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Introduction to Metabolism and Bioenergetics
Metabolism: Entire network of enzyme reactions in cells
Two major domains:
Anabolism: Reactions that synthesize molecules or make more complex molecules
Catabolism: Reactions that degrade larger molecules to smaller molecules
Anabolism: Reactions require energy and produce a wide diversity of macromolecules
using a smaller number of simpler molecules. e.g 20 amino acids used to make thousands
Examples of anabolic paths:
Synthesis of glucose from pyruvate
Synthesis of glycogen (polyglucose) from glucose
Synthesis of fatty acids from acetyl CoA
Catabolism: These reactions usually liberate energy and can convert a wide variety of
larger molecules into a smaller variety of small molecules e.g. thousands of proteins →
20 amino acids
Examples of Catabolic Paths:
Glycolysis: Breakdown of glucose 6C to 2 pyruvate 3C
β-oxidation: Breakdown of fatty acids to acetyl CoA
Glycogenolysis: Glycogen to glucose-1 phosphate
Roles of Metabolism:
1. To produce energy by the breakdown of fuels such as glucose and fatty acids
2. To make molecules such as DNA, RNA, lipids, proteins, amino acids, glucose.
3. To make fuel storage molecules such as triglycerides and glycogen
4. To convert one molecule into another eg glucose→FA
Generally energy released during catabolism is used in anabolic pathways or in cellular
work (e.g. muscle contraction)
Pathways: The synthesis or breakdown of a molecule usually relies on a number of
sequential enzyme reactions
The product of one reaction serves as substrate for the next enzyme in line.
A linear pathway: a number of enzyme steps in sequence to achieve a final product.
Glycolysis is an example of a linear pathway
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