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EXCI 445 > Chapter 4- Energy > Flashcards

Chapter 4- Energy Flashcards

1
Q

what is energy ?

A

work capacity

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2
Q

what is work ?

A

force * distance

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3
Q

what is power ?

A

work/time

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4
Q

what is energy expenditure?

A

energy/time

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5
Q

what are the two energy expenditure unit ?

A

calorie and joule

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6
Q

what is a calorie ?

A

energy needed to raise the temperature of 1g of water by 1 degree Celsius

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7
Q

what is the difference between Cal and cal ?

A 
Cal = 1 kcal 
cal = 1 cal
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8
Q

what unit is on food labels for energy expenditure ?

A

it is written in cal, but actually represents kcal

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9
Q

how to convert cal into joules ?

A

1 cal = 4.186 J

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10
Q

in energy produced in humans, what is the proportion of it used for movement ? what happens to the remainder ? what does this show ?

A

20% for movement
80% for maintaining homeostasis
shows that body is not efficient at using energy

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11
Q

how is energy conserved in the human body

A

in the chemical bonds between proteins, fats, CHO

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12
Q

how do you determine the energy content of food ?

A

bomb calorimetry

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13
Q

explain the process of bomb calorimetry

A

combust food of a known weight (usually 1g) with high pressure oxygen tank
heat is produced and transferred through metal walls, heating up water bath in which the sealed food tank is in
rise in water temperature reflects the energy content

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14
Q

what is the main drawback of bomb calorimetry ?

A

it measures the gross yield, but not what we would necessarily absorb, therefore overestimates actual calories, and also no distinction is made between the different macromolecules

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15
Q

what measurement does bomb calorimetry give ?

A

gross energy value (yield)

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16
Q

in bomb calorimetry, if 2g food increase the temperature of 3L water by 4 degrees Celsius, how many calories ?

A

1 cal - 1g - water 1 deg C

here, 3L x 4 deg C=12
12/2g = 6kcal/g

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17
Q

what does energy content of carbs depend on ?

A

the carb type and its structure

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18
Q

what does energy content of fat depend on ?

A

structure of TG or FA, a long chain may have more

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19
Q

what does energy content of protein depend on ?

A

type of protein and nitrogen content
nitrogen does not provide energy, so the denser the protein the more energy per gram
the denser the nitrogen the less energy per gram

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20
Q

what are the Atwater factors ?

A

correction factors for energy content that take into account differences in digestibility.

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21
Q

what is the coefficient of digestibility ?

A

the percentage of food absorbed

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22
Q

what is the coef of digestibility of carbs ?

A

97%

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23
Q

what is the coef of digestibility of fat ?

A

95%

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24
Q

what is the coef of digestibility of protein ?

A

92%

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25
Q

in an avg diet, what is the energy content of carbs ?

A

4 kcal/g

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26
Q

in an avg diet, what is the energy content of fat?

A

9 kcal/g

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27
Q

in an avg diet, what is the energy content of protein ?

A

4 kcal/g

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28
Q

what is the direct way of measuring energy expenditure in humans ?

A

direct calorimetry

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29
Q

all biochemical processes end up in heat production. true or false ?

A

true

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30
Q

how is direct calorimetry similar to bomb calorimetry ?

A

in both cases, measuring heat production. in humans: all biochemical processes result in heat production. in food: you combust it to measure.
in both you will measure the change in water (found in top of chamber) temperature

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31
Q

describe direct calorimetry

A

closed chamber with coils with known amount of water flowing. increase of water temperature as person is in room will indicate to us energy expenditure

32
Q

how does air travel through chamber in direct calorimetry ?

A

carbon dioxide and water are filtered out before it reenters the chamber, and there is a constant oxygen supply

33
Q

what is the disadvantage of direct calorimetry ?

A

expensive and requires trained personnel

34
Q

why is it not ok to use direct calorimetry in sport ?

A

usually unsuitable

35
Q

what is closed-circuit spirometry ?

A

a way to measure energy expenditure in resting conditions
breathe through mouthpiece into a spirometer with 100% oxygen (nose clamped)
measure the difference in volume of CO2 and difference in O2

36
Q

what does indirect calorimetry count on ?

A

the energy for all biochemical reactions depend on O2 supply

37
Q

what is the formula for RER ?

A

VCO2/VO2

38
Q

what is a respiration chamber ?

A

measurement of complete energy balance. similar to chamber in direct calorimetry but without coils to measure heat exchange. carefully monitor flow of O2
CO2 produced is recorded

39
Q

how is a respiration chamber installation different from direct calorimetry ?

A

can be bed, etc

without coils to measure heat exchange

40
Q

why is the respiration chamber ideal to calculate energy balance ?

A

because food intake can be controlled and urine/ fecal matter collected

41
Q

what is the advantage of the respiration chamber

A

allows to control for everything, including energy loss through feces

42
Q

what is the disadvantage of the respiration chamber

A

expensive, not suited for vigorous exercise, and usually needs 24hrs so disruptive to life of participant

43
Q

how does canopy calorimetry work ?

