Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
62 Cards in this Set
- Front
- Back
|
international unit of energy |
Joule |
|
|
Definition of unit of international unit of energy |
amount of energy used when a mass of 1kg is moved by a force of 1 newton |
|
|
units of energy expenditure when expressed in units of time |
e.g. KJ/MIN Watts= J/s or KJ/s |
|
|
definition of a calorie |
heat necessary to raise temperature of 1cm3 i.e. 1g of water by 1 degree centigrade |
|
|
interconversion numbers 1) how many KJ in 1 Kcal 2) how many Kcal in 1 KJ |
1) 4.2 KJ 2)0.24 kcal |
|
|
what is heat of combustion and how is measured what units are used? |
1)energy liberated by oxidation of food/ gross energy within food, measured by bomb calorimetry 2) energy measure in this was= GE kj/g |
|
|
Gross energy of major nutrients (highest to lowest) |
fats alcohols protein starch glucose |
|
|
For what two reasons are not all energy available to the body? |
1) not all food absorbed from digestive tract i.e. digestible energy (99% carbs, 95% fats and 92% protein) 2) not all energy is protein is released nitrogen converted to urea which is excreted in urine, this accounts for 1/4 of chemical energy in protein (5.2kj/g) |
|
|
what is metabolisable energy? |
proportion of energy available to the body after urine and faeces loss from gross energy, measured directly using mutplie samples |
|
|
What is the order of metabolisable energy contents of major nutrients and what is the values? |
fat 37.1 (kj/g) starch 17.3 protein 15.9 glucose 15.4 alcohol trace |
|
|
What are the ME assumptions? |
1) animal and vegetable proteins have different ME values- we use averages 2) Fats have different ME dendign on the length of FA chain- we use average values 3) digestible energy is the same for all fats and proteins 4) assume fibre DOESN'T contribute to ME 5) assume person is healthy and doesn't have any metabolic condition which would affect absorption |
|
|
How to calculate ME content of food? |
multiply amount by ME value for each nutrient component sum of these values= ME content of feed |
|
|
Why is there is there differences between values on packet and value calculated? |
1) manufacturers use ATwater factors but have not accounted for urinary and nitrogen losses 2) doesn't distinguish between starch and glucose 3) doesn't have energy contributed from starch |
|
|
problems with ME/ ME assumptions |
1) assume all protein, carbs and fats contribute same ME 2) some forms of starch are indigestible or only when cooked 3) assume 6.25g of protein contsains 1g of N (not always true) 4) different FA have different digestibility's (NOT TRUE (unsat>sat) -saturates differ mystiric> palmitic>stearic |
|
|
Components of energy expenditure and % of that exepnditure |
1) basal metabolic rate 60% 2) physical activity rate 30% 3) thermal effect of food 5-10% -diet induced thermogenesis/post prandial thermogenesis |
|
|
Three methods of measuring energy expenditure and how they measure energy expenditure |
1) direct calorimetry- measures body heat 2) indirect- measures 02/c02 consumption at rest 3) non-calorimetric methods e.g. RER |
|
|
Direct calorimeter (measures heat in live in chambers) -what is lavoisier's method, what energy expenditure does it measure and how? -atwater rosa calorimeter |
1) animal in ice surrounded chamber, measures water melted, determines basal metabolic rate by determining how much heat given off by its body temp by measuring volume of melted water 2) live in chamber, water pumped through and change in temp= energy given off by individual, insulated chamber, ventilation- air continually passes across scrubbers that remove moisture and c02 (h2so4= water and soda lime= c02) |
|
|
Disadvantages of direct calorimetry |
1) difficult as corrections required for all heat entering and leaving the chamber 2) has to be made over long periods of time as it is assumed that there is NO net change in body temp 3) not applicable for determining energy expenditure for most sports of occupational activities |
|
|
Indirect calorimetry and principles |
-all feed product entering body oxidised to same end products i.e. c02, h20 and urea -almost no other loss of products i.e. macronutrients are virtually completely oxidised -method of estimating energy expenditure by measuring respiratory gases i.e. 02 consumption and c02 production |
