ENZYME QUESTION - 1988			L. PETERSON/AP BIOLOGY
  	After an enzyme is mixed with its substrate, the amount of product formed is   
  	determined at 10-second intervals for 1 minute. Data from this experiment 
  	are shown below.


	Time (sec)		0	10	20	30	40	50	60
	Product formed (mg)     0.00       0.25        0.50        0.70       0.80       0.85        0.85

	Draw a graph of these data and answer the following questions.
	a. What is the initial rate of this enzymatic reaction?
	b. What is the rate after 50 seconds? Why is it different from the initial rate?
	c. What would be the effect on product formation if the enzyme were heated to a 
    	     temperature of 100 oC for 10 minutes before repeating the experiment? Why?
	d. How might altering the substrate concentration affect the rate of the reaction? Why?
	e. How might altering the pH affect the rate of reaction? Why?

 
  STANDARDS:
    maximum points = 10
  
  DATA RECORD AND CALCULATIONS
    GRAPH           axis X = Time (ind); Y = Product (dep)  3 pts
               scale and label axis
               curve plotted - drawn curve necessary
    a.  initial rate          1 pt. setup (.25-.00)/(10-0)  2 pts
         0.025 mg/sec              or    (.50-.00)/(20-0)
            .25  mg/10 sec           or    number 0.025
           1.5   mg/min  1 pt. units (mg/sec) or mg/min)
           1/40 mg/sec
    b.  rate after 50 sec                                   1 pt
     Zero      1 pt. set up (.85-.85)/(60-50)
                      or      1 pt. units if not awarded in part a.
     net rate
     equilibrium
  
     Why?                                    1 pt
       Substrate gone or reaction at equilibrium
       Other explanation - any are possible
          Product inhibition
          Product changes pH or temp optimum
          Product release time varies             Maximum = 7 pts
  
  EXPLANATIONS:
  c. Temperature variation
     Change: stops reaction; no product formation;          1 pt
          rate near or at zero
     Explanation: Conformational shape change - denaturation     1 pt
          (inactivation - "kills" in quotes)
  
  d. Substrate concentration variation;
     Change:                                 1 pt
          (Increase) a) no change, initial slope same;
                      longer to level off;
                      or b) increase in reaction rate
          and/or
          (Decrease) more gentle slope; decrease rate or take less time to level off;
     Explanation:                            1 pt
          (Increase) a) Enzyme is working as fast as it can (Vmax)
                        or b) It will approach Vmax
          or
          (Decrease) Enzyme no longer saturated; or further from saturation;
  e. pH variation
     Change:                                 1 pt
          a) Slight change may affect the curve either way
          b) Drastic change may stop the reaction
     Explanation:                            1 pt
          a) Enzyme has optimum pH
          b) Enzyme can be denatured by extremes
                                        Maximum = 6 pts