Photosynthesis key

PART A - CARBON DIOXIDE AS A FACTOR IN PHOTOSYNTHESIS p. 71
Hypothesis: If Cabomba leaves are placed in light, then CO₂ (carbonic acid) should be used up during photosynthesis, turning the solution more basic (red).

Table 1 - The Use of Carbon Dioxide and Photosynthesis

Tube # Tube
Contents Location Color at Start Color at End CO₂ Used?
+ or -

1 ~10cm Cabomba dark yellow yellow -

2 ~10cm Cabomba light yellow red + bubbles? ++

4 ~10cm Cabomba light (green filter) yellow yellow? -

3 ~10cm Cabomba light (red filter) yellow orange + bubbles? +

Tube #	Tube Contents	Location	Color at Start	Color at End	CO₂ Used? + or -
1	~10cm Cabomba	dark	yellow	yellow	-
2	~10cm Cabomba	light	yellow	red + bubbles?	++
4	~10cm Cabomba	light (green filter)	yellow	yellow?	-
3	~10cm Cabomba	light (red filter)	yellow	orange + bubbles?	+

The green filter allows only green light to pass to the Cabomba, but the green leaves do not absorb green light, so this filter acts as if it blocks all light.

Questions:
1. Explain why Phenol red is a good indicator of photosynthesis?
  Phenol red turns red in basic (and neutral) solutions: photosynthesis should remove CO₂ (carbonic acid) and increase pH (red).
2. What product is made by the plant during the light independent reactions?
  Sugar (glucose) is made in light independent reactions ("synthesis" reactions or Calvin cycle).
3. Is CO₂ used in the light dependent or the light independent reactions?
  CO₂ takes part in the light independent reactions ("synthesis" reactions or Calvin cycle), serving as a source of carbon.
4. Was your hypothesis regarding CO₂ supported by your data? p. 72
  Hopefully! Hypothesis: If photosynthesis occurs (with light), then pH will increase as CO₂ is removed, and Phenol Red will turn from yellow to red.
5. Which tubes were your controls in this experiment? Why were those tubes necessary?
  The tubes in the dark served as controls. Need controls to compare with experimental group exposed to light.
6. Can the light dependent reactions continue to produce NADPH and ATP if there is no CO₂?
  No. The light dependent reactions ("photo" reactions) produce ATP that must be used by the Calvin cycle to recycle ATP back to ADP.
7. Can the light independent reactions continue to produce sugars without light?
  No, need ATP and NADPH from "photo" reactions for energy.
PART B - LIGHT INTENSITY AS A FACTOR IN PHOTOSYNTHESIS
SKIP
PART C - COLOR OF LIGHT AS A FACTOR IN PHOTOSYNTHESIS p. 74
OPTIONAL
1. Does the rate of photosynthesis depend on the color of available light?
  It should.
2. Which color of light resulted in the highest rate of oxygen production?
  White color (no filter) should be most productive, since white is the presence of all colors. Green filter should be least productive, since chlorophyll does NOT absorb the green colors transmitted through the filter.