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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
1 mol of uric acid contains...kJ energy
1925 kJ
26
Digestible energy - energy in the urine =
Metabolisable energy
27
Net energy (NE)
The difference between: * Metabolised energy * Energy emitted from the body as heat
28
Energy balance of the body is assessed by measuring...
Heat turnover
29
Basal metabolic rate (BMR)
* Energy production measured in an individual * In a complete resting state
30
Give the requirements of BMR measurement
* Complete rest * Lying posture * No psychic excitement * Neutral environmental temperature
31
BMR equivalent in animals
Resting metabolic rate (RMR) * Measurements are taken: * Before morning feeding * Natural/experimental conditions * Animal at rest
32
Difference between basal and resting metabolic rate
* Energy required for production * _Specific dynamic action_ * Continuous utilisation of energy
33
Metabolic spectrum
Heat turnover that takes place above BMR/RMR Depends on animal activity
34
Why is it difficult to measure metabolic spectrum?
Oxygen consumption doesn't always reflex energy release ## Footnote *Anaerobic/aerobic respiration*
35
Methods of direct calorimetry
1. Method of lavoiser and laplace 2. Complex direct calorimetry 3. Compensation calorimetry 4. Gradient calorimetry
36
Methods of indirect calorimetry
* Open system * Closed system
37
Lavoisier and Laplace calorimeter
* Chamber containing animal, surrounded by ice * Ice melted → water used to measure heat generation * 1g of ice melted = 0.334 kJ ## Footnote *Disadvantage: Neither expired/evaporated air is measured*
38
Complex direct calorimetry
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
39
Advantages of complex direct calorimetry
* Considers emission of water vapour from the body * Energy turnover can be measured when in motion
40
When using complex direct calorimetry, total heat production is calculated by...
Measuring the amount of evaporated water from the body ## Footnote *This method uses water absorbent substances*
41
The heat of water vaporisation
0.585 kcal/g
42
Compensation calorimetry
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 ## Footnote *1J = 1 Ws*
43
Gradient calorimeter
* 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
44
Summarise indirect calorimetry
* 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
45
Disadvantage of indirect calorimetry
* Restricted ability - Measures only O2 dependent energy production * During heavy activity, oxygen debt takes place * Released energy \> amount of consumed oxygen
46
_Open_ system indirect calorimetry
1. Collect expired air 2. Measure volume of expired air 3. Determine: 1. O2 values 2. CH4 values (ru.) 3. CO2 values
47
Which device is used for open-system indirect calorimetry?
Douglas bag * *Can be fastened to the back of the animal*
48
Closed system indirect calorimetry
* 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
Which device can measure both CO2 and O2 consumption?
Knipping's device
50
Calculate respiratory quotient (RQ)
51
Respiratory quotient
* 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
RQ = 1 kJ/L oxygen = 21.1
53
RQ = 0.82 kJ/L oxygen = 19.3
54
Fat = 0.7 kJ/L oxygen = 19.8
55
Why is RQ an _approximate_ value?
* 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
RQ value of hyperventilation
RQ =2
57
RQ of metabolic acidosis
RQ increases
58
RQ value of fattening
RQ \> 1
59
RQ value of starvation
RQ \< 0.5
60
C6H12O6 + **6** O2 = 6 CO2 + **6** H2O Therefore...
RQ = 6/6
61
Give the average RQ value range for proteins
0.82-0.85
62
The amount of oxidized carbohydrate, protein and fat can be approximated from...
* Expired CO2 * Inspired O2 * Nitrogen excreted in the urine
63
Value of RQ can be higher than 1 if...
Carbohydrate-fat transition occurs in the body
64
During fattening, RQ values of between ... and ... can be detected What is the cause?
1.31-1.6 * *Oxygen rich compound converted to oxygen poor compound* * *Utilised oxygen taken from the environment decreases*
65
Carbohydrate production during glycogenesis can give RQ values of...
0.4 E.g during fasting
66
Why are metabolic reactions stoichiometric?
From a known quantity of oxygen, known CO2 and H2O values are produced
67
RQ values are used for...
