Bke2 Biochemistry Lectures

Lecture 22: Comparative metabolism
Reading material:

Abstract: In contrast to the monogastric animals, in ruminants only small amounts of glucose are absorbed and transported from the gastrointestinal tract to the liver. The microorganisms in the rumen ferment the carbohydrates to volatile fatty acids (VFA), acetate, propionate and butyrate.

Acetate is one of the most utilised substrates for energy production in most tissues. Propionate on the other hand is quantitatively the most important metabolite for glucose synthesis via the gluconeogenesis pathway. Keton bodies are normally produced in high concentration in the ruminant liver. Since no or very little glucose passes through the liver the enzyme activities of glucokinase are very low in ruminants, in comparison to monogastric animals. The triacylglycerols entering the rumen are degraded to glycerol and free fatty acids and the unsaturated fatty acids are saturated by the microorganisms in the rumen before being transported to the intestine for absorption. A large proportion of the food proteins are converted to microbial protein in the rumen.

Key concepts:
Glucose
Acetate
Propionate metabolism
Fat metabolism
Butyrate
Keton bodies
Gluconeogenesis

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