14B Flashcards
what are enzymes?
biological catalysts
what controls the chemical reactions in cells?
the group of proteins called enzymes
what is a catalyst?
a chemical that increases the rate of reaction without being used up in the reaction
increase rate of reaction by providing an alternate pathway with lower activation energy
how do enzymes work?
have: enzyme, substrate, active site
- substrate and enzyme collide
-substrate binds to active site of enzyme - enzyme-substrate complex
- after reaction the products do not fit active site shape (no longer complementary)
what affects the rate of enzyme?
temperature
adding more substrate or enzyme
how does high temperature increase rate of reaction (enzymes)?
as temp increases the enzyme and substrate have more kinetic energy, faster and there are more successful collisions
this occurs until the optimum temperature is reached
what can cause an enzyme denaturing?
high temperatures
changes of pH
active site so no longer complementary to substrate
substrate cannot bind to the active site
what does rate mean?
how many events happen in a given amount of time
how does pH affect rate of reaction?
pH inside cells is 7 (neutral) - most cells work best at this pH
if pH changes it can affect shape of enzyme, active site changes shape and no longer complementary to substrate, enzyme denatured.
practical: investigate how enzyme activity can be affected by changes in temperature.
investigate effect of amylase and how it digests starch
mix 10cm^3 of 10% starch suspension
5cm^3 of amylase in a boiling tube and heat in a water bath
every minute take a drop of the mixture and add a drop of iodine solution in spotting tile
when digestion is complete and no starch is present, iodine will stay orange (rather than turning black/blue)
repeat using different temperatures
practical: investigate how enzyme activity can be affected by changes in pH
potato contains enzyme catalase (which breaks down into hydrogen peroxide) forming water and oxygen
add 10 potato disks (1cm thick, cut with cork corker)
add to 20cm^3 of catalase
measure volume of gas produced in 5 minutes
pH altered by adding different volumes of a weak alkali (sodium carbonate) or weak acid (ethanoic acid)
use universal indicator paper to determine pH of solution