energy intake Flashcards
what is the first law of thermodynamics
Energy cannot be created or destroyed but only changed between different forms.
what energy do plants use and what do they use it for
Plants use solar energy to synthesise proteins, fats & CHOs.
what energy do animals use and what for
Animals depend on the chemical energy in these plant molecules, taken as food, as their energy source.
what is chemical energy used to perform
mechanical work, electrical work & chemical work.
what is 1 calorie
amount of heat required to raise temperature of 1g of water by 1degreeC.
what is 1 kilocalorie (1 kcal or 1 Calorie)
amount of heat required to raise temperature of 1kg of water by 1degreeC
convert 1 KJ to J
1 kilojoule (kJ) = 1000 J = 103 J
convert 1 MJ to J
1 megajoule (MJ) = 1,000,000 J = 106 J
convert 1kcal to KJ
1 kcal = 4.184 kJ
convert 1 JK to kcal
1 kJ = 0.239 kcal
what does capital or non capital C on calorie mean
When word calorie has a capital C were talking about kilocalories, when it has small c were talking about calories
what is the gross energy of food
Total chemical energy in food
chemical energy stored in the bonds of what
Protein + Carbohydrate + Lipids + Alcohol
gross energy can be measured using what
a bomb calorimeter (this changes energy into heat):
Organic material + O2 -> CO2 + H2O + oxides of N + S + heat (GE)
name the 2 types of bomb calorimetry and explain them
Ballistic
Temperature rise of metal jacket is measured directly.
Adiabatic
Water-cooled jacket, kept at constant temperature as sample burns.
More accurate than ballistic.
what is energy lost in
Faeces (microbes, undigested fibre)
Urine (incomplete oxidation of N to urea)
Combustible gases from microbial action: H2, CH4
how do u work out the metabolisable energy
ME = Gross energy minus urinary & faecal energy losses.
This is the E available to the body.
what is metabolizable energy
the energy we can used form the foods
what is the metabolizable energy per gram of fat
37KJ or 9kcal
what is the metabolizable energy per gram of protein
17KJ or 4kcal
what is the metabolizable energy per gram of carbs
16KJ or 3.75kcal
what is the metabolizable energy per gram of alcohol
29KJ or 7kcal
what is the metabolizable energy per gram useful for estimating
estimating E which can be obtained from food by healthy individuals on a normal diet
name factors affecting metabolizable energy
Gastro-intestinal disease (celiac disease)e.g. malabsorption by gut - Finger like projections (microvilli) become chopped and lost, due to attack from bodys immune system. so less absorption
Unusual diet composition e.g. sports supplements (such as protein supplements)
Renal disease e.g. increased protein loss in urine
(Protein in urine usually is very low but in renal disease more and larger proteins are lost in urine
Diabetes mellitus i.e. increased glucose loss in urine
Parenteral nutrition i.e. fed intravenously so no gut losses
High fibre diets i.e. low carbohydrate absorption
for accurate measure of metabolizable energy in an individual what needs measured
the energy content of the food, urine, and faeces by bomb calorimetry + volume of combustible gases (if possible).
what is energy balance
the relationship between energy intake and energy output.
Energy = Energy – Energy
Balance Intake Expended
what is positive energy balance
Energy intake > energy expenditure
what is negative energy balance
Energy intake < energy expenditure
Achievement of energy balance is driven by what
1st law of thermodynamics.
what happens to body stored if energy intake = energy expenditure
body stores remain constant
what can energy be stored as
fat, glycogen, or protein
