Topics:
Animal Nutrition, Animal Refresher
Glucose Yield of Propionic Acid
1 gram of Propionic acid can theoretically provide ______ (g) of glucose.
- 1.23 g — Correct Answer
- 5.6 g
- 0.23 g
- 3.6 g
Explanation:
Correct Answer: 1.23 g glucose per gram propionic acid
Propionic acid (propionate) is the major gluconeogenic VFA in ruminants. Theoretically, 1 g of propionic acid yields 1.23 g of glucose via gluconeogenesis in the liver. This conversion is calculated from molecular weights: Propionate (74 g/mol) → Glucose (180 g/mol); ratio = 180/74/2 × 2 ≈ 1.23 g glucose per g propionate.
Propionic Acid → Glucose Pathway
| Step | Conversion |
|---|---|
| 1 | Propionic acid → Propionyl-CoA |
| 2 | Propionyl-CoA → Methylmalonyl-CoA |
| 3 | Methylmalonyl-CoA → Succinyl-CoA |
| 4 | Succinyl-CoA → OAA → PEP → Glucose |
VFA Roles in Ruminant Metabolism
- Acetate → milk fat synthesis (predominant VFA at 65%).
- Propionate → gluconeogenesis → milk sugar (lactose) synthesis.
- Butyrate → converted to β-hydroxybutyrate in rumen epithelium.
- VFAs provide ~70% of ruminant energy needs.
Why Other Options Are Wrong
- 5.6 g → far exceeds what is chemically possible from 1 g propionate.
- 0.23 g → too low; propionate is an efficient gluconeogenic substrate.
- 3.6 g → incorrect; 3.6 Mcal is the metabolic energy per kg TDN, not glucose yield from propionate.
📚 About this Topic — Animal Nutrition
This multiple choice question is from Animal Nutrition, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Nutrition to strengthen your preparation.
