Photosynthesis, Respiration, and the ATP-ADP Cycle

Clovis O. Price Jr.            Lucy Flower High School
                               3545 W. Fulton
                               Chicago IL 60624
                               (312) 535-6755 

Objective:

     The objective of this activity will be to demonstrate the three processes 
of photosynthesis, respiration, and the molecular interaction between ADP and 
ATP and the process by which they lose and gain phosphates in the process of 
energy conversion.  Students will learn about chloroplasts by the construction 
and labeling of a chloroplast; aerobic respiration in the mitochondria by the 
construction and labeling of a mitochondrion; and the chemical interaction of 
ADP and ATP by atomic modeling of ADP and ATP molecules as well as a game. 

Materials Needed:

    (5)  bags each of red beans, black beans, and lima beans. 
    (30) Ritter Dishes (clay planters/potting dishes)
    (30) pieces of construction paper (strips preferably)
    (5)  bags of potting soil
    (5)  containers of glue
    (5)  packages of thin tipped markers
    (5)  packages of thick tipped markers
    (10) packages of sponges (green, brown, and light green)
    (10) tennis balls
                                                            
Strategy:

     Photosynthesis consists of the absorption of light by chlorophyll pigments 
and conversion of this light to chemical energy.  This occurs in organelles 
called chloroplasts on membrane systems known as thylakoids.  Respiration 
reverses the process of photosynthesis, releasing the stored chemical energy.
Respiration occurs in organelles called mitochondria.  ATP consists of three 
parts, adenine, ribose, and (3) phosphate groups.  Adenine when bonded to ribose
gives us adenosine.  Adenosine plus three phosphate groups gives us ATP.  
Adenosine bonded to two phosphate groups is ADP.  In the energy production cycle 
in the chloroplasts and mitochondria, energy is stored when ATP is produced from 
ADP and a phosphate group "P". 

     The ATP/ADP cycle provides energy for cellular activity.  When energy is 
necessary the third phosphate group breaks off from ATP.  This forms ADP and 
releases energy. When a phosphate group is freed up, it may move on to another 
molecule in a process called phosphorylation.  The molecule gains both the 
phosphate group and the energy.  ATP synthesis is catalyzed by ATP synthetase.  
Photosynthesis, respiration and ATP/ADP are related.  Photosynthesis stores 
energy, respiration releases it, and ATP is the central molecule in this 
process. 

     The students will use the thin markers to mark the chemical symbols for 
each of the ADP/ATP chemical components on the surface(s) of the beans. There 
will be (1) chemical symbol marked on each bean.  Red beans may be used to 
represent the carbons, lima beans to represent the hydrogens, black beans to 
represent oxygens, and white beans to represent the nitrogens; long grain rice 
will be used to represent the single and double bonds.  After the beans are 
marked, they will be chemically arranged to represent the structures of the  
ATP/ADP molecules.  The beans will be glued to a sheet of construction paper. 
After the glue has dried, the construction paper with the beans will be placed 
in a Ritter dish.  The Ritter dishes will be at least half filled with soil and 
watered. The germination of the beans will occur within a few days.  This 
germination is followed closely by the beginning of the photosynthetic process 
which we have been studying. 

     The students will each be issued 1-2 sponges.  The students will carve the 
sponges into chloroplasts.  The residual sponge will be used create the 
thylakoids.  Half beans will be used to represent ATP synthetase molecules.  A 
similar activity can be used to create models of mitochondria.

     Using tennis balls the students will play a game of catch to demonstrate 
the loss of 1 phosphate to form ADP from ATP and the gain of one phosphate to 
form ATP from ADP.  The first toss will represent ATP to ADP; the return toss 
will represent ADP to ATP and so on.  The process (the game of catch) will be 
repeated until the students have clearly demonstrated their knowledge of the 
phosphate loss, phosphate gain process. 
  
Performance Assessment:

     Students should be able to explain the ADP/ATP cycle with 90-95% accuracy 
after they have completed both components of the exercise.  Students should be 
able to relate the process directly and indirectly to chloroplast and 
mitochodrial function with 80-90% accuracy.  Students should be able to explain 
the gain of a phosphate and the loss of a phosphate with the same degree of 
accuracy.  This will be supplemented by a Timer-Board Activity.  What does the 
Timer-Board Activity consist of?  The students will be asked individual terms 
and vocabulary related to the activity which we have just completed. 

     Each participant will be given at least 60 seconds to define a particular 
term or answer a particular question.  Each student will be given (5) points for 
every correct response up to a maximum of (50 points) for an "A" on the Timer-
Board Activity.  Total points will be written on a pre-printed scoring sheet 
beside the names of each of the students (our scoring sheet is our scoring 
board).  The scoring sheet is blocked off so that a number (5) in red ink can be 
written in every block depending on how the student scores. There  is a residual 
2 1/2 points for answers that are not wrong but simply inaccurate.