Energy Metabolism Flashcards
what is the cellular source of energy
ATP
what does ATP do/ where does it come from? `
- sustains physical energy, anabolism, active transport
- supplied by the macronutrients in the diet
how many chemistry calories are in a food calorie
1000 chemistry calories = 1 food calorie
how many KJs are in 1 food calorie
1 food calorie = 4.18 KJ
describe positive energy balance
- weight gain/ obesity
- infertility
- increased blood lipids
- insulin resistance
describe negative energy balance
weight loss
- infection
- loss of performance
- reduced bone mass
what did Antoine Lavoisier do?
- compared heat produced by a genie pot with the production of co2
- ice calorimeter (heat produced estimated by the amount of ice that melts
- CO2 formed from the reaction between oxygen and organic matter
what did Justin Liebig recognize?
Justin Leigib recognized that protein, carbohydrates, and fats are oxidized by the body
what did max rubner do?
max rubner measured energy values of certain foods to determine caloric content
what is calorimetry
it is the measurement of heat production
- uses heat as an indicator of the amount of energy stored in the chemical bonds of food
what are the steps when carrying out bomb calorimetry
- dry and weight sample and place in enclosed chamber- with oxygen
- ignite the sample
- heat released is absorbed by the water and measured
what are the potential sources of error in terms of bomb calorimetry
- overestimate energy (we dont digest like a bomb calorimeter)
- doesn’t take into account energy needed for digestion/ absorption
what is the Atwater value for CHO
4 kcal/g
what is the Atwater value for fat
9 kcal/g
what is the Atwater value for protein
4kcal/g
what are Atwater values
physiological fuel values
- take into account incomplete digestion
why does fat provide more kcal per gram vs CHO or protein
the chemical structure of CHO, fat, and protein indfluence the heat combustion for macronutrients
describe the chemical structure of CHO
ratio of hydrogen to oxygen= 2:1
describe the chemical structure of protein
- has nitrogen, which contributes to gross energy
however, our bodies dont use nitrogen for energy
describe the chemical structure of lipids
- less oxidized than CHO and protein
- ratio of hydrogen to oxygen I much greater than 2:1
- lipids have lots of hydrogen atoms available for cleavage and oxidation for energy
what does the bomb calorimeter measure
the bomb calorimeter measures gross energy of a compound
what are the factors that affect heat combustion of fatty acids
- unsaturation (the more double bonds, the less energy provided by that molecule)
- chain length (the longer the chain, the more energy provided)
what is the heat increment of feeding (HIF)
- thermic effect of food
- energy used for digestion, absorption, distribution, and storage of nutrients
- is about 5-30% of daily energy usage
- used to determine net energy
what is net energy
net energy= metabolized energy - HIF
- supports basal metabolism, physical activity, growth, pregnancy, etc
how much energy is partitioned towards HIF
5-30% of the metabolized energy is used for basic digestion mechanisms
what are the 4 primary components to energy expenditure?
- basal metabolic rate (BMR)
- Thermic effect of food (HIF)
- physical activity energy expenditure (PAEE)
- thermoregulation (a minor contribution)
what tissued are most reflective of the BMR
muscle and bone
what is the equation used when calculating BMR
BMR= A * [M^0.75] kcal/day
- A= metabolically active tissue (for humans, A=70)
- M = body weight in Kg
what is kleibers law
(0. 75)
- a constant used for all vertebrates, invertebrates, and unicellular organisms when calculating BMR
what are the factors that can affect BMR
- genetics
- age
- sex
- tissue proportions
- temperature
how does genetics affect BMR
inheritance of a fast or slow metabolic rate
how does exercise affect BMR
exercise changes body tissue proportions
muscle uses more energy than fat
what does indirect calorimetry measure?
O2 intake, CO2 output
- energy- releasing reactions in the body depends on the use of oxygen
what does direct calorimetry measure?
Heat output
- measures the heat a person generates (total heat loss)
what is the issue with indirect calorimetry?
this method can not account for anaerobic processed (ie- production of lactic acid)
- hyperventilation
- masks are impractical
what is the issue with direct calorimetry
- expensive
- impractical
compare direct vs indirect calorimetry
<1% difference
very comparable
what is the respiratory quotient (RQ)
a ratio of metabolic gas exchange
provides information about:
- energy expenditure
- biological substrate being oxidized
what is the equation used when calculating RQ (respiratory quotient)
RQ= (CO2 produced)/(O2 consumed)
why do RQ values for macronutrients vary
differentiations in chemical composition mean that each macronutrient required a different amount of oxygen intake in relation to CO2 produced
ie- fats require almost three times as much oxygen (in comparison to carbs) to complete the digestion
