21. Most enzymes work by

A. increasing energy of activation
B. decreasing energy of activation
C. not affecting energy of activation
D. none of the above

22. Which category of enzymes belongs to class 5 in the international classification?

A. Hydrolases
B. Isomerases
C. Oxidoreductases
D. Cyclase

23. Lock and key theory is based on the compatibility of

A. enzyme and substrate
B. enzyme and product
C. enzyme and enzyme-substrate complex
D. enzyme-substrate complex and product

24. When an enzyme is functioning at V_max, the rate of the reaction is limited by

A. the number of collisions between enzyme and substrate
B. the number of substrate molecules in the reaction
C. the concentration of the substrate
D. the rate at which the enzyme can convert substrate to product

25. The equation for the rate of product formation for simple enzyme reaction is given by (Where r_max , maximum reaction rate, C_s substrate concentration, C_p product concentration ES, C_ES enzyme-substrate concentration)

A. r_p= r_max C_s/(K_m+C_s)
B. r_p= r_maxC_s/(K_m+ C_ES)
C. r_p= r_maxC_s/(K_m+C_ES)
D. r_p= r_maxC_s/(K_m+C_p)