There are three main types of food molecules, proteins, carbohydrates, and fats. These can each be found in different foods, and are precessed lightly differently. While you digest your food the food molecules are broken down into their component parts. Then in cellular respiration, those parts are each processed and the energy inside them is used to produce ATP. Nucleotides are also technically food molecules, and any DNA or RNA you eat will be broken down into its constituent parts.
Carbohydrates are either small carbon chains or chains of smaller carbohydrates. There are simple carbohydrates, which are sugars, or small carbon chains, and complex carbohydrates, like starch, which are long chains of simple carbohydrates.
Some example of simple carbohydrates are glucose, a 6-carbon chain, fructose, another 6-carbon chain, galactose, another 6-carbon chain, deoxyribose, a 5-carbon chain, sucrose, a combination of glucose and fructose, and lactose, a combination of glucose and galactose.
Some example of complex carbohydrates are starch, a glucose chain, cellulose, another glucose chain, and glycogen, a glucose structure.
Fats are hydrocarbons, meaning they are mostly composed of hydrogen and carbon. There is a base called glycerol, to which 3 fatty acids attach, forming a fat molecule.
Proteins are long chains of amino acids. Proteins get folded up in a particular way based on the order the amino acids are in. There are 20 total amino acids, and they can be arranged in many many different ways. Proteins are like the workers of cells, they do everything.
Cellular respiration is the process that turns food into usable energy for cells in the body. All food molecules ca go through cellular respiration, but we will be focusing on glucose. Other molecules will have a slightly different chain of reactions than glucose but the main idea is the same. Cellular respiration requires oxygen and and produces carbon dioxide and water as an output.
In glycolysis, glucose goes through a series of reactions that transforms it into pyruvates. The process uses 2 ATP molecules, but yields 4, so there is a net gain of 2 ATP molecules. The process also yields a few ions, which will be used in the electron transport chain.
In the citric acid cycle, also known as the Krebs cycle, the pyruvate bonds with citric acid and then goes through a chain of reactions yielding a lot of ions, which will be used in the electron transport chain. The citric acid cycle takes place in the matrix.
The ions are used by a protein to push protons from the matrix to the intermembrane space of the mitochondria. Then a protein called ATP synthase preforms facilitated diffusion and lets the protons go back into the matrix, where there is a lower concentration of protons. As the protons pass through ATP synthase, it uses that energy to add a phosphate group on the end of ADP molecules to create ATP. Much more than the mere two that ere made during glycolysis.
Photosynthesis is the process that plants use to produce food from light energy. They use the energy from light to rearrange the atoms in carbon dioxide and water to form glucose, a carbohhydrate, with a byproduct of oxygen. Photosynthesis happens in the chloroplasts, which are organelles in a plant cell.
The light dependent reactions take place on the membrane of the thylakoid. When sunlight hits the chlorophyl in the thylakoid, it excites the electrons inside the chlorophyl. Then multiple reactions take place that put this energy into ATP and some other temporary energy holding molecules.
The light independent reactions, which are mostly comprised of just the Calvin cycle, are a series of reactions that use the energy from the light dependent reactions and a little bit of ATP to, in essance, convert carbon dioxide into a form of glucose. The light independent reactions happen inside of the thylakoid.