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83 Cards in this Set
- Front
- Back
what is a calorie |
amount of heat required to raise one g of water by 1 degree C 1Cal=1kcal=1000cal will raise 1kg by 1C, 1kcal-4.18kj (energy expended applying a newton of force but this isnt really applicable) |
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what are examples of work requiring ATP |
-physical activity (muscle contraction) -anabolic pathways (making large molecules from smaller ones) -active transport systems (like the Na-K-ATPase pump) -cell division/growth/reproduction (mitosis, meiosis, DNA synthesis) |
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what does ATP do |
-predominant source of energy at the cellular level -utilizing during biochemical or physical work -degradation of proteins to things like CO2 will cause some energy to be caught by ATP (catabolic) -ATP pools supported by dietary macronutrient intake -ATP hydrolysis releases heat and energy trapped in bonds driving metabolic rxns and physical movement |
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what are the three main ideas of energy metabolism |
1. energy is the capacity to do metabolic or physical work 2. at the cellular level ATP is the predominant energy source and pools are supported by dietary macronutrient intake 3. energy value of foods is represented by calories/Calories |
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what do we need to generally know to understand and quantify energy intake |
-obligatory losses that occur as substrates are moved through various types of metabolism -caloric values of macronutrients |
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what do we generally need to quantify to understand energy expenditure (energy out) |
-physiology of heat production and how it can be measured by O2 intake or CO2 release |
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what are dietary fats used for |
make membranes, storage triglycerides, cholesterols etc |
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what are dietary carbs used for |
storage glycogen, glycoprotein and glycolipids which will all be oxidized to make energy |
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what are dietary proteins used for |
source of aa to make own protein and enzymes |
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Calories on a nutrition label refers to what |
metaboloizable energy |
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what is the defintion of energy expenditure |
the difference between energy taken up and energy expended (ie if a person does not consume as much energy as they take in they will lose body energy; not the same a losing weight: after exercise fat may decrease but lean muscle which weighs more so energy has decreased but body mass has increased) |
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what did lavoisier do |
invented an ice calorimeter to use the latent heat of fusion of water to estimate how much heat an animal was using |
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who recognized that proteins, fats and carbs are oxidized in the body |
von leibig |
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who measured energy values |
rubner |
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what did atwater do |
studied disgestion and defined metabolizeable energy that we will use today |
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what is the difference between cellular respiration |
cellular respiration creates atp (plus heat) on top of the combustion rxn that creates heat, CO2 and H2O |
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what are the products of food oxidation |
CO2, H2O, heat |
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what is the key point of cellular respiration |
aout 60% of energy will be lost as heat and 40% can be temporatily stored as ATP, which is later used in heat releasing rxns -total heat released in combustion and cellular respiration will be the same |
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what happens to food after we ingest it |
-extract nutrients which enter the bloodstream to do work -oxygen is inhaled and CO2 is released trlating to ATP production -any indigestible matter will be excreted as feces -heat is produced as one of the ultimate products of metabolism |
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what is cellular respiration as it relates to gross energy |
repiratory gas echange is a slow combustion and gross energy is the energy of combustion of all the food components into CO2 |
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where does metabolizeable energy come from |
oxidation via glycolysis and the TCA |
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what does bomb calorimetry do |
measures the gross energy contained in the the food by completely combusting it, releasing the heat that is used to measure an estimate of the potential energy stored in these foods |
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what does gross energy represent |
the total amount of energy that can be obtained by complete metabolic oxidation or chemical combustion. overrepresentation of available energy |
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which provides more information, direct or indirect calorimetry |
indirect, which measures overall oxygen intake and CO2 release as indirect measurements of heat/water vapour produced by the human body |
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how does a bomb calorimeter work |
an outer chamber is filled with water and an inner chamber contains a food sample. a wire connects the outer chamber and the food sample, and the inner chamber is filled with oxygen via the oxygen valve at high pressure. the wire is used to ignite the food sample in the presence of oxygen and heat released is measured by the deltaT in the water |
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what type of calorimtery do bomb calorimeters provide |
direct: provides gross energy |
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what must you do before to prepare the sample in bomb calorimetry |
weigh and dry the sample, place it in the inner chamber in contact with the wire |
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measuring heat in bomb calorimetry |
measure heat trapped by stainless steel chamber and the deltaT of the water which directly reflects heat liberated by the sample due to the isolation of the chamber |
