Migratory birds are fat, really fat, especially before migration. Fresh duck bre
ID: 253807 • Letter: M
Question
Migratory birds are fat, really fat, especially before migration. Fresh duck breast meat is 40.0 % fat! This is one reason I am not fond of duck… However fat is an excellent and lightweight source of ATP energy for marathon flights. One surprise bonus is that complete oxidation of fats to water (and CO2 of course) means that they can fly great distances without stopping for water because they make their own (imagine running 1000 miles without a drink!). This is called “metabolic water.” Humans don’t make enough of this to break even because we eliminate wastes in watery urine but birds excrete dry-ish uric acid and so can save their water. Assume that with bones, beak, feathers, etc that a 5.0 lb duck is 30% w/w fat. Ducks have 50% saturated fat and 50% monounsaturated. For this calculation we will ignore the triacylglycerol’s 3C glycerol backbone and assume that the whole mass of the fat is fatty acids (50% stearic acid and 50% oleic acid).
- If when this duck finally lands it has entirely used up its fat stores, calculate how much metabolic water (in mL) has been produced. Show in DETAIL how you obtained your answer.
Explanation / Answer
Animal metabolism produces about 100 grams of water per 100 grams of fat.
A 5.0lb duck with 30% w/w fat would have 1.5lbs of fat
The fat when converted would produces about 680 grams of water.
Each mL of eater weighs 1g, so 680 grams of water would equal to 680mL of metabolic water produced.