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NUTR 3210 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What is ATP?

A
  • cellular source of energy
  • supplied by macronutrients in the diet
  • sustains physical energy, metabolism, active transport, etc.
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2
Q

What is a Calorie?

A

measure of heat to express the energy content of food

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3
Q

What is the conversion of a chemistry calorie vs a food calorie?

A

1000 chemistry calries = 1 food Calorie

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4
Q

What is the difference between calorie and Calorie?

A

calorie = chemistry
Calorie = food

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5
Q

What is the conversion of food Calorie to kcal to KJ?

A

1 food Calorie = 1 kcal = 4.18 KJ

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6
Q

What is the method used to estimate energy in foods?

A

Calorimetry = measurement of heat production

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7
Q

What is calorimetry?

A

Uses heat as an indicator of the amount fo energy stored in the chemical bonds of foods (carbon-hydrogen bonds), when these bonds are broken down, they release heat

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8
Q

What is bomb calorimetry?

A

works according to the principles of direct calorimetry (directly measures the amount of energy stored in chemical bonds of foods)

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9
Q

What are the steps to bomb calorimetry?

A
  1. dry and weigh sample (1g) and place in enclosed chamber (the bomb) with oxygen
  2. The sample is ignited
  3. heat that is released is absorbed by water and measured
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10
Q

What is the heat of combustion equal to?

A

Heat of combustion (gross energy) = maximum energy during a chemical reaction

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11
Q

What are the potential errors of bomb calorimetry?

A
  • overestimates energy (we don’t digest food like a bomb calorimeter burns it)
  • doesn’t take into account the energy needed for digestion and absorption
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12
Q

What are the physiological fuel values? (Atwater values)

A

CHO = 4
Fat = 9
Protein = 4

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13
Q

What is the formula for the physiological fuel values?

A

[Heat of combustion(gross energy) - energy lost in urine] x apparent digestibility
(a-b) x c

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14
Q

What are the units of the factors in the formula for physiological fuel values?

A

Heat of combustion(gross energy) = kcal/g
Energy lost in urine = kcal/g
Apparent digestibility = %

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15
Q

What are two other names for physiological fuel values?

A

available energy
metabolizable energy

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16
Q

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

A

The heat of combustion (kcal/g) describes the total energy released during a chemical reaction between a hydrocarbon and oxygen to release CO2 and H2O and heat. The chemical structure of CHO, fat and protein influences the heat of combustion for macronutrients
CHO - ratio of hydrogen to oxygen = 2:1
Protein - has nitrogen which affects gross energy measurement, however in the body, nitrogen combines with hydrogen and is eliminated as urea. This loss of hydrogen affects the heat of combustion
Lipid - lipids are less oxidized than CHO and protein, ratio of hydrogen to oxygen is much greater than 2:1, lipids have lots of hydrogen atoms available for cleavage oxidation for energy

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17
Q

What is stearic acid?

A

used for meat, poultry, fish, milk products, grains

18
Q

What is butyric acid?

A
  • SCFA
  • produced by gut bacteria
19
Q

What are the two factors that affect the 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 fatty acids)
20
Q

How to use the atwater values in a practical sense?

A

Can multiply the grams of the nutrient on the nutrition label by the atwater value for that nutrient and get the kcal

21
Q

What is heat increment of feeding?

A

(HIF)
- also called thermic effect of food
- energy used for the digestion, absorption, distribution and storage of nutrients
- comprises 5-30% of daily energy usage
- used to determine net energy

22
Q

What is the formula for net energy

A

Net energy = matabolizable energy - HIF

23
Q

What is net energy?

A

Supports basal metabolism, physical activity, growth, pregnancy

24
Q

What are the four components to energy expenditure?

A
  1. basal metabolic rate (BMR) - main driving force, basic energy needs, resp blood flow etc.
  2. Thermic effect of food (same thing as HIF) - absorption, metabolism of food
  3. Physical activity energy expenditure (PAEE) - varies from person to person, energy spent using voluntary muscles
  4. thermoregulation (energy spent maintaining body temp)
25
Q

How is BMR measured?

A
  • shortly after waking
  • done in a lab
  • come to lab before and sleep
  • post-absorptive state
  • lying down
  • completely relazed
  • comfortable room temperature
  • BMR = kcal per 24 hrs
26
Q

What tissues are most reflective of the BMR?

A

Muscle and bone

27
Q

What is the formula for BMR?

A

BMR = A x [M^0.75] kcal/day
A = metabolically active tissue (fat free mass, muscle and bone), the value for humans is 70
M = body weight in kg
0.75 = constant used for all vertebrates, invertebrates and even unicellular organisms

28
Q

What are factors that can affect BMR?

A
  • Genetics (inheritance of a fast or slow metabolic rate)
  • Age (young>old because of greater muscle mass)
  • Biological sex (men>women because of greater muscle mass)
  • Exercise changes body tissue proportions
    fat tissue (20% BW, 5% metabolic activity)
    muscle (30-40% BW, 25% metabolic activity)
    brain, liver, heart and kidney (5% BW, 60% metabolic activity)
  • temperature (maintaining thermoregulation
29
Q

Can you use body fat % to calculate BMR?

A

if you measure body fat %, you can have a more accurate measure of BMR

30
Q

Heat production can be used as a measure of ___________

A

energy expenditure

31
Q

What is the general combustion equation for indirect calorimetry?

A

Fuel + O2 ->(resp) CO2 + H2O + heat

Fuel - diet (CHO, protein, fat)
heat - direct cal
O2 and CO2 - indirect cal

32
Q

What is direct calorimetry?

A

Measures the heat a person generates; total heat loss, spend 24h in the chamber, very expensive and impractical

33
Q

What is indirect calorimetry?

A

energy releasing reactions in the body depending on the use of oxygen

34
Q

What does indirect calorimetry measure in order to estimate energy requirements?

A
  • oxygen consumption (L)
  • carbon dioxide production (L)
  • urinary nitrogen loss (g)
35
Q

What can indirect calorimetry not account for?

A

anaerobic processes

36
Q

What are the advantages and disadvantages of indirect calorimetry?

A

Disadvantages: hyperventilation, hard to get an airtight seal, masks are impractical, could give flawed measurements

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

37
Q

What is the respiratory quotient?

A
  • provides information about energy expenditure and biological substrate being oxidized
  • ratio of metabolic gas exchange
38
Q

What is the formula for the respiratory quotient?

A

RQ = CO2 produced/O2 consumed

39
Q

What nutrients are the main contribution of RQ?

A

assume CHO and fat

40
Q

Why does RQ vary for macronutrients?

A

Differences in chemical composition mean that each macronutrient requires a different amount of oxygen intake in relation to CO2 produced

41
Q

How to use the table to calculate RQ?

A

For each non-protein RQ value there is a caloric value for each L of O2 consumed or CO2 produced, table tells you how much CHO and fat contribute to energy

NUTR 3210 (17 decks)

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