> See also: > - Reference # Photosynthesis Photosynthesis is a biological process Organisms capable of performing photosynthesis are known as **autotrophs**, specifically **photoautotrophs** Plants perform both cellular respiration and photosynthesis, because of this they are able to survive in isolated environments (as long as there is light and carbon dioxide) Like it's counterpart, [[Metabolism]], photosynthesis is known as a [[Reduction Oxidation Reactions|redox reaction]]. $ 6CO_2 + 6H_2O + \text{Light Energy} \rightarrow C_6H_{12}O_6 + 6O_2$ - reactants: > [!info] Responding to Light > > **Phototropism** is the ability for plants to shift/lean in the direction of light to improve their ability to photosynthesize > ### Chlorophyll Chlorophyll is green because it is absorbing all other [[Electromagnetic Energy|wavelengths]] of light and only reflects the green light that we see. - Plants would actually perform photosynthesis the worst under green light because of this. Fall colors occur because certain pigments can easily break down at lower temperatures. - This is useful as the light in the atmosphere can change through seasons of the year ### Basic Photosynthetic Structures - **Stroma:** - **Stomata:** - **Thylakoid:** Contain chlorophyll and is where photosynthesis occurs. - **Grana Stacks:** Stacks of thylakoids ### Stages of Photosynthesis ![[Pasted image 20220802190109.png|400]] There are two major parts of photosynthesis: 1. **Light-Dependent Reactions** *(photo-)* 2. **The Calvin Cycle** *(-synthesis)* | Stage | Overview | Location | | --- | --- | --- | | Light-Dependent Reactions | | | --- ##### Light-Dependent Reactions - Very similar to the electron transport chain in cellular respiration - Splits $H_2O$ - Releases $O_2$ - $NAD^+ \text{full} \rightarrow NADH$ - **Phosphorylation** - $ADP \rightarrow ATP$ ATP is generated by chemiosmsis. An ATP synthase is embedded into the thylakoid membranes The electrons exit through the stroma (interior of chloroplasts). In the thylakoid membrane, photosystem I occurs after photosystem II despite what the name implies. The names are based on the order that they were discovered. - Photosystem I: - Photosystem II: --- ##### The Calvin Cycle The calvin cycle is the light-independent stage of photosynthesis Occurs in the stroma of the chloroplast - endergonic Rubisco is arguably the most important enzyme as it can convert inorganic molecules to organic molecules RuBP is put through carboxylase A 6 carbon molecule is immediately produced There are six steps: 1. Carbon fixation 2. Reduction The end result of the calvin cycle are: - 3 carbon compound (PGAL & G3P)