The electromagnetic spectrum includes the visible light portion in addition to gamma rays, X-rays, ultraviolet radiation, infrared radiation, microwaves, and radio waves.
Chloroplasts are organelles that contain the other structures or substances. Inside the inner membrane of the chloroplast, the stroma is a fluid-filled space that surrounds grana, which are stacks of thylakoids.
In the first stage of photosynthesis (light reactions), light energy is captured by pigments and converted to the chemical energy of ATP and NADPH. In the second stage of photosynthesis (carbon reactions), the energy of ATP and the electrons in NADPH are used to make glucose from CO2.
produces ATP: light energy transferred to reaction center, two electrons are ejected, water is split to replace electrons, O2 is a by-product, ejected electrons move down transport chain, H+ is pumped into thylakoid, H+ leaves through ATP synthase, ATP is produced
produces NADPH: electrons reach photosystem I, energy from light again ejects electrons into a transport chain, electrons reduce NADP+ to NADPH
Describe the events that occur after light strikes photosystem II, ending with the production of ATP
In photosystem II, light strikes a photosynthetic pigment; energy is absorbed; energy bounces to the chlorophyll molecule in the reaction center, which releases two energized electrons; the electrons are replaced by two electrons stripped from a water molecule, forming oxygen gas (O2) and two hydrogen ions (H+); as the energized electrons move along the proteins of the electron transport chain of photosystem II, hydrogen ions accumulate in the space within the thylakoid, forming a reservoir of potential energy; as ATP synthase moves hydrogen ions back to the stroma, the released energy bonds a phosphate group onto ADP, forming ATP.
Electrons pass from photosystem II to photosystem I in an electron transport chain. Light strikes antenna pigments in photosystem I; these pigments transfer the energy to the reaction center chlorophyll molecule of photosystem I. The reaction center chlorophyll releases two energized electrons, which are replaced by the electrons from photosystem II.
The boosted electrons lost from the reaction center in photosystem II are replaced by electrons stripped from a water molecule.
In photosystem I, energy from sunlight energizes a pair of electrons in the reaction center (replaced by a pair of electrons from photosystem II) and these are passed to molecules of NADP+ to reduce them to NADPH. This molecule carries the electrons (and potential energy) to the carbon reactions of photosynthesis.
CO2 is the source of the carbon atoms that eventually become a glucose molecule. ATP provides the energy and NADPH provides the electrons for the Calvin cycle reactions.
The CAM pathway is like C4 metabolism since it occurs in plants from a hot and dry climate, and a four-carbon compound is used during the fixation of CO2. CAM plants differ from C4 plants as they open their stomata at night and CO2 diffuses into spaces within leaves. Mesophyll cells then store the carbon dioxide in a four-carbon molecule within a vacuole. In the daytime, CAM plants minimize water loss by keeping their stomata closed, but CO2 is released from the vacuoles and enters the Calvin cycle.