Question

Adipose tissue utilizes acetate to synthesize triglycerides. Why can cells not use acetate as a precursor for synthesizing glucose, as is seen in plants, bacteria and fungi?

Answer 1

animals lack glyoxysomes, the enzymes required for the conversion of acetate to glucose is present in the glyoxysomes, animals lack those enzymes.

Glyoxylate cycle starts with the formation of citrate from acetyl CoA and oxaloacetate, citrate is converted to isocitrate, then isocitrate lyase converts isocitrate to glyoxylate and succinate, the glyoxylate is then converted to malate by malate synthase, malate synthase uses acetyl CoA and glyoxylate to synthesize malate, the malate is then converted to oxaloacetate.

the succinate produced by isocitrate lyase is also converted to oxaloacetate, so the concentration of oxaloacetate increases, which can be used to make glucose.

since animals lack glyoxylate cycle animals cannot make glucose from acetate. in animals acetyl CoA is used in the TCA cycle, TCA cycle uses and regenerates oxaloacetate, so the amount of oxaloacetate remains constant, so animal cannot synthesize glucose from acetate.