Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 21 : Pentose Phosphate Pathway or HMP Shunt

Degradation of starch or hydrolysis

The starch granule is the only structure that is synthesized as a highly crystalline matter in the cell. It is synthesized in the plant in a manner to allow dense packing of easily accessible energy combined with highly regulated degradation. One of the main mechanisms to generate such a degradable starch granule is its phosphorylation. The phosphate groups are bound as monoesters at the C-6 and the C-3 position of the glucose units. The remarkable effect of these phosphate groups is that they somehow signal degradation of the starch granule when needed. This mechanism is discovered quite recently. Starch is glucose-polymer consisting of an alpha-1,4 glucosidic-linked backbone giving linear amylose and an alpha-1,4 and alpha-1,6 mixed glucosidic molecule constituting branched amylopectin.