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at what stages are feces, urine and gasses lost in metabolism |
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explain the energy loss diagram |
from gross energy, not all energy is able to be digested. insoluble fibres are an example, they are lost as feces, leaving digestible energy. from digestible energy there are obligatory losses in the urine, mainly protein in the form of urea, and also as gasses which are typically ignored, leaving us with the ME, then to get to NE must subtract HIF to obtain how much energy is left for basal metabolism, growth, development etc |
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what are atwater physiological values used for |
multiply by the grams of macronutrients to get ME for that macro |
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what would an example of urinary loss of a different macronutrient that isnt protein be |
loss of glucose in poorly controlled diabetics which would cause the ME for CHO to fall below 4 |
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what is significant about the combustion of human urine |
will produce 1.25 kcal for every g of protein consumed, must subtract from digestible energy to get ME |
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what are the atwater values |
P: 4 (due to excretions) CHO: 4 F: 9 |
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rank the macronutrients from most to least digestable |
CHO is more digestable than fat which is more digestable than protein |
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how to arrive at ME |
multiply GE (value from direct calorimetry) by percent digestability and arrive at the ME |
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what is the combustion habit of fully saturated organic molecules like methane |
no inherent oxidation, so there is a high potential for oxidation and combusts with a lot of heat energy like an FA. however, if you partially oxidize gasoline to yeild a product similar to methanol it will burn more slowly, like a CHO |
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methanol and CHOs have _______ inherent oxidation |
some (arent fully saturated) |
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rank the macronutrients from most to least oxidized |
fats then proteins then CHO, so less oxidation is available= less energy available |
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where is a fully oxidized C on an FA |
carboxyllic end |
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why is the stearic acid GE similiar to the atwater value for it |
it is a common dietary fat |
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what is the effect of longer chains on FA oxidation |
lower oxygen ratio making higher energy potential |
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why does butyric acid have such a low GE |
it is only a four carbon chain so when one (the carboxyllic carbon) is oxidized it is a small 3:1 ratio |
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what is the most consistent atwater fraction |
CHO |
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how to convert from GE to DE to ME for protein |
multiple GE by digestability coefficient then subtract (1.25 x g of protein) to arrive at ME |
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why do companies ask to remove the amount of insoluble fibre from the total energy expenditure |
to seem more attractive to consumers |
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what do Calories reflect on the nutrition label |
atwater physiological values- total of (9xg fat)+(4xgprotein)+(4xgCHO) |
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why may the ME calculation for CHO match up with the nutrition label |
since dietary fibre is roughly the same is insoluble fibres (not digested in SI) it does not provide significant VFA energy so it is hard to tell if we should keep it in the nutr facts label, however atwater including these in his calculations so they have been partially corrected for already - also no govt oversight so can be due to fibre amendment, intentional misrepresentation or mistakes |
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what is the net energy equuation |
ME-HIF=NE |
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what is HIF |
heat increment feeding; obligatory energy expenditure |
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where is HIF energy expended |
digestion, absorption and distribution of nutrients throughout the body (eg VLDL synthesis, chewing, gut motility, active transport of sodium and glucose molecules, gut and liver metabolism) and further metabolism, eg catabolism of excess amino acids after a high protein meal to prevent high levels of circulating blood protein |
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what is the NE |
supports basal metabolism, pregnancy and growth etc) |
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how much of a meal does the HIF take up |
5-15% (fat- 5, cho-10, protein-15) - a high protein meal will have a larger HIF than |
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what is the avg BMR for an adult |
1800kcal/day (75/hr) |
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when does energy expenditure peak |
about two hours after a meal, then goes back to baseline BMR |
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what is the graphic interpretation of energy expenditure |
area under curve but above the resting BMR line |
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what is another term for HIF |
thermic effect of food |
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what are the four components of energy expenditure |
HIF Basal metabolism physical energy expenditure thermoregulation |
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which has the highest use the NE after subtracting for HIF (~10%) |
BMR takes up about 60% then phys. (30%) and thermoreg (10%) |
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what is basal metabolic rate |
-if a person is only consuming enough Cal to meet their BMR then they will struggle to do physical work -measure of energy spent: shortly after waking, in a post absorptive (fasting state) for 12hrs to avoid HIF expenditure - lying down comfortably and relaxed but not asleep - in a comfortably warm/cool room such that no thermoregulation is needed -related to nonfat mass bc little metabolic activity in adipose tissue -NOT A PHYSICAL CONSTANT; WILL DROP DURING PERIODS OF STARVATION [tend to be in a negative energy balance]; regulated by the hypothalamus, thalamus, pituitary and thyrmoid hormone signalling axis -assumed to be an ongoing commitment when subject isnt engaged in phys. act. or thermoreg |
