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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)







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)



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

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

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



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

what are dietary fats used for

make membranes, storage triglycerides, cholesterols etc



what are dietary carbs used for

storage glycogen, glycoprotein and glycolipids which will all be oxidized to make energy

what are dietary proteins used for

source of aa to make own protein and enzymes

Calories on a nutrition label refers to what

metaboloizable energy

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)

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

who recognized that proteins, fats and carbs are oxidized in the body

von leibig

who measured energy values

rubner

what did atwater do

studied disgestion and defined metabolizeable energy that we will use today

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

what are the products of food oxidation

CO2, H2O, heat

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

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

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

where does metabolizeable energy come from

oxidation via glycolysis and the TCA

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

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

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

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

what type of calorimtery do bomb calorimeters provide

direct: provides gross energy

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

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

at what stages are feces, urine and gasses lost in metabolism

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

what are atwater physiological values used for

multiply by the grams of macronutrients to get ME for that macro

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

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

what are the atwater values

P: 4 (due to excretions)


CHO: 4


F: 9

rank the macronutrients from most to least digestable

CHO is more digestable than fat which is more digestable than protein

how to arrive at ME

multiply GE (value from direct calorimetry) by percent digestability and arrive at the ME

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

methanol and CHOs have _______ inherent oxidation

some (arent fully saturated)

rank the macronutrients from most to least oxidized

fats then proteins then CHO, so less oxidation is available= less energy available

where is a fully oxidized C on an FA

carboxyllic end

why is the stearic acid GE similiar to the atwater value for it

it is a common dietary fat

what is the effect of longer chains on FA oxidation

lower oxygen ratio making higher energy potential

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

what is the most consistent atwater fraction

CHO

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

why do companies ask to remove the amount of insoluble fibre from the total energy expenditure

to seem more attractive to consumers



what do Calories reflect on the nutrition label

atwater physiological values- total of (9xg fat)+(4xgprotein)+(4xgCHO)

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

what is the net energy equuation

ME-HIF=NE

what is HIF

heat increment feeding; obligatory energy expenditure

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

what is the NE

supports basal metabolism, pregnancy and growth etc)

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

what is the avg BMR for an adult

1800kcal/day (75/hr)

when does energy expenditure peak

about two hours after a meal, then goes back to baseline BMR

what is the graphic interpretation of energy expenditure

area under curve but above the resting BMR line

what is another term for HIF

thermic effect of food

what are the four components of energy expenditure

HIF


Basal metabolism


physical energy expenditure


thermoregulation

which has the highest use the NE after subtracting for HIF (~10%)

BMR takes up about 60% then phys. (30%) and thermoreg (10%)

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

how can physical activity and individual characteristics affect BMR

professional atheltes and other very physical people may have higher BMR


-sedentary modern lifestyle



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

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



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)

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

when will physical activity portion of the NE overtake the BMR portion

very intensely active individuals

variance of BMR between exercise amounts

sedentary: 1.2BMR


extra active: 1.9BMR

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

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

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



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

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)

how much protein was oxidized during an indirect calorimetry experiment

amount N excreted in urine x 6.25 (often ignored bc so small)

what is the RQ for pure fat and the RQ for pure CHO

0.7 and 1.0

how much variance is there between results in the two types of calorimetry

less than 1% (negligible)

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)

what are the uses of RQ

measure energy expenditure


proportion of macronutrient used (usually just fat or CHO when urinary N isnt measured)



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)

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

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

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)

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

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