Principles Module 28
- Discuss the two major interdependent steps of photosynthesis
- Recognize that photosynthesis is, in many ways, the reverse of respiration
- Describe the first step of how light energy is transformed into chemical energy
- Photosynthesis transforms light energy into chemical energy
- Net reaction: CO2 + H2O + light → (CH2O)n + O2
- Photosynthesis is two interdependent pathways
- light-dependent reactions
- light energy used to produce ATP and NADPH, temporary high-energy molecules
- light-independent reactions
- ATP and NADPH ‘spent’ to reduce carbon, making carbohydrates
- Light energy begins to be transformed into chemical energy when it strikes pigments in the leaf
- pigments absorb light at specific wavelengths based on their structure
- light absorbance results in the rearrangement of electrons on a molecule
- molecular excitation is when the electrons are rearranged, conserving the energy of light
- photo-oxidation is when an electron is lost off a molecule, travels to a nearby molecule called an electron acceptor
Questions for Practice
- In what ways are the light-dependent reactions dependent upon the carbon reactions?
- What would happen if the plant were unable to take in CO2 for some reason?
- What is the role of NADPH in photosynthesis?