Investigating Enzyme Action

Candidates should be able to: (a) state that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms; (b) state that enzyme action may be intracellular or extracellular; (c) describe, with the aid of diagrams, the mechanism of action of enzyme molecules, with reference to specificity, active site, lock and key hypothesis, induced-fit hypothesis, enzyme- substrate complex, enzyme-product complex and lowering of activation energy; (d) describe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity; (e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally; (f) explain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions, with reference to both reversible and non-reversible inhibitors; (g) explain the importance of cofactors and coenzymes in enzyme-controlled reactions; (h) state that metabolic poisons may be enzyme inhibitors, and describe the action of one named poison; (i) state that some medicinal drugs work by inhibiting the activity of enzymes (HSW6a).

Can you give the how science works term described by each of these? 1.What you changed in an experiment 2.What you measured in an experiment 3.What you kept the same in an experiment 4.A measurement close to the true value 5.Where repeat results are very close in value to each other 6.The difference between the maximum and minimum values in a set of results 1.Independent variable 2.Dependent variable 3.Control variables 4.Accurate 5.Precise 6.Range (e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally;

2H 2 O 2 2H 2 O + O 2 catalyst The enzyme responsible for this, catalase, is found in many living things. How could the effect of temperature on catalase be measured? What would the variables be? What would need to be controlled? Why?

(e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally; 2H 2 O 2 2H 2 O + O 2 catalyst

(e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally;

What is the initial rate of this reaction? What is the rate after 40 seconds? What is the rate over the first minute Why does the rate change over time?

(e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally; What is the initial rate of this reaction? What is the rate after 40 seconds? What is the rate over the first minute Why does the rate change over time?

(a)award two marks if correct answer (12) is given -6/30 / 6/0.5 × 60; -12;[2] (b)assume candidates are referring to the initial rate unless otherwise stated. -concentration of, substrate / H2O2, molecules, high / higher at start; -more chance of, substrate/ H2O2, molecules entering active site; -all / most, active sites occupied;[3] [5]

(e) describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally;

What are the limitations of each method? How could each experiment be improved?

Metabolic pathways are sequences of enzyme controlled reactions where the product of one reaction is a substrate for another enzyme E1 E2 E3 E4

E1 E2 E3 E4

SUBSTRATEACTIVE SITELOCK AND KEYPRODUCT CATALYSTPROTEINAMINO ACIDACTIVATION ENERGY ENDOTHERMHYDROPHILICHYDROPHOBICGLOBULAR MONOMERSPOLYMERSVESICLESHYDROLYSIS INDUCED FITCOMPETITORINHIBITORTEMPERATURE CONCENTRATIONpHOPTIMUMDENATURE ENZYME- SUBSTRATE COMPLEX HYDROGEN BONDS COMPLEMENTARYMETABOLISM COMPETITIVEPROSTHETIC GROUP CO-ENZYMENON- COMPETITIVE Sort your cards into groups –any way you like, but you must be able to explain your choices!!