glucose molecule, close to the chains 1,6-alpha branching bonds. A second enzyme, phosphoglucan, water dikinase (PWD) phosphorylates the glucose molecule at the C-3 position. A loss of these enzymes, for example a loss of the GWD, leads to a starch excess (sex) phenotype, and because starch cannot be phosphorylated, it accumulates in the plastids. After the phosphorylation, the first degrading enzyme, beta-amylase (BAM) can attack the glucose chain at its non-reducing end. Maltose is released as the main product of starch degradation. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme, disproportionating enzyme-1 (DPE1), combines two maltotriose molecules. From this chain, a glucose molecule is released. Now, BAM can release another maltose molecule from the remaining chain. This cycle repeats until starch is degraded completely. If BAM comes close to the phosphorylated branching point of the glucose chain, it can no longer release maltose. In order for the phosphorylated chain to be degraded, the enzyme isoamylase (ISA) is required. The products of starch degradation are predominantly maltose and smaller amounts of glucose. These molecules are exported from the plastid to the cytosol, maltose via the maltose transporter, which if mutated (MEX1-mutant) results in maltose accumulation in the plastid. Glucose is exported via the plastidic glucose translocator (pGlcT). These two sugars act as a precursor for sucrose synthesis. Sucrose can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night. Properties Structure While amylose was thought to be completely unbranched, it is now known that some of its molecules contain a few branch points. Amylose is a much smaller molecule than amylopectin. About one quarter of the mass of stored starch in plants consist of amylose, although there are about 150 times more amylose than amylopectin molecules. Accumulated starch within plants is stored in semi-crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2 μm), potato starches have larger granules (up to 100 μm) and wheat and tapioca all in-between. Unlike other botanical sources of starch, wheat starch has a bimodal size distribution, with both smaller and larger granules ranging from 2 to 55 μm. Some cultivated plant varieties have pure amylopectin starch without amylose, known as waxy starches. The most used is waxy maize, others are glutinous rice and waxy potato starch. Waxy starches undergo less retrogradation,