BackCellular Respiration and Fermentation (Chapter 9) – Study Notes
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Cellular Respiration and Fermentation
Overview
Cellular respiration and fermentation are essential metabolic processes that allow cells to extract energy from organic molecules. This energy is primarily stored in the form of ATP (adenosine triphosphate), which powers most cellular work. These processes are fundamental to the survival of both plant and animal cells.
Cellular respiration is the process by which cells break down organic molecules, such as glucose, to generate ATP.
Fermentation is an alternative pathway that allows ATP production in the absence of oxygen.
Both processes are linked to the overall flow of energy in ecosystems, connecting photosynthesis and cellular metabolism.
Catabolic Pathways and Energy Yield
Catabolic Pathways: Oxidizing Organic Fuels
Catabolic pathways involve the breakdown of complex molecules into simpler ones, releasing energy that can be used to produce ATP.
Exergonic reactions are those that release energy during the breakdown of organic molecules.
Aerobic respiration is a catabolic process that consumes organic molecules and oxygen (O2), yielding ATP.
Fermentation is a partial degradation of sugars that occurs without the use of oxygen.
Key Definitions:
Aerobic respiration: A process that requires oxygen to produce ATP by breaking down glucose and other organic fuels.
Fermentation: An anaerobic process (does not require oxygen) that allows cells to generate ATP by substrate-level phosphorylation.
Energy Flow in Cells
Cells obtain energy from food molecules through a series of metabolic pathways. The energy stored in food is ultimately converted into ATP, which is used to drive most cellular processes.
Photosynthesis in plants captures light energy to produce organic molecules and oxygen.
Cellular respiration in mitochondria breaks down these organic molecules, generating ATP and releasing carbon dioxide and water.
ATP produced powers cellular work, and some energy is lost as heat.
Summary Table: Comparison of Aerobic Respiration and Fermentation
Process | Oxygen Required? | ATP Yield (per glucose) | End Products |
|---|---|---|---|
Aerobic Respiration | Yes | ~32 | CO2, H2O |
Fermentation | No | 2 | Lactic acid or ethanol + CO2 |
Key Equations
General equation for aerobic cellular respiration:
Photosynthesis (reverse process):
Example: Energy Flow in Ecosystems
Plants use sunlight to convert CO2 and H2O into glucose and O2 via photosynthesis.
Animals (and plants) use cellular respiration to break down glucose, generating ATP for cellular work.
Heat is released as a byproduct at each step, contributing to the energy flow in ecosystems.
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