Unit C

Module 5 ~Lesson 1

 Metabolic Pathways

Metabolic pathways are interconnected and involve many steps. Plants and animals rely on metabolic pathways to store and provide energy. These pathways can be summarized by the word metabolism.

Photosynthesis and cellular respiration are two important pathways. They can be represented by the following two chemical equations:

6 CO ₂ (g) + 6 H ₂ O(l) + energy → C ₆ H ₁₂ O ₆ (s) + O ₂ (g)

C ₆ H ₁₂ O ₆ (s) + O ₂ (g) → 6 CO ₂ (g) + 6 H ₂ O(l) + energy

The important thing to keep in mind is that these are summary statements. Both processes are a series of reactions that use initial reactants to produce final products. On paper, the second equation looks like the reverse reaction to the first one, but as you work through this unit, you will see that there are many differences between the two processes.

The series of reactions become a metabolic pathway. Metabolic pathways transfer energy and cycle matter in living organisms. 

Catabolic pathways break larger molecules down into smaller ones. Cellular respiration is a catabolic reaction. Energy is released in this process.

Anabolic pathways form larger molecules from smaller ones. Photosynthesis is an anabolic reaction. Energy is required for this process.

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