3.5 Vitamins and Cofactors

Module I – Molecular Foundations of Plant Biochemistry

1. Introduction

Vitamins and cofactors are small organic molecules required for proper enzymatic function. Although present in low concentrations, they are essential for metabolic regulation and plant health.

Vitamins and cofactors enable enzymes to function efficiently in plant biochemical systems.

2. Vitamins in Plant Systems

Many plant vitamins function as antioxidants or enzyme cofactors.

Vitamin	Biochemical Role	Horticultural Importance
Vitamin C (Ascorbic acid)	Antioxidant, redox regulation	Stress tolerance, nutritional value
Vitamin E (Tocopherol)	Membrane protection	Protection against oxidative damage
Vitamin B complex	Coenzyme formation	Metabolic efficiency

Plants synthesize most vitamins internally, unlike humans.

3. Cofactors and Coenzymes

Cofactors are non-protein molecules required for enzyme activity.

Metal ions (Mg²⁺, Fe²⁺, Zn²⁺)
Organic molecules (NAD⁺, NADP⁺, FAD, CoA)

Without cofactors, enzymes cannot catalyze metabolic reactions.

Cofactor	Function	Relevance
NADH / NADPH	Electron transfer	Energy metabolism, biosynthesis
ATP	Energy carrier	Metabolic activation
Mg²⁺	Enzyme stabilization	Photosynthesis and metabolism

4. Role in Stress and Quality Formation

Antioxidant vitamins protect against oxidative stress.
Cofactors regulate photosynthesis and respiration.
Vitamin content influences nutritional quality of fruits and vegetables.
Redox molecules maintain metabolic balance.

Redox balance and antioxidant capacity are central to plant stress resilience and postharvest stability.

5. Applied Interpretation

Vitamin C content influences fruit market value.
Micronutrient deficiencies disrupt cofactor availability.
Stress conditions alter redox cofactor balance.
Postharvest deterioration is linked to oxidative imbalance.

Understanding vitamins and cofactors strengthens the bridge between molecular biochemistry and crop quality management.