Chapter 2 Enzymes and Digestion:
Common Exam Questions and Model Answers
Explain why the rate of reaction of an enzyme controlled reaction increases as temperature increased up
to the optimum

Increase in temperature increases kinetic energy

Molecules more around faster

Increased number of collisions between enzymes and substrates

More enzyme-substrate complexes are formed

Increased rate of reaction (apply to the particular enzyme in question)
Explain why the rate of reaction of an enzyme controlled reaction decreases as temperature increases
past the optimum

Increase in temperature increases kinetic energy

Too much kinetic energy breaks hydrogen bonds

Enzyme becomes denatured

Shape of 3D tertiary structure is changed

Shape of active site is changed, substrate is no longer complimentary to active site

Enzyme substrate complexes can no longer be formed

Decreased rate of reaction (apply to the particular enzyme in question)
Describe a biochemical test for reducing sugars.
1. Add Benedicts reagent and heat
2. Red/Orange/Yellow/Green (colour)
Describe a biochemical test for non-reducing sugars.
1. Test for reducing sugars
2. Negative result (remains blue) add HCl and heat for 5 mins
3. Add NaHCO3 slowly
4. Restest this solution with Benedicts reagent and heat
5. Orange/Brown (colour)
Describe a biochemical test for proteins.
1. Add NaOH
2. Add CuSO4 and mix
3. Lilac (colour)