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how can physical activity and individual characteristics affect BMR |
professional atheltes and other very physical people may have higher BMR -sedentary modern lifestyle |
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how has the energy requirement for thermoregulation changed over the years |
with AC and heating humans dont need to spend as much energy on thermoregulation -cold temperatures may cause brown fat activation causing weight loss - thermal heat stress can cause beneficial effects on cardiovascular disease conditions |
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how do you estimate BMR across a variety of species |
1. mass to the power of 0.75 (same relationship w SA means smaller animals have a higher relative BMR) [thermal inertia complex] 2. Harris-Benedict equations F: BMR= 665+ 9.6W+1.8H-4.7Age M: = 66+13.7W+5H+-6.8Age |
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what do the differences between male and female H-B equations tell us |
BMR is directly related to height and weight and inversely proportional to age less variance between women (much higher constant and smaller multipliers) |
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what are factors that effect BMR |
genetics: could be related to thyroid hormone signalling axis age: greater BMR in young ppl partially due to greater percentage lean mass gender: men have a higher BMR partially due to greater lean mass higher exercise/phys act: lifestyle choices can carry over by raising the BMR if theyre especially active but by definition not phys act can occur during BMR measurement thermoregulation (over time): BMR can acclimate to different environments over time but by definition no active treg can be occuring when BMR is measured |
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when will physical activity portion of the NE overtake the BMR portion |
very intensely active individuals |
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variance of BMR between exercise amounts |
sedentary: 1.2BMR extra active: 1.9BMR |
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how much of a role does genetics play in obesity |
little; people from families with high BMR were no more obese than those from families with low BMR |
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what is insensible heat loss |
quantification of heat and water loss through sweat and exhalation, add with sensible heat loss (from direct calorimetry) to yield a total |
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what do direct and indirect calorimetry measure |
direct: change in heat (sensible loss), change in water vapour (insensible) indirect: amount O2 taken in, CO2 expelled, amount of urinary nitrogen produced |
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facts about a direct calorimeter |
expanded version of the lavoisier chamber expensive impractical measures total heat loss has already provided good historical data takes a long time very heavy so must retrofit walls and floors no longer used |
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facts about the indirect calorimeter |
measures O2 consumption and CO2 exhalation in L, [based on the fact that all body processes releasing energy rely on these], urinary nitrogen loss in g simple to set up; no chamber required inexpensive can calculate fuel mixtures (CHO, fat, protein etc) |
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how much protein was oxidized during an indirect calorimetry experiment |
amount N excreted in urine x 6.25 (often ignored bc so small) |
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what is the RQ for pure fat and the RQ for pure CHO |
0.7 and 1.0 |
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how much variance is there between results in the two types of calorimetry |
less than 1% (negligible) |
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what is RQ |
respiratory quotient: L CO2 produced/L O2 consumed reflects gas exchange at a cellular level from nutrient exchange (typicaly ignore that of protein) |
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what are the uses of RQ |
measure energy expenditure proportion of macronutrient used (usually just fat or CHO when urinary N isnt measured) |
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what is significant about the RQ of protein |
right betwwen that of CHO and fats (0.82) so a significant portion would be impossible to distinguish; luckily few experiments involve protein metabolism- one involving lean muscle mass would require urinary protein analysis too) |
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what is unique about the RQ of fats vs CHOs |
CHOs usually arent in any form other than glucose so its basically invariable Fats are in a variety of forms ie fatty acids with different chain lengths so oxidation is varied |
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why is the RQ for fats lower than the RQ for CHO |
much less oxidized substrate, need more O2 to combust relative to CO2 produced |
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at rest the body catabolizes mostly ______ and very little _______ |
fat and very little CHO due to abundance of oxygen in the cells, mitochondria are active, TCA is accepting acetyl coA and feeding reducing equivalents into the TCA for efficient ATP production (CNS and RBC are exceptions; only use glucose) |
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what is the crossover concept |
at rest most energy comes from fat not sugar but during periods of intense exercise CHOs become the primary source of energy which liberates muscle and liver glycogen stores to feel glycolysis ending in lactate formation, can train VO2 max to allow a more sustainable use of fat for energy during activity |
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what does rigorous activity do to the TCA |
NADH builds up and NAD+ decreases inactivating the TCA causing the cell to depends on substrate level phosphorylation in glycolysis so the TCA cant metabolize fats; metabolize glucose to pyruvate for a small amount of energy and the pyruvate is then converted to lactate to restore some NAD+ -- can only be sustained seconds to minutes |