4 stages of aerobic respiration; 1) GLYCOLYSIS.

GLYCOLYSIS ( 4 stages)

STAGE 1 - ACTIVATION OF GLUCOSE BY PHOSPHORYLATION

• takes place in cytoplasm of cells
  
• begins with activation of main respiratory substrate (mainly hexose sugar - glucose)
• activation involves addition of 2 phosphate molecules provided by 2 molecules of ATP.
• the phosphate molecules come from HYDROLYSIS of 2 ATP molecules to ADP ------> this provides energy to activate glucose.
  
• the resultant activated molecule is known as PHOSPHORYLATED GLUCOSE

STAGE 2 - SPLITTING OF THE PHOSPHORYLATED GLUCOSE

• the phosphorylated glucose is split into 2 molecules called TRIOSE PHOSPHATE.
  

STAGE 3 - OXIDATION OF TRIOSE PHOSPHATE

• hydrogen is removed from both of the triose phosphate molecules and transferred to a hydrogen - carrier molecule known as NAD.

STAGE 4 - THE PRODUCTION OF ATP

• enzyme controlled reactions convert each triose phosphate molecule into 2, 3-carbon molecules called PYRUVATE.
• in the process, 2 molecules of ATP are regenerated from ADP.