Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 16 : Metabolic Pathways

Introduction to Metabolism

Metabolism - sum total of all chemical reactions in living cells

Catabolic reactions - degrade macromolecules and other molecules to release energy

Anabolic reactions - used to synthesize macromolecules for cell growth, repair, and reproduction

Metabolism can be divided into 4 groups: carbohydrates, lipids, amino acids, nucleotides.

1. within each group are a set of pathways
2. arbitrarily set start and end points for ease of learning and reference
3. pathways can take different forms:


• Linear - product of one reaction is substrate for another

e.g. glycolysis

• Cyclic - regeneration of intermediates

e.g. Krebs cycle

• Spiral - same set of enzymes are used repeatedly

e.g. fatty acid synthesis, ?-oxidation

4. each pathway may have branch points for metabolites to enter or leave