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Physiology > Energy Balance > Flashcards

Energy Balance Flashcards

1
Q

Summarise catabolism/anabolism

A
  • Oxidation of carbohydrates, proteins + fats
    • Energy + CO2 + H2O produced
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2
Q

Catabolism

A
  • The reaction of energy supplying oxidation
  • Releasing utilisable energy
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3
Q

Anabolism

A
  • Synthesis of proteins, fats and carbohydrates from small molecules
  • This required energy
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4
Q

Released energy can be utilised as…

A
  • Heat
  • Energy
  • Work
    • Internal work
    • External work
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5
Q

Internal work

A
  • Chemical
  • Electric
  • Osmotic
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6
Q

External work

A

Mechanical work

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7
Q

Define 1 calorie

A

The energy required to raise the temperature of 1g water by 1°C

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8
Q

1 calorie = ? J

A

4.184 J

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9
Q

Which materials aren’t entirely combusted in the body?

A

Proteins

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10
Q

The heat content of nutrients can be measured in a…

A

Bomb calorimeter

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11
Q

The heat measured with a bomb calorimeter gives…

A

The maximum heat/energy that can be yielded from a particular nutrient in the body

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12
Q

Compare oxidation in the bomb calorimeter and in the animal body

A

Calorimeter:

  • Fast combustion
  • High temp.
  • Gaseous phase

In the body:

  • Slow, Gradual combustion
  • Low temperature
  • Liquid phase
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13
Q

Law of Hess related to energy combustion in the body

A
  • As long as the final products are the same
  • Energy released during oxidation = Energy in
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14
Q
A
  • 17kJ/g
  • 17kJ/g
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15
Q
A
  • 39kJ/g
  • 39kJ/g
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16
Q
A
  • 22kJ/g
  • 17 kJ/g

Physical heat equivalent > Physiological caloric value

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17
Q
A

14.6kJ/g

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18
Q
A

20.8 kJ/g

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19
Q
A

24 kJ/g

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20
Q

Why is protein combustion heat higher than its physiological caloric value?

A
  • Incompleteness of protein combustion
  • Urea is an additional product which has a relatively high combustion heat
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21
Q

Gross energy (GE)

A
  • Total energy of nutrients
  • Consumed by the animal
  • Measured in a bomb calorimeter
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22
Q

Digestible energy (DE)

A

Energy absorbed that doesn’t leave the body as faeces

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23
Q

% energy is lost through…

A
  • Faeces: 10%-60%
  • Urine: 3-5%
  • Methan: 5%
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24
Q

Energy lost with 1 mol of urea

A

634 kJ

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25
Q

1 mol of uric acid contains…kJ energy

A

1925 kJ

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26
Q

Digestible energy - energy in the urine =

A

Metabolisable energy

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27
Q

Net energy (NE)

A

The difference between:

  • Metabolised energy
  • Energy emitted from the body as heat
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28
Q

Energy balance of the body is assessed by measuring…

A

Heat turnover

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29
Q

Basal metabolic rate (BMR)

A
  • Energy production measured in an individual
  • In a complete resting state
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30
Q

Give the requirements of BMR measurement

A
  • Complete rest
  • Lying posture
  • No psychic excitement
  • Neutral environmental temperature
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31
Q

BMR equivalent in animals

A

Resting metabolic rate (RMR)

  • Measurements are taken:
    • Before morning feeding
    • Natural/experimental conditions
    • Animal at rest
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32
Q

Difference between basal and resting metabolic rate

A
  • Energy required for production
    • Specific dynamic action
    • Continuous utilisation of energy
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33
Q

Metabolic spectrum

A

Heat turnover that takes place above BMR/RMR

Depends on animal activity

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34
Q

Why is it difficult to measure metabolic spectrum?

A

Oxygen consumption doesn’t always reflex energy release

Anaerobic/aerobic respiration

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35
Q

Methods of direct calorimetry

A
  1. Method of lavoiser and laplace
  2. Complex direct calorimetry
  3. Compensation calorimetry
  4. Gradient calorimetry
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36
Q

Methods of indirect calorimetry

A
  • Open system
  • Closed system
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37
Q

Lavoisier and Laplace calorimeter

A
  • Chamber containing animal, surrounded by ice
  • Ice melted → water used to measure heat generation
  • 1g of ice melted = 0.334 kJ

Disadvantage: Neither expired/evaporated air is measured

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38
Q

Complex direct calorimetry

A
  1. In outer chamber, water of known temp. is circulated in a tube
  2. Heat from the animal warms the water
  3. Temp. of the water is measured
  4. Using this value and velocity of flow → Heat production calculated
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39
Q

Advantages of complex direct calorimetry

A
  • Considers emission of water vapour from the body
  • Energy turnover can be measured when in motion
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40
Q

When using complex direct calorimetry, total heat production is calculated by…

A

Measuring the amount of evaporated water from the body

This method uses water absorbent substances

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41
Q

The heat of water vaporisation

A

0.585 kcal/g

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42
Q

Compensation calorimetry

A
  1. 2 chambers with identical thermal capacity
  2. Animal placed into 1 chamber
  3. Electric bulb with a known output placed in the other
  4. Heat difference develops
  5. Lamp stays on until heat difference becomes equal
  6. Energy used by the bulb = output from the animal

