Topic 63 - Combustion heat of nutrients, utilization of energy content of nutrients in the body

Question 1

Words to include in combustion of heat and nutrients

Answer 1

• Unit of energy: calorie
  
  • 1 calorie: amount enegy required to raise the temperatue of 1 gram of water by 1 degree celcius
• Calorie: measuring heat
• Joule: expressiono of all forms of heat and energy
• 1 calorie = 4.184 J
• Combustion heat of anutrient = amonut of heat yeald by buring of that particular nutrient
• Bomb calometers
  
  • Combustion heat of nutrients measurement
  • Complete oxidation
  • Law of Hess
    
    • Based on thermodynamics
• Heat equivalent of nutrients
  
  • Carbohydrates
    
    • Physical heat equvalent: 17 kJ/g
    • Physiological caloric value: 17 kJ/g
  • Fat
    
    • Physical heat equvalent: 39 kJ/g
    • Physiological caloric value: 39 kJ/g
  • Proteins
    
    • Physical heat equvalent: 22 kJ/g
    • Physiological caloric value: 17 kJ/g
    • Not entiely combusted
    • Metabolites of proteins in urine (urea)
• Acetic acid
• Propionic acid
• Butyric acid

Question 2

Words to include in utilization of energy content of nutrients

Answer 2

• Total energy, gross energy (GE) (Measured in bomb calometer)
  
  • Energy i feces
• Digestible energy (DE)
  
  • Fermentative energy
  • Energy in urine
• Metabolized energy (ME)
  
  • Net energy (NE)
  • Heat production, specific dynamic action

Question 3

Combustion of heat and nutrients

Definitions

Answer 3

• Unit of energy:; calorie
  
  • ​1 calorie: the amount of energy required to raise the teperature of 1 gram of water by one ˚C
• Calorie can only be used for measuring heat
• Joule can be used for the expression of all forms of heat and energy

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Question 4

Combustion of heat and nutriens

Measurement of heat (energy) content of nutrients

Answer 4

• Bomb calometer is used to determine the total heat content of a nutrient
  
  • Complete oxidation occurs
• Law of Hess: as long as the final products are the same, the steps on its way does not matter - the energy released during total oxidation will be the same

Question 5

Combustion of heat and nutrients

Heat equivalent of nutrients

Answer 5

• Combustion heat (calorie value) of a nutrient = amount of heat yield by burning of 1 g of that particular nutrient
• Combustion heat of carbohydrates and fats equals their physological caloric value
• Combustion heat of proteins is higher than the physological caloric value
  
  • Cause: Incompleteness of combustion of proteins, and final products of their degratation are (beasides CO₂ and H₂O) urea and other nitrogen containing compounds with high combustion heat
  • Products of protein metabolism still contain energy (eg. urea)

Question 6

Utlization of energy content of nutrients in the body

Answer 6

• Energy excreted in faces: 10-60% of total energy (depending on quality of food)
• Fermentative energy:
  
  • Ru: methane 5%
  • Energy in urine: 3-5%
• 70% of metabolized energy (ME) is utilized (used for vital processes)
  
  • Only 30-40% is turned to net energy (NE) (used for growth, production of meat or fats)
• Indigestibel components of nutrients leave the intestinal tract without being absorbed
• Birds: urine is excreted together with feces, and we can directly measure the metabolized energy
• Net energy is the difference between metabolized energy and the energy emitted from the body in the form of heat - specific dynamic action​
• Role of heat production and specific dynamic action:
  
  • ​Cover energy needs of vital processes
  • Utilized for production (milk, egg, wool, pregnancy growth)
  • External work