STARCHES

Carbon flow in metabolism

Starch, Surcose, Cell wall

Sugar Phosphates

Most common in cells

Sugar nucleotides

Activated sugars,

• key role in metabolism

Nonreducing end 

end where the anomeric carbon is tied up in a bond 

Reducing end

end of a carbohydrate chain with a free anomeric carbon

Features of starch

• are made of polysaccharides, and they’re stored in granules inside plant cells

• Temporary storage in the chloroplast (assimilatory starch)

• Long-term storage in amyloplasts (reserve starch)

• alpha (1,4) & alpha (1,6) linkages 

The budling blocks of sucrose and starch

triose-phosphate

Where does Starch synthesis happen

In chloroplasts 

Forms of starch synthase

• Granule-bound (enzyme bound to starch granules)

  • makes amylose

• Soluble (free in the stroma)

  • makes amylopectin

Starch degradation enzymes 

• α-amylase

• β-amylase

• glucan-water dikinase & phosphoglucan-water dikinase

• starch phosphorylase

• debranching enzyme 

• glycosidase  

Regulation of starch degradation involves

phosphorylation and thioredoxin- ensures starch lasts overnight

Transitory starch

starch that’s temporarily stored in chloroplasts during the day