1J = 1 Ws

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43
Q

Gradient calorimeter

A
  • Double walled chamber
    • Inner wall (Good conductor)
    • Outer wall (Constant temp.)
  • Heat dissipated through the wall is measured
    • So that heat difference between the two walls is registered
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44
Q

Summarise indirect calorimetry

A
  • O2 consumption is a reliable measure of energy turnover
  • Combustion of 1L oxygen releases 20.18 kJ
  • Measurement of the energy balance of large animals becomes possible
  • Amount of consumed oxygen is measured, energy balance is calculated
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45
Q

Disadvantage of indirect calorimetry

A
  • Restricted ability - Measures only O2 dependent energy production
  • During heavy activity, oxygen debt takes place
  • Released energy > amount of consumed oxygen
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46
Q

Open system indirect calorimetry

A
  1. Collect expired air
  2. Measure volume of expired air
  3. Determine:
    1. O2 values
    2. CH4 values (ru.)
    3. CO2 values
47
Q

Which device is used for open-system indirect calorimetry?

A

Douglas bag

  • Can be fastened to the back of the animal
48
Q

Closed system indirect calorimetry

A
  • The animal is isolated from atmospheric air
  • Inspirations are taken from a spirometer
    • Krogh’s device
  • Amount of consumed oxygen is measured
  • CO2 + H2 O are absorbed by natron
    • Only exhaled oxygen can return to the gas reservoir
49
Q

Which device can measure both CO2 and O2 consumption?

A

Knipping’s device

50
Q

Calculate respiratory quotient (RQ)

51
Q

Respiratory quotient

A
  • Varies between 0.7 and 1.0
  • Heat produced depends on what is combusted
  • The most heat is produced by combusting 1 L of oxygen
52
Q
A

RQ = 1

kJ/L oxygen = 21.1

53
Q
A

RQ = 0.82

kJ/L oxygen = 19.3

54
Q
A

Fat = 0.7

kJ/L oxygen = 19.8

55
Q

Why is RQ an approximate value?

A
  • CO2 production + O2 consumption can be modified by several factors other than metabolic
  • E.g in metabolic acidosis, RQ increases
    • Because resp. compensation of acidosis increases the expired CO2
56
Q

RQ value of hyperventilation

57
Q

RQ of metabolic acidosis

A

RQ increases

58
Q

RQ value of fattening

59
Q

RQ value of starvation

60
Q

C6H12O6 + 6 O2 = 6 CO2 + 6 H2O

Therefore…

61
Q

Give the average RQ value range for proteins

62
Q

The amount of oxidized carbohydrate, protein and fat can be approximated from…

A
  • Expired CO2
  • Inspired O2
  • Nitrogen excreted in the urine
63
Q

Value of RQ can be higher than 1 if…

A

Carbohydrate-fat transition occurs in the body

64
Q

During fattening, RQ values of between … and … can be detected

What is the cause?

A

1.31-1.6

  • Oxygen rich compound converted to oxygen poor compound
  • Utilised oxygen taken from the environment decreases
65
Q

Carbohydrate production during glycogenesis can give RQ values of…

A

0.4

E.g during fasting

66
Q

Why are metabolic reactions stoichiometric?

A

From a known quantity of oxygen, known CO2 and H2O values are produced

67
Q

RQ values are used for…

A

Providing information about the qualitative composition of energy sources (Carb. fat, protein)

68
Q

Atwater-rose respiratory calorimeter

A
  • Unification of indirect + direct calorimetry
  1. Animal placed in heat isolated chamber
  2. Increase of water temperature measured with velocity of water outflow

O2 consumption + CO2 production can also be measured

69
Q

List the factors influencing metabolism

A
  • Body size
  • Body surface
  • Neural/hormonal effects
  • Specific dynamic action
  • Temperature
  • Muscle work
  • Production
70
Q

Effect of body size on metabolism

A
  • Heat production increases with mass
  • Non-linear relationship
  • Absolute quantity of metabolism increases on a log-log chart
  • Metabolic rate related to body weight log decreases linearly
71
Q

Kleiber’s formula

A

BMR = k x body weight0.75

72
Q

Explain Kleiber’s formula

A

Metabolic rate is a function of the 0.75th power of body weight

73
Q

Effect of body surface area on metabolism

A
  • Logarithmic relation between body surface size and metabolism
74
Q

Body surface area =

A

k x body weight2/3​​

k = constant (between 0.09 - 0.12)

75
Q

Neural effects on metabolism

A
  • Somatic nervous system
    • Skeletal muscle
  • Sympathetic autonomic nervous system
    • Metabolic processes
76
Q

Hormonal effects on metabolism

A
  • Endocrine system
    • Thyroxine
    • Epinephrine
    • Growth hormone
77
Q

