Glycolysis

Topics: Adenosine triphosphate, Glycolysis, Cellular respiration Pages: 4 (818 words) Published: December 6, 2011
Glycolysis
Two stage process
Stage 1 – trapping and destabilising glucose in order to produce 2x3c molecules (5steps in the process). Requires energy (2 ATPs) Stage 2 – oxidation of the 3c molecules to pyruvate (5steps in the process). Energy generated (4tps and 2 NADH)

Stage 1
Step 1 – trapping glucose, glucose enters via facilitated diffusion through specific transport proteins. The family of transporters is known as GLUT, GLUT 3 (brain, nerve tissue) Low Km allows relatively constant rate of glucose uptake, GLUT 2 (liver, β-cells pancreas) high Km rate of uptake proportional to extracellular glucose concentration. GLUT4 (Muscle and adipocytes) rate of uptake controlled by insulin. Does not alter Km of the protein, but changes Vmax by increasing the number of transporters,. Number of GLUT4 transporters can be increased by exercise. Transporters are found in intracellular pods, when glucose levels rise, insulin is activated which creates a cascade of reactions which brings the pool of transporters to the surface leading to more uptake of glucose. Once in the cell glucose is trapped by phosphorylation. Glucose 6-phosphate is negatively charged and cannot diffuse out of the cell. Addition of the phosphate group begins the destabilisation process of glucose, which leads to further metabolism hexokinase

Can phosphorylate (kinase) a variety of hexose (six carbon) sugars (glucose, mannose even fructose) Induced fit enzyme action
Equilibrium of reaction strongly favours glucose 6-phospate (effectively irreversible reaction) Regulatory enzyme of glycolysis, inhibited by glucose 6-P (FEEDBACK INHIBITION)

Step 2 – formation of fructose 6-phosphate
Isomerisation of Glucose 6-P to Fructose 6-P is a completely reversible reaction carried out by the enzyme phosphoglucose isomerase. Convert from one isomer (glucose) to another (fructose) by Tautomerisation

Step 3 – second phosporylation reaction
The enzyme Phosphofructokinase carries out this reaction....
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