The main difference between blood sugar and glucose is that blood sugar refers to the glucose carried to all of the cells in the body through the bloodstream, but glucose is a simple sugar, being the most abundant monosaccharide. Furthermore, blood sugar is the most important molecule in energy production through cellular respiration. Meanwhile, photosynthesis in plants is the biochemical reaction that synthesizes glucose, which is then stored in the form of starch in plants and glycogen in animals. 

Blood sugar refers to the main sugar found in the blood of humans and other animals, coming through the diet and serving as the main source of energy. Glucose refers to a simple sugar important as the main energy source in living organisms and is a component of many carbohydrates. 

Occurrence：Blood sugar only occurs in the blood of animals. But glucose, in animals, occurs in the blood and inside cells, and in plants, it occurs inside the cells.  

Significance：Blood sugar is the transport form of glucose in the body through the bloodstream, while glucose is a simple sugar, being the most abundant monosaccharide. 

Roles：Blood sugar is important in energy production through cellular respiration. But, glucose, produced by photosynthesis in plants, is stored in the form of starch in plants and glycogen in animals. 

Effect of them in Higher Levels：High levels of blood sugar levels result in hyperglycemia as well as diabetes mellitus, which is the persistent hyperglycemia. On the other hand, high levels of glucose, by serving as a monomer, lead to the synthesis of the common forms of polymers, such as cellulose and starch in plants and glucagon in animals. 

Conclusion：Glucose is the simplest and the most common monosaccharide in both plants and animals. In general, plants synthesize glucose through photosynthesis and store them in the form of starch, which is then used in cellular respiration. Blood sugar is a form of glucose, circulating in the bloodstream of animals. Its main function is to supply glucose for the cells in metabolizing tissues of the body. Thereby, glucose serves as the main source of energy for cellular respiration. Furthermore, excess glucose is stored in the form of glycogen in animals. Apart from that, glucose serves as the precursor for cellulose and many other carbohydrates. Hence, the main difference between blood sugar and glucose is their occurrence and importance. 

Sources: pediaa