RP1- effect of variable on enzymes

Question 1

Examples of variables that affect rate of reaction

Answer 1

-Enzyme concentration/ volume
-Substrate concentration/ volume
-Temperature of solution
-pH of solution
-Inhibitor concentration

Question 2

How temperature can be controlled?

Answer 2

-Use a thermostatically controlled water bath
-Monitor using a thermometer at regular intervals and add hot/ cold water if temperature fluctuates.

Question 3

How pH can be controlled?

Answer 3

-Use a buffer solution
-Monitor using a pH meter at regular intervals.

Question 4

Why enzyme and substrate solutions left in water bath for 10 minutes before mixing?

Answer 4

-So solutions equilibrate/ reach the temperature of the water bath

Question 5

Describe a control experiment

Answer 5

-Use denatured enzymes.
-Everything else same as experiment- same conc/ volume of substrate and enzyme, same type/ volume of buffer, same temp

Question 6

How can ror be measured?

Answer 6

-Measure time taken for reaction to reach a set point.
-Plot graph of time against volume.
-Draw tangent at t=0
-Initial rate of reaction

Question 7

Suggest a safety risk and explain how to reduce this risk?

Answer 7

-Handling enzymes may cause an allergic reaction
-Avoid contact with skin by wearing gloves and eye protection

Question 8

Explain why using a colorimeter to measure colour change is better than comparison to colour standards.

Answer 8

-Not subjective
-More accurate

Question 9

Explain a procedure that could be used to stop each reaction.

Answer 9

-Boil/ add strong acid/ alkali- denature enzyme.
-Put in ice- lower KE so no ES complexes form.
-Add high conc of inhibitor- no ES complexes form.

Question 10

How processed data can be presented as a graph?

Answer 10

-Label x-axis with independent variable and y-axis with rate of reaction.
-Plot a linear scale on each axis that will allow the graph to occupy over half available space.
-Mark data point with crosses.
-Join data points by straight lines if intermediate values are not known OR draw line/ curve of best fit.

Question 11

Explain why the ROR decreases over time throughout each experiment?

Answer 11

-Initial rate is highest as substrate conc not limiting/ many ES complexes form.
-Reaction slows as substrate used up and often stops as there is no substrate left.