3) Carbon Fixation : Carbon fixation is another example of anabolism because in photosynthetic organisms such as plants, cyanobacteria, algae and other photoautotrophic ogranisms fixate carbon dioxide into glycerate 3-phosphate which is then further converted into glucose. Beginning with photosynthesis, synthesis of carbohydrates from sunlight and carbon dioxide. This process uses ATP and NADPH produced by the photosynthetic reactions to convert CO2 into glycerate 3-phosphate. This shows anabolism because from a smaller simpler subunit of carbon dioxide, glycerate 3-phosphate is produced, a much larger and complex biochemical compound.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine . 
Some reactions take place in a single step. We can represent this using an energy profile . An activated complex (or transition state ) forms between reactant and product. This is not a 'real' substance in the sense that it can be isolated and put in a test tube. But based on various pieces of experimental evidence it is the chemist's model of how the reaction occurs. The energy 'hump' shows how much energy reacting molecules must have for a 'successful' collision, . one that leads to reaction. The formation of an activated complex requires energy to bring molecules together in the correct orientation. Therefore, it is always an endergonic reaction. The energy required is called the activation energy (E a ).