Answer:
1. orienting substrates; 2. the transition state; 3. R-groups
Step-by-step explanation:
Enzymes are the biocatalysts that serve to speed up the chemical reactions by lowering down the required activation energy. Activation energy is the energy required to make an unstable transition state from relatively stable substrates. Transition state formation requires a breakdown of some chemical bonds and reorientation of functional groups.
Enzymes serve to facilitate the formation of transition state by lowering down the activation energy. The reactions can occur at normal body temperature in the presence of enzymes. Enzymes are specific for their substrates which means that they allow binding of selected substrates to their active sites. Substrate specificity is determined by the interaction between the R groups of amino acids present in the active site with the functional groups of substrates.