My AP Biology Thoughts  Unit 3 Cellular Energetics

Welcome to My AP Biology Thoughts podcast, my name is Alex Jing and I am your host for episode 68 called Unit 3 Cellular Energetics: Metabolic Pathways & Coupled Reactions in Living Organisms . Today we will be discussing the purpose of metabolic pathways and coupled reactions in living organisms

Segment 1: Introduction to Metabolic Pathways & Coupled Reactions in Living Organisms 

• Metabolism encompasses all reactions that happen within cells
• Series of reactions are organized into metabolic pathways
• These reactions are catalyzed by enzymes, and are either
• Catabolic, which breaks down molecules through hydrolysis, or
• Anabolic, which builds molecules using dehydration synthesis
• Coupled reactions are reactions that are paired together, where one reaction usually releases energy and the other reaction requires energy
• Catabolic reactions are coupled with anabolic reactions so that the energy released by the catabolic reaction is used for the anabolic reaction

Segment 2: More About Metabolic Pathways & Coupled Reactions in Living Organisms 

•  An example of a metabolic pathway is the calvin cycle, which sends pyruvates into a series of reactions to product NADH and FADH, both of which are used to produce ATP. 
• This is done by continuously reducing the pyruvate to provide electrons for NAD+ and FAD+ to reduce to NADH and FADH
• This allows the body to continuously break down pyruvates in a cyclic fashion to produce NADH and FADH to produce ATP.
• An example of coupled reactions in the body is how cells use ATP. Many processes like active ion transport, muscle contraction, and chemical synthesis, are not spontaneous. The body uses ATP to provide the energy for these reactions to proceed by coupling the reactions with the decomposition ATP, using the energy released to fuel the reaction.

Segment 3: Connection to the Course

•  Metabolic pathways and coupled reactions are extremely important to biology. Metabolic pathways allow organisms to manipulate molecules that they consumed into molecules that the body can regularly use
• Coupled reactions allow the body to transfer the energy used in an exergonic reaction to power a reaction that uses the energy released. 

 

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