Starch green algae

Chloroplasts (29-36) are the sites of photosynthesis and their ribosomes can carry out protein synthesis. Chloroplasts that contain chlorophylls and carotenoids, are disc shaped and 4-6 pm in diameter. These plastids are comprised of a ground substance (stroma) and are traversed by thylakoids (flattened membranous sacs). The thylakoids are stacked as grana. In addition, the chloroplasts of green algae and plants contain starch grains, small lipid oil droplets, and DNA. 

Starch is formed in chloroplasts of moss, fern and green algae.18 Chlorophyceae (green algae) starch is similar to that of higher plants, and several species have been used in studies of starch biosynthesis.19,22,29 In a recent set of studies, Ball et al.22 used Chlamydomonas reinhardtii to study starch biosynthesis. They produced several Chlamydomonas mutants which produce starch with characteristics similar to starches produced by maize endosperm mutants.31-34 The various starch mutations of Chlamydomonas will be discussed in Section 3.7. Other classes of algae which produce starch are Prasinophyceae19,35 and Cryptophyceae.35,36... 

Analyses of the starch biosynthetic system in a number of plants and green algae indicate that an important site of regulation of starch synthesis is at the ADPGlc PPase and that 3PGA and Pi are important regulatory metabolites of that enzyme. 

In green algae and in leaf cells of higher plants, ADP-Glc PPase has been demonstrated to reside in the chloroplast (82). More recently, using plastids isolated from maize and barley endosperm (83-85), the existence of two ADP-Glc PPases, a plastidial form, and a major cytosolic form were found. Subsequently, cytosolic forms of ADP-glucose pyrophosphorylase have been found in wheat (86, 87) and rice (88). Because starch synthesis occurs in plastids, it was proposed that in cereal endosperms, synthesis of ADP-Glc in the cytosol requires the involvement of an ADP-Glc carrier in the amyloplast envelope (85). Subsequently, characterization of the ADP-Glc transporter has been reported for maize endosperm (89, 90), barley endosperm (91), and wheat endosperm (92). 

Starch. A complex polymer of glucose, used by plants and green algae to store surplus sugar for later use. 

Levin EY, BlochK (1964) Absence of sterols in blue-green algae. Nature 202 90-91 Lichtenthaler HK, Schwender J, Disch A, Rohmer M (1997) Biosynthesis of isoprenoids in higher plant chloroplasts proceeds via a mevalonate-independent pathway. FEBS Letters 400 271-274 Lichtenthaler HK (1999) The l-deoxy-D-xylulose-5-phosphate pathway of isoprenoid biosynthesis in plants. Ann Rev Plant Physiol Plant Mol Biol 50 47-65 Luo Y, Sternberg L (1991) Deuterium heterogeneity in starch and cellulose nitrate of CAM and C3 plants. Phytochemistry 30 1095-1098... 

Green algae a + b — Cellulose Starch Generally two Unicellular,... 

Many green algae (Chlorophyceae) contain starch which can be fractionated into amylose and amylopectins. The major polysaccharides, however, are polysaccharides in which at least some of the hydroxyl groups of the sugars are substituted by half ester groups. These compounds are... 

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