A

patient lie down relaxed on a bed or on a comfortable couch, with the head under a transparent hood connected to a pump, which applies an adjustable ventilation through it. Exhaled gas dilutes with the fresh air ventilated under the hood and a sample of this mixture is conveyed to the analysers, through a capillary tube and analysed. Ambient and diluted fractions of O2 and CO2 are measured for a known ventilation rate, and O2 consumption and CO2 production are determined and converted into Resting Energy Expenditure

44
Q

what is canopy calorimetry used for ?

A

measuring resting energy expenditure

45
Q

what is a Douglas Bag ?

A

used for example in exercise tests, collect expired air at final minute of each stage
expired respiratory gases are collected on an inflatable airtight bag. After completion of any test using Douglas Bags, gas collected must be analysed for volume and composition

46
Q

what is substrate utilization ?

A

use of inherent differences between CHO, fat, and protein in order to obtain info about fuel utilization

RER= VCO2/VO2 and from there you can determine what fuel is being used mostly

47
Q

what are the assumptions in substrate utilization indirect calorimetry? (4)

A
  • protein is not an important energy fuel
  • all gas exchange occurs across the lungs, and what is expired represents oxidation processes in the tissues
  • O2 and CO2 are ideal gases
  • complete oxidation of CHO, fat, and protein needs different amounts of oxygen and different amounts of CO2
48
Q

what would be the RQ for a metabolism using 100% fat ?

A

0.7

49
Q

what is RQ?

A

respiratory exchange ratio

50
Q

what would be the RQ for a metabolism using 100% CHO?

A

1.0

51
Q

what are the 2 assumptions of RQ?

A
  • exchange of O2 and CO2 at mouth are equivalent to processes in tissues
  • valid at rest and during light to 85% VO2max exercise
52
Q

what is the formula of RQ ?

A

CO2 produced / O2 consumed

53
Q

how is the formula of RER (>1) different from RQ?

A

RER takes into account CO2 produced unrelated to metabolism (due to buffering or hyperventilation for example)

54
Q

what are 3 cases where you will see an RER (>1) that therefore differs from RQ?

A
  • hyperventilation: CO2 extracted from body
  • high intensity exercise: buildup of lactic acid, lactate binds to sodium bicardbonate and becomes carbonic acid ejected from lungs as CO2
  • lipogenesis (RER up to 5.6)
55
Q

explain the doubly labeled water technique

A

bolus dose of two stable isotopes of water (2H and 18O), used as tracers. 2H is lost from body in water, and 18O is lost in water and at C18O2 in breath. Therefore the difference between the two tracer excretion rates represents the CO2 production rate, and with knowledge of fuel mixture oxidized, you can calculate energy expenditure

56
Q

explain the technique of labeled biarbonate

A

infusion of labeled bicarbonate. any change in body’s CO2 production will result in change of the labeled CO2 isotope, so the change will indicate total CO2 production

57
Q

what are one pro and 2 cons of labeled bicarbonate

A

pro: inexpensive
con: needs fancy equipment and personnel

58
Q

explain the reliability of HR monitoring technique

A

HR has linear relationship with oxygen uptake at submax exercise, but not reliable at low or supramax levels

59
Q

what are the cons of HR monitoring technique ?

A

a lot of factors like temperature, anxiety, etc can influence it + not accurate

60
Q

why can’t HR monitoring technique work well at rest ?

A

bc emotions can easily influence HR without much change in oxygen uptake

61
Q

how do you use HR monitoring technique ?

A

figure out relationship at different stages between HR and VO2 and calculate

62
Q

generally what kind of bad calculation does the accelerometer do ?

A

underestimate energy ependiture

63
Q

what is a quick way to calculate energy needs per day (for BMR, no physical activity)?

A

23-24 kcal/kg/day

64
Q

how many kcal will very strenuous activities burn?

A

13 kcal/min

65
Q

what is the largest component of daily energy expenditure ? (60-75%)

A

resting metabolic rate

66
Q

what is basal metabolic rate

A

rarely used, developed to test over several hours lying down and not eating the lowest O2 uptake in resting conditions

67
Q

what is diet-induced thermogenesis ?

A

increase in energy expenditure above RMR for several hours after meal, as a result of digestion, absorption, etc

68
Q

what is the thermic effect of exercise ?

A

variable component of energy expenditure, voluntary component (exercise) and involuntary (shivering, fidgeting)

69
Q

what are the three components of energy expenditure ?

A

BMR
diet induced thermogenesis
thermic effect of exercise

70
Q

which variable of energy expenditure varies the most in sedentary or very active people ?

A

thermic effect of exercise

71
Q

what is energy balance ?

A

energy intake = energy expenditure

72
Q

what kind of energy balance does someone who wants to lose weight wish ?

A

negative

73
Q

what is a positive energy balance ?

A

intake > expenditure

74
Q

what are 6 things affecting energy balance ?

A

weight, body composition (lean mass more bioactive), sex, age, activity level, genetics

75
Q

what technique for energy needs do you use on an unlimited budget ?

A

direct calorimetry ?

76
Q

what technique for energy needs do you use on a budget ?

A

equations

EXCI 445 (13 decks)

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