Biology RP1

Factors affecting the rate of an enzyme-controlled reaction.

Name six factors that will affect the rate of an enzyme-controlled reaction.

• Temperature.

• pH.

• Enzyme concentration.

• Substrate concentration.

• Presence of competitive/non-competitive inhibitor.

• Concentration of inhibitor.

What is the dependent variable of this investigation?

The rate of reaction.

Give three ways in which the rate of a reaction could be measured and an enzyme-controlled reaction that these dependent variables apply to.

• Time taken for a reaction mixture to turn cloudy (trypsin hydrolysing protein into peptides).

• Volume of gas produced in a given amount of time (catalase hydrolysing hydrogen peroxide into water and oxygen gas).

• Time taken for a certain colour change to take place (amylase hydrolysing starch in the presence of iodine solution).

What equipment might you need for an investigation where you are measuring how temperature change affects the rate of an enzyme-controlled reaction?

• Water baths of different temperatures.

• Boiling tubes.

• Tongs.

What equipment might you need for an investigation where you are measuring the volume of gas produced?

• Water trough.

• Measuring cylinder.

• Conical flask with bung attached to delivery tube.

OR

• Conical flask with bung.

• Gas syringe.

How do you work out the uncertainty of a piece of equipment?

Get the resolution of the equipment. Divide the resolution by two, this is the uncertainty.

What would the uncertainty of a thermometer with a 1 degree celsius resolution be?

+ or - 0.5 degrees celsius.

What type of graph would you draw if your independent variable is continuous?

Line graph.

Give five examples of continuous independent variables.

• Temperature.

• pH.

• Enzyme concentration.

• Substrate concentration.

• Inhibitor concentration.

What sort of graph would you plot if your independent variable was categorical?

Bar chart.

Give one example of a categorical independent variable in this investigation.

• Use of competitive/non-competitive inhibitor.

On which axis do the independent and dependent variable go on a graph?

Independent variable on the x-axis, dependent variable on the y-axis.

Describe and explain how increasing temperature affects the rate of an enzyme-controlled reaction.

At the start, increasing the temperature increases the rate of reaction as the enzyme and substrate molecules have more kinetic energy so the frequency of collisions forming enzyme-substrate complexes increases. Once the temperature increases past the optimum, the rate of reaction decreases as the enzymes start to denature meaning they are no longer complementary to the substrate so less enzyme-substrate complexes can form.

Describe and explain how increasing enzyme/substrate complex affects the rate of an enzyme-controlled reaction.

At the start, increasing enzyme/substrate concentration increases the rate of reaction as there are more enzyme/substrate molecules for substrate/enzyme to collide into and form enzyme-substrate complexes. However, eventually increasing the enzyme/substrate complex will no longer increase the rate of reaction as the substrate/enzyme concentration becomes the limiting factor.

Give three possible hazards you could find in this investigation, give a risk and safety precaution for each hazard.

• Hazard: broken glass, risk: cuts, safety precaution: be careful handling glass objects/ don’t place glassware near the edge of the worktop.

• Hazard: enzymes, risk: allergies, safety precaution: wear eye protection/ wear gloves/ avoid direct contact with skin.

• (If investigating temperature) hazard: hot liquids, risk: scalding, safety precaution: use tongs to remove boiling tubes from water baths.