CELL RESPIRATION QUESTION 1990:			L. PETERSON/AP BIOLOGY
 	The results below are measurements of cumulative oxygen consumption by 
	germinating and dry seeds. Gas volume measurements were corrected for
	changes in temperature and pressure.

				Cumulative Oxygen Consumption (mL)
  
	Time (minutes)	0	10	20	30	40
220 C  Germinating Seeds       0.0	8.8	16.0	23.7	32.0
            Dry Seeds		0.0	0.2	0.1	0.0	0.1
100 C  Germinating Seeds	0.0	0.0	0.2	0.1	0.2
            Dry Seeds		0.0	0.0	0.2	0.1	0.2	

	a.  Using the graph paper provided, plot the results for the germinating seeds 
	     at 220 C amd at 100 C.
	b.  Calculate the rate of oxygen consumption for the germinating seeds at 220 C,
	     using the time interval between 10 and 20 minutes.
	c.  Account for the differences in oxygen consumption observed between:
		(1) germinating seeds at 220 C and at 100 C.;
		(2) germinating seeds and dry seeds.
	d.  Describe the essential features of an experimental apparatus that could be 
	     used to measure oxygen consumption by a small organism. Explain why each 
	     of these features is necessary.


  STANDARDS:   Parts a, b, and c together = 8 pts MAX
          one point for each of the following:
  a.  GRAPH(S)
  ___Correct orientation of x (independent) and Y (dependent) axes
  ___Scale and label axes
  ___Curves plotted (both lines drawn and identified as 100/220). 
         Histograms accepted if correctly drawn.
  ___Title of graph
  b.  RATE CALCULATION
  ___Setup (16 - 8.8)/(20 -10) or number 7.2 or 0.72    
  ___Rate Concept - units (volume/time)
          7.2 mL/10 min. or 0.72 mL/min.
  c.  EXPLANATIONS
  1.  TEMPERATURE VARIATION
  ___Seeds show no temperature regulation (at environmental temperature);
         do not increase O2 consumption to maintain preset temperature
  ___Temperature increase causes increased activity 
     (or increased respiration or metabolism)
  ___Extended explanation of respiratory enzyme reaction rate, rate increases (to limit) 
         with increased temperature (enzymes generally have Q10 about 2.)
  ___220 vs. 100 rates reversed in cold hardiness (genetically determined) seeds
  2. GERMINATING SEEDS VS. DRY SEEDS
  ___Dry seeds dormant and/or germinating seeds metabolically active
  ___Extended explanation of dormancy and/or metabolism
  ___Explanation of water based chemistry of respiratory enzyme reactions
  
  d.  EXPERIMENTAL APPARATUS  3 pts MAX
  ___ Method to separate O2 consumption vs. CO2 release
          Something (KOH, etc.) to remove CO2 (gas -> solid)
  ___Closed System
  ___Method to measure pressure/volume change = graduated tube/pipet, 
          containing bubble/water/Brodie
  ___Method to control temperature = water bath
  ___Method to control volume = glass beads or some other inert material vs. seeds
  ___Timing device
  ___Equal numbers of organisms in experimental and control
  
  Other techniques/methods for measuring O2 consumption
     one point for any of the following:
  __ Winkler titration to determine O2 concentration before and after
  __ Polarographic, oxygen electrode, Clark-type electrode
  __EPR measurement of O2 concentration changes, in gas flow-thru system
  
     one point for a detailed explanation for any one of the above techniques
  
     None of these require special techniques to distinguish volume of CO2 from volume of 
     O2; all are specific for O2. None of these depend on pressure changes. Other features of 
     procedure (constant temperature, appropriate controls, etc.) remain the same.