D3 - factors affecting rate of reaction

Temperature

• increasing temperature increases enzyme activity

• more successful collisions

• rate increases until the optimum temperature is reached

• optimum temperature - enzyme activity is highest - human enzyme is 37 degrees

high temperatures

• too much heat breaks hydrogen and ionic bonds - holding the tertiary structure

• active site changes shape

• enzymes become denatured - irreversible

hypothesis for this:

• As the temperature increases, the rate of reaction of an enzyme also increases up until the maximum rate at the optimum temperature

• Above the optimum, as temperature increases, the rate of reaction decreases

• increased temperature means molecules have more kinetic energy, so there are more collisions between the active site and the substrate

• above optimum, enzymes denature so the active site changes shape and no longer binds to substrate and the rate of reaction decreases

Ph levels

• each enzyme has optimum PH - pepsin - PH 2

• as Ph increases, so does the rate of reaction

• hypothesis:

• excess H+ or OH+ ions disrupt bonding in the tertiary structure

• active site changes shape - loss of specificity

• Severe pH changes cause denaturation

• because further from optimum, more enzymes denature. This is because extreme PH breaks bonds in the enzyme and the active site changes shape, so no longer complementary to the substrate

substrate concentration

• decreased substrate concentration - not all enzyme molecules have substrate - rate is low

• increased substrate - more enzyme sub complexes form - rate increases

• high substrate concentration

• all active sites occupied - enzyme saturation rate reaches maximum and plateaus

hypothesis:

• As substrate concentration increases, the rate of reaction increases until, at high substrate concentration, the rate levels off at its maximum

• as substrate concentration increases, more successful collisions between the substrate and enzymes as - faster reaction

• The rate of reaction levels off when all the enzymes’ active sites are full. Adding more substrate will not make more enzyme-substrate complexes

enzyme concentration

• low enzyme concentration - fewer active sites - rate limited

• increasing enzyme concentration - more active sites - rate increases (linear)

limiting factor - eventually substrate runs out, rate plateaus

hypothesis:

• As enzyme concentration increases, the rate of reaction increases until the high enzyme concentration rate levels off at its maximum and plateaus

• This is because all the enzyme concentration increases, so there are more active sites to bind and form enzyme-substrate complexes - the rate levels off because all substrate molecules are bound and substrate concentration is now limiting.