|
|
Calculating energy from one mole of glucose |
1) look at amount of heat produced 2) look at amount of glucose 3) divide heat by amount---- Kj/g |
|
|
calculating energy produced by L 0f oxygen |
1) look at amount of heat produced 2) find out how many L of 02 consumed e.g. mole x number of L 3) divide energy by no. of L------ KJ/L |
|
|
Work out how much energy produced by substrate? |
multiply amount used by energy released by the substrate during oxidation of different substrates |
|
|
What does o2 consumption provide? |
gives an approximation of energy expenditure -while amount of energy produced per gram of substrate varies energy produced per L of 02 is similar |
|
|
What is mean KJ value produced by 02 during oxidation of nutrient? |
20.1KJ/L |
|
|
how can amount of energy expended be calculated using IC? |
ratio of c02 produced/ 02 consumption |
|
|
What is respiratory quotient ? What level is this measurement at> |
measurement at cellular level RQ= Vc02 * no of L/amount of substrate ----------------------------------------------------- V02 * no.L/ amount of substrate |
|
|
what is respiratory exchange ratio and what level is it measured at? |
RER= Vc02 --------- V02 -ratio of c02/02 on oxidation of nutrient measure from expired air -RER of Glucose= 1 |
|
|
To determine RQ values |
1) no of L x moles divided by weight of nutrient do this for both oxygen and carbon dioxide |
|
|
What does RER values relate to? |
relates to amount of carb/fat used - look at table and shows % of cabr/fat use |
|
|
What equation would you use of more accurate values or if you want to know more about which substrates are used? what other parameter do you need to know? |
Energy expenditure -need to know about c02 production and nitrogen excretion in urine |
|
|
What is the equation for energy expenditure? |
16.48v02 (l) + 4.628V02 (l) - 9.079N (g) |
|
|
What are examples of three methods of closed circuit calorimetry? |
1) haldene- animal in closed box 2) modern closed circuit small animal calorimeter 3) closed circuit spirometer |
|
|
How does closed circuit spirometry measure enegery expenditure and what are the advantages? |
-sealed system with c02/h20 absorbed by scrubbers -used in space craft/submarine -simple cheap apparatus |
|
|
Is closed circuit spirometry indirect of direct calorimetry? |
indirect |
|
|
Haldene method |
-animal in closed box -c02 and h20 removed from air in/air out -c02 and h20 estimated by weighing animal's container and h20/c02 scrubbers at start and end |
|
|
Modern closed circuit small animal calorimeter |
-8 channel -external soda lime (c02) and silica (H20) gel absorbing cartridges -water jacketed chambers -peristaltic pumps feed 02 and maintain constant pressure -RER tricky to measure |
|
|
Closed circuit spirometer |
-subject inhales 100% 02 from a pre-filled chamber (spirometer) -expired air goes back to container via soda lime which absorbs c02 -kymograph spins at known speed and records 02 uptake from changes in systems volume (water level) |
|
|
Human rate of energy production |
humans release approximately 20.18 KJ of available energy for every dm3 of 02 consumed |
|
|
disadvantages of closed circuit spirometry |
-tricky to measure RER -can monitor for minimal time modem animal c- no access to food and water spirometry- subject remains close to bulky machinery and limited time (depends on V02) |
|
|
What are examples of open circuit calorimetry methods? |
1) modern open circuit indirect calorimeter 2) open circuit spirometry -douglas bag -portable spirometry -Computerised instrument (resting metabolic canopy) -doubly labelled water |
|
|
Open circuit calorimetry how it works? |
-air passed through chamber at a constant flow -difference in gas composition measured -complex/expensive apparatus and complex calculations -more versatile (scrubbers have limited lit) |
|
|
Modern open circuit indirect calorimeter |
-c02 and 02 (hence RER) determined form knowing flow rate and difference in gas composition before and after measuring chamber |
|
|
Open circuit spirometry |
-Subject inhales ambient air with constant composition of 20.93% 02, 0.03% c02 and 79.04% N -differences in inhaled/exhaled air composition shows metabolism - analysis of Vin/Vout provides useful way to infer energy expenditure |
