Cellular Energy

• Thermodynamics


  The study of energy transfers that occur in molecules or collections of molecules
• System


  Item or collection of items being studied in thermodynamics
• Surroundings


  Everything not included in the defined system in thermodynamics
• Universe


  The system and the surroundings combined in thermodynamics
• Open system


  System which can exchange both energy and matter with its surroundings
• Closed system


  System which can only exchange energy, not matter, with its surroundings
• Isolated system


  System which can exchange neither matter nor electricity with its surroundings
• Laws of thermodynamics


  Physical rules of energy transfer
• First law of thermodynamics


  Energy cannot be created nor destroyed, but can only be transferred from one object to another or change form
• No energy transfer is 100% efficient, because some is lost as heat
• Entropy


  The degree of randomness of disorder of a system
• Heat increases entropy, because fast moving molecules takes away from the order until we are in one bast moving molecule soup. When it is produced as useless energy in an energy transfer, it starts doing its thing to mess everything up
• Second law of thermodynamics


  All energy that escapes as useless heat will go towards increasing the entropy of the universe, and so every chemical reaction in us goes towards that
• Even though systems which locally decrease entropy exist, they need energy to do so, and a good part of that energy ends up being either lost as heat or gotten by making complex molecules more simple
• ATP


  Main "energy currency" of cells which helps "pay for" energetically unfavorable cell activities that are necessary for its survival
• ATP


  RNA nucleotide that bears 3 phosphate chains labelled alpha, beta, and gamma, from closest to furthest from the ribose (which is attached to the nitrogenous base adenine
• Phosphoanhydride bonds


  High energy bonds between the phosphate groups of ATP which lead to them very much wanting to get away from each other, which makes ATP super reactive
• deltaG for the hydrolysis of ATP in a living cell is -14 kcal / mol, which is crazy amounts of free energy being released
• Reaction coupling


  When an exergonic reaction like ATP hydrolysis is directly paired with an endergonic reaction so that it can have enough energy to happen
• Shared intermediate


  Often seen in reaction coupling, when a product of one reaction is the catalyst for the other one to start
• So long as the overall deltaG is negative, any coupled reaction can occur
• Many reactions in the cell use phosphorylated molecules as shared intermediates, so the rest of the reaction knows it has enough energy to keep happening
• Metabolism


  The collective term for all the chemical reactions that happen in a cell
• Cellular respiration


  The process by which cells get energy by breaking down glucose, then storing it in ATP until we need it, when ATP will phosphorylate something and release it back
• Photosynthesis


  Using the energy from sunlight to convert CO2 into glucose. Some of it is used by the plant, and some is used as a food source. Either way, it gets metabolized with ATP
• Metabolic pathway


  Series of connected metabolic reactions that feed off of one another, taking starting molecules, and, though a bunch of intermediates, converts them into products
• Anabolic pathway


  Photosynthesis, metabolism that "builds up" sugars from smaller molecules, typically need energy input
• Catabolic pathway


  Cellular respiration, metabolism that "breaks down" sugars into smaller molecules, lead to energy release