Providing information about the qualitative composition of energy sources (Carb. fat, protein)
68
Atwater-rose respiratory calorimeter
* 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
List the factors influencing metabolism
* Body size * Body surface * Neural/hormonal effects * Specific dynamic action * Temperature * Muscle work * Production
70
Effect of body size on metabolism
* 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
Kleiber's formula
**BMR = k x body weight0.75**
72
Explain Kleiber's formula
Metabolic rate is a function of the 0.75th power of body weight
73
Effect of body surface area on metabolism
* Logarithmic relation between body surface size and metabolism
74
Body surface area =
k x body weight2/3​​ k = constant (between 0.09 - 0.12)
75
Neural effects on metabolism
* Somatic nervous system * Skeletal muscle * Sympathetic autonomic nervous system * Metabolic processes
76
Hormonal effects on metabolism
* Endocrine system * Thyroxine * Epinephrine * Growth hormone
77
Thyroxine
* Thyroid hormone * Increased secretion = Increased biological oxidation * Lack of thyroxine = BMR decreases 40%-60%
78
Epinephrine
* Causes increased metabolism of several organs * Direct action on hepatic glycogenolysis → Increased activity
79
Male sex/growth hormone
* Increase BMR by 15-20%
80
Specific dynamic action effect on metabolism
* BMR increase within an hour after eating * Lasts 2-3 hours * 'Energy needed for the assimilation of that foodstuff in the body'
81
Values for specific dynamic action for: * Protein * Carbohydrate * Fat
* Protein = 30% * Carbohydrate = 5-7% * Fat = 5-10%
82
Value of: Energy of digestion
20%
83
Value of: Energy needs of absorption and storage
20%
84
Value of: The process of hepatic deamination
60%
85
TEF
Thermic effect of food
86
DIT
Dietary-induced thermogenesis
87
Effect of temperature on metabolism
* Change the velocity of chemical reactions * Common change causes: * Excessive muscular work * Fever
88
Metabolism of homeothermic species as a function of environmental temperature
89
Metabolism of homeothermic species as a function of the distance from the equator
Metabolism higher in cold zones
90
Temp. change both: * Under lower critical temperature * Over upper critical temperature
Induces an increase in metabolism
91
Effect of activity/productivity on metabolism
* 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
Effects of production on metabolism
* Animals making products require high amounts of energy * Eggs/milk etc
93
Which species is the most efficiently producing?
Hen 49%
94
Which species is the least efficiently producing?
Beef cattle 25%
95
Metabolism of proteins
* Decomposed to amino acids * Amino acids → Transamination + Desamination
96
Why is the composition of foodstuffs less important for ruminants?
Bacteria of the rumen can synthesise essential amino acids
97
Virtual protein digestibility
**LPD = ((Pt-Pe)/Pt)\*100** * Pt = total protein of food* * Pe = excreted protein*
98
Why doesn't virtual protein digestion provide a clear picture of digestibility of protein?
Protein leaving the body can be originated not only from food but from _secretions of digestive glands_
99
True protein digestibility
**TPD = (Pt-(Pe-Pend)/Pt)\*100** *Pend = Endogenous nitrogen (protein) excretion*
100
Net protein utilisation =
**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
Summarise NDU
* % of foodstuff protein entering the body * Does not differentiate between absorption and amino acid utilisation
102
Which factors determine the value of NPU?
* True digestibility (TD) * Biological availability (BA) * Give information whether protein is absorbed into the body's proteins or not
103
The value of true protein digestibility is between...
0-1% ## Footnote *E.g 0.9% digestibility coefficient = 90 protein digestibility*
104
What is used as a 100% standard of NPU?
Egg-white (Ovalbumin)
105
Energy balance is the balance of...
* Energy in * Energy out
106
Energy in
* Food * ~2100kCal * Anabolic hormones * Insulin * Sex steroids * TH, GH (PRoteins
107
Energy out
* BMR * Physical activity * Specific dynamic action of food * + Growth, pregnancy, stress illness * Catabolic hormones
108
How to lose weight
Energy in: * Decrease food intake Energy out: * Increase BMR * Increase physical activity
109
Good way of decreasing food intake
* Change lifestyle * Food with big space-filling capacity with low calories
110
Bad ways of decreasing food intake
* Using backdoors of the central regulation of food intake (pills) * Orexigenic/anorexigenic factors
111
Good ways to increase BMR
* Decrease lean body mass (Muscle) * Lower environmental temperature * Moderate use of thermogenic substances * Coffee * Chilli * Black pepper
112
Bad ways to increase BMR
* Smoking * Overuse of thermogenic substances * TH stimulating drugs
113
Effects of increased physical activity
* 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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