Photosynthesis is performed by the Thylakoid and Chloroplast parts.
Photosynthesis is the process of Utilizing Light (Lux) to produce Glucose (And an oxygen byproduct) from CO2. This means that photosynthesis will only be viable in locations with high brightness and CO2 concentration, so make sure your current location can support this process before trying to rely on it. Photosynthesizing parts are also quite heavy, so be prepared for slower movement relative to other species.
Use and Strategy
Photosynthesis is available to both prokaryotes and eukaryotes through Thylakoids and Chloroplasts respectively. Due to the patch-wide presence of light and CO2, photosynthesis can be an incredibly useful means of passive glucose generation that will ensure the player always has a reliable source of energy so long as they correctly balance their rate of glucose production with consumption. Due to being heavier than most other cell parts, cells that specialize in photosynthesize will be slower than many others, and will likely need to rely on physical defenses instead of outrunning predators. It is also important to use parts that perform Respiration in order to make effective use of the resulting glucose you produce from photosynthesis.
This prokaryotic part takes up a single hex of space, but also produces glucose at a relatively slow pace. Possessing around 2 Thylakoids per Metabolosome (At 100% Lux) is a reliable method to make sure you will always produce more glucose than you consume as a prokaryote.
Chloroplasts are the eukaryotic organelle for photosynthesis that take up three hexes of space, making them one of the largest common organelles. They are quite heavy, but produce glucose at a much more rapid pace compared to as many as three Thylakoids. It may be helpful to replace any instances of thylakoids with this part to make effective use of it's higher production rates once available. Utilizing one chloroplast for every couple of mitochondria (At 100% Lux) is a reliable way to ensure that you produce enough glucose to sustain yourself.
Function in Reality
In real life, photosynthesis is one of the most common and well-known cellular processes besides Respiration, and is well known for being utilized by not just almost every plant on earth, but also by a large amount of microbial species and even some motile animals.
The act of photosynthesis is carried out by the utilization of pigments known as chlorophyll which absorbs the photons from sunlight, resulting in a flow of electrons from the chlorophyll, and thus instigating the electron transport chain used to reduce NADP and ADP into NADPH and ATP respectively. The electrons lost by the chlorophyll are restored by taking hydrogen from H2O, producing the O2 byproduct plants are widely known for. The resulting products alongside the addition of CO2 are then converted through a process widely known as the Calvin Cycle into the storage molecule glucose, where it is stored until needed.
Where it Takes Place
In order to properly perform photosynthesis, prokaryotic organisms compartmentalize the process by packing Chlorophyll into membranes known as thylakoids, within which the process of photosynthesis occurs.
Chloroplasts are eukaryotic structures which are actually membranes that contain a large host of thylakoids within themselves, resulting in a more productive and efficient means of photosynthesis. It is theorized that through the process of endosymbiosis, eukaryotic species have been able to integrate entire photosynthetic prokaryotes into their own structure, resulting in the Chloroplasts of today.