ANTIOXIDANT DEFENCE

So why are we not going rancid? (Hvorfor harskner vi ikke?)

We have evolved a complex, integrated antioxidant defence system.

Some antioxidants are synthesised, and some are needed from food.

ANTIOXIDANT DEFINITION:

• An antioxidant is any substance that, in low concentration compared to the oxidisable substrate, significantly delays oxidation of the substrate
• An antioxidant is a substance that reduces oxidative stress

Antioxidant Mechanisms

• Decreasing O₂ concentration
• Preventing initiation of damage by scavenging free radicals
• Binding transition metals (such as iron) to stop Fenton reactions
• Breaking ROO• chain reactions

Binding transition metals

Caeruloplasmin, ferritin, transferrin and lactoferrin all stop Fenton reactions.

Figure
Overview of antioxidant cycle reactions
Vitamins C and E work in tandem, even though they have different solubility.

Summary

• Life is a battle to avoid going rancid
• ROS-mediated oxidation of biomolecules is implicated in many diseases
• A sophisticated antioxidant defence system minimises oxidation
• Some antioxidants are required from the diet