|
|
Douglas bag |
-subject breaths through valve which separates expire and inspired air -all expired air is directed to non-permeable bag -02 inhlaed/c02 exhaled measured therefore consumption/production calculated |
|
|
Resting metabolic canopy |
-participants lay supine at complete rest under hood or canopy -02 inhaled and c02 content of expired air is measured therefore RER and RMR can be determined |
|
|
Non-calorimetric method: free living conditions method |
isotope dilution method- doubly labelled water |
|
|
Doubly labelled water method |
1) subject given dose of known volume of water labelled with isotopes (2H2180) 2) isotopes diffuse through body's water and their disappearance rate from bodily fluid measured 18O decreases measured for H20/CO2 output 2H2 decrease measure of H20 output alone C02= V18O-V2H2 |
|
|
How is energy expenditure calculated ? |
-c02 production rate converted into energy expenditure by knowing RER of food ingested during observation period -rate of c02 production is to estimate energy expenditure over the period in which body water samples are collected -equation uses measure values for RER and urinary nitrogen production (equation in notes) |
|
|
Advantages of DL water |
-can be used in a wide range of situation including babies, pregnant women, hospital patients and animals living in the wild -gives closest measurement of free living expenditure |
|
|
Disadvantages of DL water |
-expensive isotopes and analysis (mass spec) - affected by fuel burnt (02 not measured) -expertise needed in determining amounts using mass spec |
|
|
What are the components of energy expenditure? |
1) Basal metabolic rate (70%) of expenditure 2) Physical activity Rate (20-40%) 3) Dietary induced Thermogenesis (5-10%) |
|
|
What is Basal metabolic rate? What is energy in BMR used for? What organs contribute most to BMR? |
amount of energy expended while at rest in a neutrally temperate environment in post absorptive state -energy in this state only sufficient for functioning of vital organs -muscle greatest contributor, liver, then brain, than all the rest |
|
|
What affects BMR? |
1) Body size- accounts for half the variability in BMR in human adults 2) Body composition- adipose tissue has lower metabolic rate than lean adipose tissue 3) Age- in adults BMR tends to decline with age as lean tissue is lost and adipose tissue is gained 4) Sex- differences in body size and composition result in differences between sexes |
|
|
Calculation for BMR |
Q (MJ/d)= 0.295 x W (to power of 0.75) |
|
|
What is relationship between body size and BMR? |
-in mature animals direct relationship between body size and BMR -bigger animals produce more heat at basal conditions -but tissue of smaller animals tend to have higher metabolic rates i.e. higher Mass lower BMR |
|
|
What is Physical activity? |
-20-40% of energy expenditure -associated with muscular exercise -highly variable between animals (working dogs vs pet) -highly variable within animals (intense day vs rest) |
|
|
How is physical activity periods divided and what are the values normally for? a) sedentary animals b) active animals |
-24 hr energy expenditure marker by period of resting energy expenditure a) >1.5 b)<2.0 |
|
|
What is dietary induced thermogenesis and what % of energy expenditure does it account for? |
-ingestion, digestion and assimilation of food requires energy and increases heat production -accounts for 5-10% energy expenditure |
|
|
How to calculate DIT? |
DIT= RFMR-BMR -resting fed metabolic ratio> BMR -DIT NOT considered useful to animal except at low ambient temps------contribute to maintenance of body T |
|
|
What does DIT involve? |
-digestion (enzyme secretion, nutrient and transport) -forming tissue reserves of fat, glycogen and protein -uses 5-10% of meals total energy |
|
|
What are the two phases of DIT? |
1) CEPHALIC PHASE -increase in metabolic rate due to taste and smell of food -occurs every time meal is provided irrespective of size 2) POST-ABSORPTIVE STATE: -increase in temp is of low magnitude but long lasting -lasts up to 6-11 hrs after meal -dependent on meal size |
|
|
What energy is required for digestion of: 1) PROTEINS 2)CARBS 3)FAT |
1) difficult digestion (30% of energy consumed get burnt) 2) complex starch (13%) Vs Simple Starch (3%) 3) readily absorbed 3% |
