Seed science Starch_Breakdown_in_Cereals.pptx

Starch breakdown

1. Breakdown of Starch in Cereals During Germination Starch hydrolysis and sugar mobilization

2. 1. Starch Composition and Initial Breakdown Starch granules are made of: - Amylose (linear) - Amylopectin (branched) Enzyme α-amylase acts on both: - Amylose → Glucose + Maltose - Amylopectin → Maltose + Limit dextrin + Glucose

3. 2. Further Breakdown of Amylopectin Debranching enzyme acts on limit dextrins and glucose oligomers. α-glucosidase (maltase) breaks down: - Maltose → 2 Glucose - Glucose oligomers → Glucose

4. 3. Glucose Utilization Pathways a. Glucose → Glucose-1-Phosphate → UDP-Glucose b. UDP-Glucose + Fructose → Sucrose + UDP

5. 4. Key Enzymes Involved • α-Amylase – breaks down starch • Debranching enzyme – acts on branched chains • α-Glucosidase – converts maltose to glucose • UDP-Glucose Pyrophosphorylase – forms UDP-Glucose • Sucrose synthetase – synthesizes sucrose

6. 5. Final Products • Glucose – used for energy via respiration • Sucrose – transported to growing regions of the seedling