Photosynthesis

Created March 2020, Offline version here
Video by Mr. J, also on his Youtube Channel.

    Photosynthesis is the opposite process of cellular respiration. It involves the use light and ATP. It is important to realize that the ATP used in photosynthesis used elsewhere in the cell.
    are the types of organisms that conduct photosynthesis. Most of these are , such as plants, but some bacteria can also do photosynthesis. In eukaryotes, the is the cell organelle that is the site of photosynthesis. Within the organelle, the grana which are stacks of , are the site of photosynthesis chemical reactions. Photosynthesis involves chemical reactions known as reactions, where the number of electrons on molecules changes. The process of splits water and is responsible for the oxygen given off by plants undergoing photosynthesis that we can breathe. The end result, after hydrolysis, the light reactions, and the Calvin Cycle is that the plant generates a molecule of .
    Light travels in energy “packets” called photons. These photos arrive and are captured by the plant’s pigments in the thylakoid stacks (grana). These photos excite electrons beginning the process of photosynthesis. Thylakoids are stacks to give the plant surface area for light photons to strike and more efficiently perform this step. Once the light hits the pigment and excites the electron it enters a photosystem, which is similar to the electron transport chain in cellular respiration. The energy of this electron allows the cell to pump H+ the thylakoid. The efficiency of photosynthesis depends on the of light and the pigment present. These pigments are what absorb photons of light and begin photosynthesis. Plant cells contain many different pigments. One such secondary pigment type are , which are yellows and red. These do not get broken down in the fall time as plants prepare for winter and therefore cause what we see as fall leaf color changes. Photosynthesis involves two different systems. actually comes first and is where the photons captured by the pigments extract the electrons from the water molecules. In Photosystem II, hydrolysis happens. For every 2 water molecules split, we generate oxygen and electrons (e-). These electrons are eventually donated back to the pigment molecule and photosystem I. After photosystem II, electrons go to photosystem I where they are used to reduce a molecule and create .The overall process involves light exciting pigment molecules which go through photosystem II. Photosystem II then gives electrons to Photosystem I which generates NADPH. This is known as non-cyclic electron flow.