Cellular Energetics
In photosynthesis, energy enters as a form of light which will then be converted into chemical energy, and carbon dioxide and water are used to store the energy in the form of carbohydrates. The carbohydrate is then taken apart in respiration and the chemical energy is transferred to a different compound called ATP (provides the organelles to do work). In chemosynthesis, energy enters the system in the form of inorganic compounds which have stored energy. The energy is transferred to the bonds of a carbohydrate, meaning that the remaining reactions are the same as a photosynthetic autotroph. On the other hand, heterotrophs take in biochemical energy produced by other organisms, because they can’t use other energy sources.
Electron Transport Chain
The electron transport chain is the final component of aerobic respiration and is the only part of glucose metabolism that uses atmospheric oxygen. Electron transport is a series of redox reactions that resemble a relay race. Electrons are passed rapidly from one component to the next to the endpoint of the chain, where the electrons reduce molecular oxygen, producing water. This requirement for oxygen in the final stages of the chain can be seen in the overall equation for cellular respiration, which requires both glucose and oxygen.
A complex is a structure consisting of a central atom, molecule, or protein weakly connected to surrounding atoms, molecules, or proteins. The electron transport chain is an aggregation of four of these complexes, together with associated mobile electron carriers. The electron transport chain is present in multiple copies in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes.
Light Reactions of Photosynthesis
Chloroplast in plants use light energy to convert into sugars that can be used for the cell, which is where photosynthesis occurs. The chloroplast contains an electron transport which contains four threshold that the light photons will go through. The four thresholds are Photosystem II, Cytochrome B6F Complex, Photosystem I, and ATP Synthase. Throughout these four thresholds, a light photon will enter into a chlorophyll molecule in Photosystem II and the resonance energy will move around neighboring chlorophyll molecules that surrounds the reaction center which is embedded in Photosystem II. Two electrons will be released from the reaction center and then transported into Plastoquinone QB which will then be transport over to the Cytochrome B6F Complex. The two electrons will then go through Photosystem I and ATP Synthase in order to create ATP from ADP. Hence, the light reactions of photosynthesis is the transferring of electrons from one threshold into another which will then convert light energy into chemical energy.
Calvin Cycle
The Calvin Cycle is divided into three main stages: carbon fixation, reduction, and regeneration. Carbon Fixation is where organisms convert inorganic mater into organic mater. The cycle starts off with CO2, start subscript, 2, end subscript molecule combines with a five-carbon acceptor called ribulose-1,5-bisphosphate (RuBP). This step makes a six-carbon compound that divides into two molecules of a three-carbon compound, 3-phosphoglyceric acid (3-PGA). This reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase, or rubisco. Reduction, the second stage, ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, glyceraldehyde-3-phosphate (G3P). This stage is considered a reduction because NADPH donates electrons to a three-carbon intermediate to make G3P. In the regeneration process of the starting molecule, a few G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor.
References:
http://www2.sluh.org/bioweb/apbio/apclassoutlines/ol_cellular_energetics.htm
https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-calvin-cycle-reactions/a/calvin-cycle
https://www.boundless.com/biology/textbooks/boundless-biology-textbook/cellular-respiration-7/oxidative-phosphorylation-76/electron-transport-chain-362-11588/