Unit 4 NUTR 3210

what is ATP?

- cellular sources of energy supplied by macronutrients

- sustains physical energy, anabolism etc

what is a calorie?

- a measure of heat to express energy

- energy required to raise temp of 1 kg/L water by 1C

1 food Calorie = 1000 chemistry calories = 1 kcal = 4.18 KJ

what is calorimetry?

uses heat to indicate amount of energy stored in chemical C-H bonds of foods

how does a bomb calorimeter work?

- dry and weigh sample, place in chamber with oxygen

- ignite sample

- heat released absorbed by water

- heat of combustion (gross energy = max energy produced)

what are the potential errors with bomb calorimetry?

- overestimates energy (don't digest everything eg fibre)

- doesn't account for energy for digestion and absorption

why does fat provide more kcal/g vs CHO or protein?

- depends on macronutrient chemical structure

- fat less oxidized = greater ratio of H to O

- more H atoms available for cleavage and oxidation for energy

what are physiological fuel values?

- Atwater values, available energy, metabolizable energy

- CHO = 4 kcal/g

- fat = 9 kcal/g

- protein = 4 kcal/g

what factors affect the heat of combustion of FA?

- chain length: longer releases more energy

- degree of unsaturation: more DB means less energy released

what is the heat increment of feeding (HIF)?

- thermic effect of food, 5-30% of daily energy use

- energy use for digestion, absorption, distribution, and storage of nutrients

what is net energy?

- supports basal metabolism, physical activity, growth, pregnancy etc

= metabolizable energy - HIF

what are the primary components of total energy expenditure?

1. basal metabolic rate (BMR)

2. thermic effect of food (HIF)

3. physical activity energy expenditure (PAEE)

4. (thermoregulation)

what is basal metabolic rate?

- the energy required to sustain functions like breathing, BP, etc

- kcal per 24 hrs

- measured shortly after waking, lying down relaxed, post absorptive state

what do you need to know for Kleiber's Law?

BMR = A×[M^0.75] kcal/day

- metabolically active tissue = A = 70 for humans

- body weight = M to exponent 0.75

what do you need to know for the Harris-Benedict equation?

know sex, weight, height, age, physical activity

what is needed for the Katch-Mcardle equation?

- fat free mass (FFM)

what is direct calorimetry?

- measures the heat a person generates; total heat loss

- very expensive, impractical

what is indirect calorimetry?

estimates energy requirements by measuring

- oxygen consumption (L)

- carbon dioxide production (L)

- urinary nitrogen loss (g)

what are the pros/cons of indirect calorimetry?

- cons: hyperventilation, getting an airtight seal, masks impractical

- advantages: useful with animals, can determine the type of substrate being oxidized

what is the Respiratory Quotient (RQ)?

- ratio of metabolic gas exchange

- gives info about energy expenditure, what biological substrate being oxidized

- varies for macronutrients

- CO2 produced / O2 consumed

what are the assumptions for RQ?

- only CHO and fat are metabolized

- no synthesis happening at same time as breakdown

- amount of CO2 exhaled = amount of CO2 produced by tissues