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nutr 3210 > energy > Flashcards

energy Flashcards

1
Q

what is the cellular source of energy?

A

ATP

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2
Q

what is the energy value of a food?

A
  • calorie which is a measure of heat to express the energy content of food
  • 1 food calorie: energy required to raise the temp of 1 kg of water by 1 degree C
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3
Q

are chemistry calories and food calories the same?

A

no, 1000 chemistry calories = 1 food calorie = 1 kcal = 4.18 KJ

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4
Q

what is calorimetry?

A
  • measurement of heat production
  • uses heat as an indicator of the amount of energy stored in C-H bonds of foods
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5
Q

what is bomb calorimetry?

A
  • where a sample is ignited in a chamber and the heat released is absorbed by water and measured
  • measures gross energy
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6
Q

what is heat of combustion?

A

gross energy = the maximum amount of energy that will be produced

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7
Q

why does fat provide more kcal per gram than CHO or protein?

A
  • CHO ratio of H to O = 2:1
  • protein has N but it combines with H and is eliminated as urea; loss of H affects heat of combustion
  • lipids are less oxidized than CHO and protein, ratio of H to O is much greater than 2:1, lots of H for cleavage and oxidation for energy
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8
Q

what are the atwater values of CHO, fat, and protein?

A
  • CHO: 4
  • fat: 9
  • protein: 4
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9
Q

what are factors that affect heat of combustion of fatty acids?

A
  • chain length: longer chain length releases more energy
  • degree of unsaturation: the more double bonds, the less energy released for equivalent chain length FAs
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10
Q

how do you calculate the kcal of CHO, fat, or protein in a sample?

A

grams x atwater value kcal/g = kcal in sample

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11
Q

what is heat increment of feeding?

A
  • aka thermic effect of food
  • energy used for the digestion, absorption, distribution, and storage of nutrients
  • 5-30% of daily energy usage
  • used to determine net energy
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12
Q

how do you calculate net energy?

A

net energy = metabolizable energy - HIF

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13
Q

how do you calculate gross energy?

A

gross energy = kcal/weight in g

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14
Q

how do you calculate metabolizable energy?

A

metabolizable energy = gross energy x apparent digestibility

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15
Q

what is net energy?

A

energy that supports basal metabolism, physical activity, growth, pregnancy, etc.

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16
Q

what are the three primary components to energy expenditure?

A
  1. basal metabolic rate
  2. thermic effect of food/hif
  3. physical activity energy expenditure
    (thermoregulation)
17
Q

how is bmr measured?

A
  • shortly after waking, post absorptive/fasted state, lying down, completely relaxed, and comfortable room temperature
  • BMR = kcal per 24 hours
  • based on metabolic weight
18
Q

what is the A constant for humans when calculating BMR?

A

70

19
Q

what factors affect BMR?

A

genetics, age, sex, exercise, temperature

20
Q

what is indirect calorimetry?

A
  • estimates energy requirements by measuring oxygen consumption, carbon dioxide production, and urinary nitrogen loss
  • can’t account for anaerobic processes
21
Q

what are the disadvantages of indirect calorimetry?

A

hyperventilation, hard to get an airtight seal, masks are impractical

22
Q

what are the advantages of indirect calorimetry?

A

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

23
Q

what is the respiratory quotient?

A
  • ratio of metabolic gas exchange
  • provides info about energy expenditure and biological substrate being oxidized
24
Q

how do you calculate the respiratory quotient?

A

RQ = CO2 produced/O2 consumed

25
Q

what causes the respiratory quotient to vary?

A
  • differences in chemical composition
  • each macronutrient requires a different amount of oxygen intake in relation to CO2 produced
  • fate requires more O2 to oxidize than CHOs
26
Q

how do you determine energy expenditure per hour?

A

find RQ, look for caloric value on table, multiply corresponding caloric value by O2 or CO2 to get kcal/h

27
Q

how do you determine energy expenditure per hour?

A

find RQ, look for caloric value on table, multiply corresponding caloric value by O2 or CO2 to get kcal/h

nutr 3210 (5 decks)

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