> [!example] Important Metabolic Pathways > - [[Carbohydrate Metabolism]] > - [[Cellular Respiration]] > - [[Glycolysis & Gluconeogenesis]] > - [[The Citric Acid Cycle]] # Metabolism - Life obeys the laws of thermodynamics - Chemical reactions in cells are organized into pathways - Every reaction of a pathway is catalyzed by an [[Enzymes|enzyme]] or ribozyme It’s crucial for the body to maintain a [[Physiology|physiological pH]] (~7.35-7.45) to ensure a balance of acidity and alkalinity. --- **Metabolism** is the total of all chemical reactions in the cell and is divided into two parts: ![[Pasted image 20231024170424.png|300]] 1. *Catabolism* (Break it down) - Fueling - Energy conserving - Provides reducing power 2. *Anabolism* (To build it up) - The synthesis of complex organic molecules (which requires energy) - 12 Carbon Skeletons The slowest enzyme in a pathway limits the entire metabolic pathway and is sometimes referred to as the pacemaker. **ATP Synthase:** The "turbine" of the electron transport chain that allows electrons to flow between the mitochondira's inner layer via [[Diffusion and Osmosis| passive diffusion]]. ## Types of Metabolism ### Heterotrophs vs Autotrophs **Autotrophs** are organisms who use carbon dioxide as their carbon source. They fuel the reactions to fix $CO_2$ via either: - *lithotrophy*: the use of inorganic compounds as energy, or - *phototrophy*: the use of light as energy (Ex: [[Photosynthesis]]) > [!info] **Where Does Our Energy Come From?** > **Physics** is a driving force behind biological energy generation, it isn't the direct product of a chemical reaction although molecules such as ATP can serve as the batteries ## Electron Carriers NADH and NADPH accepts two electrons and one proton ![[Pasted image 20231021095905.png|400]] ## Metabolism Regulations Metabolic channeling influences pathway activity by localizing metabolites and enzymes to specific parts of a cell - One example of this is compartmentation (most common in eukaryotes)