Thyroxine

A
  • Thyroid hormone
  • Increased secretion = Increased biological oxidation
  • Lack of thyroxine = BMR decreases 40%-60%
78
Q

Epinephrine

A
  • Causes increased metabolism of several organs
  • Direct action on hepatic glycogenolysis → Increased activity
79
Q

Male sex/growth hormone

A
  • Increase BMR by 15-20%
80
Q

Specific dynamic action effect on metabolism

A
  • BMR increase within an hour after eating
  • Lasts 2-3 hours
  • ‘Energy needed for the assimilation of that foodstuff in the body’
81
Q

Values for specific dynamic action for:

  • Protein
  • Carbohydrate
  • Fat
A
  • Protein = 30%
  • Carbohydrate = 5-7%
  • Fat = 5-10%
82
Q

Value of: Energy of digestion

83
Q

Value of: Energy needs of absorption and storage

84
Q

Value of: The process of hepatic deamination

85
Q

TEF

A

Thermic effect of food

86
Q

DIT

A

Dietary-induced thermogenesis

87
Q

Effect of temperature on metabolism

A
  • Change the velocity of chemical reactions
  • Common change causes:
    • Excessive muscular work
    • Fever
88
Q

Metabolism of homeothermic species as a function of environmental temperature

89
Q

Metabolism of homeothermic species as a function of the distance from the equator

A

Metabolism higher in cold zones

90
Q

Temp. change both:

  • Under lower critical temperature
  • Over upper critical temperature
A

Induces an increase in metabolism

91
Q

Effect of activity/productivity on metabolism

A
  • An increase of muscular activity increases metabolism
  • In horses:
    • Gallop: Max metabolism = RMR x (5-10)
    • Full gallop: Max metabolism = RMR x (35-40)

Heavier animals require a higher increase in metabolism

92
Q

Effects of production on metabolism

A
  • Animals making products require high amounts of energy
    • Eggs/milk etc
93
Q

Which species is the most efficiently producing?

94
Q

Which species is the least efficiently producing?

A

Beef cattle

25%

95
Q

Metabolism of proteins

A
  • Decomposed to amino acids
  • Amino acids → Transamination + Desamination
96
Q

Why is the composition of foodstuffs less important for ruminants?

A

Bacteria of the rumen can synthesise essential amino acids

97
Q

Virtual protein digestibility

A

LPD = ((Pt-Pe)/Pt)*100

  • Pt = total protein of food*
  • Pe = excreted protein*
98
Q

Why doesn’t virtual protein digestion provide a clear picture of digestibility of protein?

A

Protein leaving the body can be originated not only from food but from secretions of digestive glands

99
Q

True protein digestibility

A

TPD = (Pt-(Pe-Pend)/Pt)*100

Pend = Endogenous nitrogen (protein) excretion

100
Q

Net protein utilisation =

A

NPU = ((Nt-(Nf-Nend)-(Nu-Nend))/Nt)*100

  • Nt = total nitrogen in the food*
  • Nf = nitrogen loss via vaeces*
  • Nu = nitrogen loss via urine*
  • Nend = endogenous nitrogen in the faeces or urine*
101
Q

Summarise NDU

A
  • % of foodstuff protein entering the body
  • Does not differentiate between absorption and amino acid utilisation
102
Q

Which factors determine the value of NPU?

A
  • True digestibility (TD)
  • Biological availability (BA)
    • Give information whether protein is absorbed into the body’s proteins or not
103
Q

The value of true protein digestibility is between…

A

0-1%

E.g 0.9% digestibility coefficient = 90 protein digestibility

104
Q

What is used as a 100% standard of NPU?

A

Egg-white (Ovalbumin)

105
Q

Energy balance is the balance of…

A
  • Energy in
  • Energy out
106
Q

Energy in

A
  • Food
  • ~2100kCal
  • Anabolic hormones
    • Insulin
    • Sex steroids
    • TH, GH (PRoteins
107
Q

Energy out

A
  • BMR
  • Physical activity
  • Specific dynamic action of food
    • Growth, pregnancy, stress illness
  • Catabolic hormones
108
Q

How to lose weight

A

Energy in:

  • Decrease food intake

Energy out:

  • Increase BMR
  • Increase physical activity
109
Q

Good way of decreasing food intake

A
  • Change lifestyle
  • Food with big space-filling capacity with low calories
110
Q

Bad ways of decreasing food intake

A
  • Using backdoors of the central regulation of food intake (pills)
  • Orexigenic/anorexigenic factors
111
Q

Good ways to increase BMR

A
  • Decrease lean body mass (Muscle)
  • Lower environmental temperature
  • Moderate use of thermogenic substances
    • Coffee
    • Chilli
    • Black pepper
112
Q

Bad ways to increase BMR

A
  • Smoking
  • Overuse of thermogenic substances
  • TH stimulating drugs
113
Q

Effects of increased physical activity

A
  • Physical activity < 20% of BMR
  • Calorie burning effects:
    • During activity:
      • 30 minutes running = 1 candy bar
    • After activity:
      • O2 debt
      • Long term changes in the body (lean body mass)

Physiology (18 decks)

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