Lecture 4 - Energy Metabolism Flashcards
What is the cellular source of energy
ATP
What is the energy value of a food
calorie is a measure of heat to express the energy content of food
What is the term for measurement of heat production
calorimetry
What is bomb calorimetry
dry weighed sample is placed in the enclosed chamber of the bomb calorimeter, the sample is ignited, heat released is absorbed by water and measured
What is heat of combustion
heat of combustion (gross energy) = maximum energy
What is the error with bomb calorimetry
overestimates energy
What are the Atwater values for carbs, fats, and proteins
carbs = 4
fats = 9
protein = 4
Why does fat provide more energy than carbs or protein
lipids are less oxidized (they have less oxygen) and the ratio of hydrogen to oxygen is higher
What factors effect heat of combustion of fatty acids
chain length and degree of unsaturation (double bonds)
- the longer the chain, the more energy released
- the more unsaturated, the less energy released
What is heat increment of feeding
also called the thermic effect of food*
energy used for digestion, absorption, distribution, and storage of nutrients
comprises of 5-30% of daily energy usage
used to determine net energy
What is net energy
metabolizable energy - HIF = net energy
What are the three primary components of energy expenditure
basal metabolic rate (BMR)
thermic effect of food (HIF)
physical activity energy expenditure (PAEE)
(and also thermoregulation - not looked at as much)
How is BMR measured
shortly after waking, in post-absorptive state
lying down
completely relaxed
comfortable room temperature
What tissues are most reflective of BMR
muscle and bone tissues
What is the equation for BMR
BMR = A x [M^0.75] kcal/day
where A is metabolically active tissue - value for humans is 70 but it differs per species
and M is mass
What factors can affect BMR
genetics
age
biological sex
exercise
temperature
What is direct calorimetry
measures the heat a person generates, total heat loss
- very expensive
- very impractical
What is indirect calorimetry
energy-releasing reactions in the body depend on the use of oxygen
- estimates energy requirements by measuring oxygen consumption, carbon dioxide production, and urinary nitrogen loss
What is respiratory quotient
provides info about energy expenditure and biological substrate being oxidized
- ratio of metabolic gas exchange
What is the equation for RQ
RQ = CO2 produced/O2 consumed
