1. CenUSA Bioenergy High School Curriculum Lesson 3
Photosynthesis
CenUSA Bioenergy High School Curriculum
Lesson 3

2. Introduction to Photosynthesis
Physico-chemical process by which plants, algae and photosynthetic bacteria use light energy to drive the synthesis of organic compounds.
Results in the release of oxygen and the removal of carbon dioxide from the atmosphere.
Other types of bacteria use light energy to create organic compounds but do not produce oxygen.
Provides the energy and reduced carbon required for the survival of virtually all life on our planet, as well as the oxygen necessary for the survival of certain organisms.
Performance of photosynthetic organisms depends on the earth's atmosphere and climate.
When you breathe, your body uses oxygen (O) and gives off carbon dioxide (CO2).

4. Calvin Cycle
Phase I Carbon Fixation: CO2 is incorporated into a five- carbon sugar named ribulose bisphosphate (RuBP). The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It is the most abundant protein in chloroplasts.
Phase II Reduction: ATP and NADPH2 from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars.
Phase III Regeneration: More ATP is used to convert some of the glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO2, completing the cycle.
The light reactions sustain the Calvin cycle by regenerating the ATP and NADPH2.

6. Respiration
Respiration – The process of metabolizing or burning sugars to yield energy for growth, reproduction, and other life processes.
Plants and animals convert the sugars (photosynthates) back into energy for growth and other life processes.
Chemical equation for respiration shows that the photosynthates are combined with oxygen releasing energy, carbon dioxide, and water.

7. Transpiration
Transpiration – The loss of water vapor through the stomata of leaves.
Movement of minerals up from the root (in the xylem) and sugars (products of photosynthesis) throughout the plant (in the phloem). Water serves as both the solvent and the avenue of transport.
Cooling – 80% of the cooling effect of a shade tree is from the evaporative cooling effects of transpiration.
Turgor pressure – Water maintains the turgor pressure in cells much like air inflates a balloon, giving the non-woody plant parts form.
Can remain stiff and upright; gain a competitive advantage when it comes to light.
Important for the functioning of the guard cells, which surround the stomata and regulate water loss and carbon dioxide uptake.
Force that pushes roots through the soil.