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Once glucose enters the cell, the first step is phosphorylation of glucose by a family of enzymes called hexokinases to form glucose 6-phosphate (G6P). This reaction consumes ATP, but it acts to keep the glucose concentration inside the cell low, promoting continuous transport of blood glucose into the cell through the plasma membrane transporters.
In enzymology, a starch synthase (EC 2.4.1.21) is an enzyme that catalyzes the chemical reaction. ADP-glucose + (1,4-alpha-D-glucosyl) n ADP + (1,4-alpha-D-glucosyl) n+1 Thus, the two substrates of this enzyme are ADP-glucose and a chain of D-glucose residues joined by 1,4-alpha-glycosidic bonds, whereas its two products are ADP and an elongated chain of glucose residues.
Glycolysis can be regulated at different steps of the process through feedback regulation. The step that is regulated the most is the third step. This regulation is to ensure that the body is not over-producing pyruvate molecules. The regulation also allows for the storage of glucose molecules into fatty acids. [5]
The overall reaction can be expressed this way: [10] Glucose + 2 NAD + + 2 P i + 2 ADP → 2 pyruvate + 2 NADH + 2 ATP + 2 H + + 2 H 2 O + energy. Starting with glucose, 1 ATP is used to donate a phosphate to glucose to produce glucose 6-phosphate. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase.
Glycogen synthase (UDP-glucose-glycogen glucosyltransferase) is a key enzyme in glycogenesis, the conversion of glucose into glycogen. It is a glycosyltransferase ( EC 2.4.1.11 ) that catalyses the reaction of UDP-glucose and (1,4- α - D -glucosyl) n to yield UDP and (1,4- α - D -glucosyl) n+1 .
Glycogenesis is the process of glycogen synthesis or the process of converting glucose into glycogen in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose levels. [1]
Glucose reacts with oxygen in the following reaction, C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O. Carbon dioxide and water are waste products, and the overall reaction is exothermic. The reaction of glucose with oxygen releasing energy in the form of molecules of ATP is therefore one of the most important biochemical pathways found in living organisms.
As glucose enters a cell, it is immediately phosphorylated by ATP to glucose 6-phosphate in the irreversible first step. In times of excess lipid or protein energy sources, certain reactions in the glycolysis pathway may run in reverse to produce glucose 6-phosphate , which is then used for storage as glycogen or starch .