Carbon/Oxygen Cycle (Photosynthesis)

Building Leaf

Note: Leaf model will be built ahead of time and reused

Materials

   Leaf:

• poster board (five colors: white, yellow, light blue, dark blue and red) 

• 1 green twin-size blanket

• 1 green twin-size sheet

• 2 sheets (6’ square) of clear heavy-weight vinyl (shower curtain liners work well) 

• 3 yards 1/4-inch plastic tubing permanent 

• green marker 

• craft glue 

Plant Cell 

• 2 square yards green cotton fabric,

• 1 square yard gray felt

• 1 felt square (23 × 30 cm), any color

• 2 square yards clear heavyweight vinyl

• marker 

• craft glue 

Procedure 

   Build leaf: 

• Cut out 30 circles with a diameter of 10 cm of four different colors (white, yellow, light blue, and dark blue) of poster board. 

• Write oxygen on one side of the white circles and O2 on the reverse side

• On the yellow circles write carbon dioxide on one side and CO2 on the other.

• On the light blue circles write glucose on one side and C6H12O6 on the other.

• On the dark blue circles write water on one side and H2O on the other. 

• From red poster board, cut diamond shapes 13.5 cm long to represent energy.

• Write ATP on one side and energy on the other.

• Layer the four fabrics on top of one another as follows: 

               Bottom layer: vinyl

               Second layer: blanket

               Third layer: vinyl 

               Top layer: sheet

• Use the marker to trace a leaf on one of the layers of vinyl. The leaf should be at about 2 m wide from tip to tip.

• Use heavy-duty shears to cut out the leaf shape from the vinyl, then use it as a cutting template for the other layers.

• Before relayering your leaf, use the marker to draw pairs of guard cells on the bottom layer of vinyl to create open and closed stomata about 24 cm long and 14 cm wide. The open stomata should resemble a pair of open lips and the closed stomata should resemble a pair of closed lips. Cover the vinyl with as many stomata as possible. 

• Draw capsule-shaped chloroplasts, each about 26 × 13 cm, on the other layer of vinyl. Again, fill the layer of vinyl with as many chloroplasts as possible. Tip: You can draw the stomata and chloroplasts on a sheet of paper, which can then be placed under the sheets of vinyl and traced.

• Relayer the fabrics and sew them together along their outer edge.

• Cut a window the size of a pillowcase in the center of the sheet to create a gap that students can raise up to view the chloroplasts.

• On the stomata layer of vinyl, create a pore by cutting out the vinyl between the two guard cells that form each open stomata. This opening allows for the exchange of gases.

• Thread plastic tubing between stitches down the center of the leaf between the blanket and stomata layers of the leaf. A hole needs to be cut in the sheet of vinyl to insert the tubing in one end. The tubing only needs to be glued in place at one end. It will extend 60 cm out the other end of the leaf. The tubing runs right down the middle of the leaf and continues out the end. The tubing represents the vein of the leaf. 

   Build plant cell 

• Use a 1.5 × 0.75 m piece of green cotton fabric as the background of the plant cell. I made the plant cell rectangular with rounded edges. 

• Cut capsule-shaped mitochondria out of the gray felt, each approximately 34cm long and 17 cm wide, and glue them to the green fabric background. 

• Cut a large circle out of any color of felt to represent the nucleus and glue it anywhere on the green background. 

• Cut the vinyl to the exact size and shape of the green cotton fabric.

• Use a marker to trace capsule-shaped chloroplasts, each approximately 26cm long and 13 cm wide, along the outer edge of the vinyl. 

• Sew the vinyl to the green felt, but do not create a continuous seal around the edge. Leave gaps in the stitching large enough to insert the circles representing the elements and compounds to model the semipermeability of the cell. Molecules of glucose, oxygen, water, and carbon dioxide move through these openings.

   Procedure for leaf/plant cell model created above

• Introduction: Photosynthesisis the chemical process by which green plants convert sunlight into sugar. A wave of light energy is converted into chemical potential energy, which the plant then stores in the molecular bonds of sugar molecules. Sunlight + 6H2O + 6CO2 → C6H12O6 + 6O2 Respiration — which releases stored energy for use — occurs in the mitochondria of each cell with CO2 being released as a waste product.

• Students examine the vein (plastic tubing) that runs down the center of the leaf, delivering water to the leaf from the roots of the plant. The water (more poster board circles) inside the leaf is released from the vein through osmosis. This initial examination demonstrates that the reactants of photosynthesis—water, chlorophyll, and carbon dioxide—are available within the leaf. 

• Turn the leaf back over to see where the process of photosynthesis takes place. Sunlight shining on the leaf triggers a chemical reaction among the carbon dioxide, water, and chlorophyll. The carbon dioxide (which enters the leaf through the stomata) and water (which enters through the vein) are represented by poster board circles within the model, but the chlorophyll is just assumed to be present within the chloroplast. 

• The sun shines through the leaf hitting the chloroplast. The interaction of the sunlight, chlorophyll, water, and carbon dioxide produces oxygen (O2) and glucose (C6H12O6), which are represented by poster board circles. The oxygen passes out of the leaf through the stomata and the glucose is stored within the leaf. 

• Have students explain the process in their own words while manipulating the parts of the model. 

• The students will use the circles representing carbon dioxide, oxygen, water, energy, and glucose to show photosynthesis and respiration. The students will take the giant plant cell, put glucose and oxygen circles on one side of mitochondria, and show carbon dioxide, water, and energy on the other side. Reverse process to discuss respiration.

Conclusion

• Look at the carbon cycle. How do plant fit into that cycle?

• What do you think would happen to the carbon cycle if the number of plant in the world were to be drastically reduces?

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