Write and interpret the balanced chemical equations for photosynthesis and cellular respiration, and connect them to matter cycling and energy flow studied earlier this year.
Photosynthesis and cellular respiration are both real chemical reactions, and writing them as equations makes the connection to this month's reaction ideas exact. Photosynthesis, happening in chloroplasts, is: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2. In words: six carbon dioxide molecules plus six water molecules, using captured light energy, become one glucose molecule plus six oxygen molecules. Cellular respiration, happening in mitochondria in essentially every living cell, including a plant's own cells, is essentially the reverse: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy, releasing usable energy the cell can actually use.
These two equations are not just abstract formulas -- they are the chemistry underneath two ideas from earlier this year. They are the main engine of the carbon cycle studied in week 11: photosynthesis pulls carbon dioxide out of the air into living matter, and respiration returns it. They are also exactly how the energy pyramid from week 10 gets started and continues: photosynthesis captures the sun's light energy and stores it as chemical energy in glucose, and respiration is how that stored energy is released so it can actually be used by a cell, at every trophic level of that pyramid.
Mastery looks like: They can identify the reactants and products of both equations, verify that each balances by counting atoms, and explain the connection to matter cycling and energy flow.
Common stumbles: Assuming plants only photosynthesize and never respire; treating the two equations as unrelated instead of recognizing them as near-mirror-image reactions.