Give scientific reasons:
$(1)$ Krebs' cycle is an important process.
$(2)$ Sometimes an amphibolic pathway is seen in respiration.

(N/A) $(1)$ In aerobic respiration,the Krebs' cycle is essential for the complete oxidation of pyruvate derived from glucose. It generates high-energy electron carriers,specifically $NADH_2$ and $FADH_2$. These carriers subsequently donate electrons to the electron transport chain,facilitating the synthesis of $ATP$ through oxidative phosphorylation. Furthermore,the cycle provides intermediates for various biosynthetic pathways.
$(2)$ Respiration is traditionally viewed as a catabolic process involving the breakdown of glucose. However,it also serves as a source of precursors for the synthesis of other molecules. For instance,when fats are used as respiratory substrates,they are broken down into fatty acids and glycerol. Fatty acids are converted into acetyl $CoA$,which enters the Krebs' cycle. Conversely,when the cell needs to synthesize fatty acids,acetyl $CoA$ is withdrawn from the respiratory pathway. Since the respiratory pathway is involved in both the breakdown (catabolism) and the synthesis (anabolism) of substances,it is referred to as an amphibolic pathway.