8.1.pdf

Metabolism: Describes all chemical reactions in a cell. Metabolic pathways: Series of connected chemical reactions that build or break down molecules. Exergonic reactions: Happen on their own and release energy. Endergonic reactions: Need energy to happen. Anabolism: Endergonic pathway...

Metabolism: Describes all chemical reactions in a cell. Metabolic pathways: Series of connected chemical reactions that build or break down molecules. Exergonic reactions: Happen on their own and release energy. Endergonic reactions: Need energy to happen. Anabolism: Endergonic pathways that use energy to build complex molecules from simple ones. Catabolism: Exergonic pathways that break down complex molecules into simpler ones, releasing stored energy. Energy from catabolism is used to fuel anabolism, so cells constantly balance both processes. Here’s a simplified version with key information in bullet points: Organisms are classified based on: ○ Carbon source for metabolism ○ Energy source Carbon Source: Autotrophs: ○ Use inorganic carbon dioxide (CO2) to make organic carbon compounds. ○ Examples: Plants, cyanobacteria. Heterotrophs: ○ Use complex organic carbon compounds for nutrients. ○ Examples: Humans, Escherichia coli. Energy Source: Phototrophs: ○ Get energy from light. Chemotrophs: ○ Get energy from breaking chemical bonds. ○ Two types: Organotrophs: Use organic compounds for energy (e.g., humans, fungi). Lithotrophs: Use inorganic compounds for energy (e.g., hydrogen sulfide, reduced iron). This is unique to microbes. Combined Classification: Most organisms are chemoheterotrophs: ○ Use organic molecules for both energy and carbon sources. Oxidation and Reduction in Metabolism: Electron transfer between molecules is key to storing and using energy in cells. Energy is transferred in small amounts via electrons, preventing damage to the cell. Oxidation reactions remove electrons from molecules, leaving them oxidized. Reduction reactions add electrons to molecules, leaving them reduced. Redox reactions: Oxidation and reduction always happen together. Energy Carriers: NAD+, NADP+, FAD, and ATP: Energy from breaking down nutrients is stored in electron carriers or ATP. Main electron carriers are from the B vitamin group and include: ○ NAD+/NADH (oxidized/reduced forms) ○ NADP+/NADPH (involved in anabolic reactions and photosynthesis) ○ FAD/FADH2 (used in breaking down sugars) These carriers have reducing power because they donate electrons in chemical reactions. ATP (Adenosine Triphosphate): ATP is the cell’s "energy currency" and stores energy for later use. AMP (Adenosine Monophosphate) is the basic building block of ATP. ○ Adding phosphate groups creates ADP (two phosphate groups) or ATP (three phosphate groups). Breaking the bonds between phosphate groups in ATP releases energy to power cell processes. Phosphorylation: Adding phosphate groups requires energy, while removing them releases energy. Important Information in Bullet Points: Catalysts speed up chemical reactions and are reusable. Enzymes are protein catalysts in cells, controlling cellular metabolism. Activation energy is the energy needed to start a chemical reaction. Enzymes lower activation energy by binding to substrates at the active site. Enzyme specificity: Enzymes fit with substrates like a "jigsaw puzzle." Induced fit: Enzyme changes shape slightly to fit the substrate better. Environmental influences: Temperature, pH, and substrate concentration affect enzyme activity. ○ High temperatures or extreme pH can denature enzymes, stopping their function. Substrate concentration: Enzyme activity increases with more substrate until saturation. Cofactors (inorganic) and coenzymes (organic) help enzymes work. ○ Example of cofactors: iron (Fe²⁺), magnesium (Mg²⁺), and zinc (Zn²⁺).  ○ Example of coenzymes: vitamins, NADH, and ATP. Enzymes needing helpers but without them are called apoenzymes (inactive). Enzymes with the necessary helpers are called holoenzymes (active). Enzyme regulation: Enzymes can be controlled to either increase or decrease their activity. Competitive inhibitors: Resemble the substrate and compete for the enzyme’s active site. They block the substrate from binding. Effective when the inhibitor concentration is about equal to the substrate concentration. Example: Sulfa drugs treat bacterial infections by blocking enzymes in the bacterial folic acid pathway, preventing bacteria from growing. Humans are not affected since we get folic acid from our diet. Noncompetitive (allosteric) inhibitors: Bind to a different site on the enzyme (not the active site). Cause a change in the enzyme’s shape, reducing its ability to bind to the substrate. Only one inhibitor per enzyme is needed, so lower concentrations are required compared to substrates. Allosteric activators: Bind to a site away from the active site and increase the enzyme’s ability to bind to its substrate. Feedback inhibition: Cells use products from their own reactions to regulate enzyme activity. When enough product is made, the cell slows down production during anabolic (building) or catabolic (breaking down) processes.