UNIT 3: ENERGY Flashcards
The sum of all chemical reactions involved in obtaining and utilizing food energy is…
Energy metabolism
What does ATP hydrolysis do?
ATP hydrolysis releases energy captured in chemical bonds, driving forward metabolic reactions, and physical movement and releasing heat
What do these have in common?
- physical activity
- anabolic pathways
- active transport
- cell division, growth, reproduction
All are work that require ATP
What is a Calorie?
Calorie: measure of heat, amnt of energy required to raise 1g water by 1 degC
What is the difference between Calorie and calorie?
1 Cal = 1000 cal = 1kcal = 4.18kJ
When a person is in the phases of growth and development, weight gain and obesity, and adults between the age of 20-60… this is what state?
Positive energy balance
dietary energy intake > energy expenditure
What are characteristics of a negative energy balance?
- weight loss and infection
- degrade protein fast to support immune function
- over the age of 60
The measurement of heat production when food sample is completely combusted in high oxygen environments.
Bomb calorimetery
What is heat an indicator of in bomb calorimetry?
Amount of energy stored in chemical bonds of foods (C-H)
Maximum amount of energy that can be obtained when food is completely oxidized metabolically or by chemical combustion.
Gross Energy
What are the 4 steps to bomb calorimetry?
- dry and weigh sample
- prepare bomb (high O2)
- ignite sample
- measure energy (heat released, absorbed by water, change in temp)
What is a major limitation of gross energy?
- measures max amount of energy liberated, therefore…
- does not take into account of energy for physiological work (digestion and absorption)
- human body does not digest and absorb all food energy
What is digestible energy?
Gross energy - energy lost in feces
- energy lost in feces can be determined with % digestibility
Energy is lost from gases and urine (urea - protein). After accounting for this loss, what is this called?
Metabolizable energy.
ME = DE - energy lost in urine/gas
What do Atwater’s Physiological Fuel Values measure?
Metabolizable Energy
(gross energy - feces - gases - urine)
units: kcal/g
What is the ratio for Atwater’s Physiological Fuel Values?
ME (kcal/g)
Fat: 9
Protein: 4
Carb: 4
In fatty acids…
lower GE occurs due to:
- percent of oxidized carbons represents large amount of molecule
- increasing number of double bonds (partially oxidized)
Calories in nutrition fact labels represent ____ energy.
Metabolizable energy
- from Atwater’s Physiological Values
How do you calculate total calories?
Fat x 9kcal/g
Carb x 4kcal/g
Protein x 4kcal/g
Define HIF.
HIF - heat increment of feeding: obligatory energy expenditure for process (energy expenditure while obtaining energy from food)
i.e. chewing, gut secretion, motility, active transport…
How is net energy determined?
Metabolizable Energy (ME) - Heat Increment of Feeding (HIF) = Net Energy (NE)
HIF will be larger for ____ sized meals.
HIF will be larger for ___ macromolecules compared to ____ and ____.
Larger expenditure for larger meals
larger for proteins (15%)
than carbs (10%)
than fats (5%)
Components of energy expenditure include:
- HIF (10%)
- BMR (60% energy expenditure)
- Physical activity (30%)
- Thermoregulation (10%)
What is BMR?
basal metabolic rate
- the measure of energy spent…
- shortly after waking
- post-absorptive state/fasting (avoid HIF expenditure)
- lying down and relaxed - not asleep
- room that is comfortable temperature so there is no energy spent in thermoregulation
Is BMR constant?
- No, it can drop during periods of malnutrition or starvation.
- you can survive on intakes below BMR but tend to be in negative energy balance
What part of the body regulates BMR?
hypothalamus/pituitary/thyroid hormone signalling axis
How do you estimate BMR across species?
Kleiber’s Law
What is Kleiber’s Law?
- metabolic rate varies with body weight by 0.75 exponent
Metabolic Rate (is proportional to) Mass^0.75 - note* this is not applicable to humans
A ____ surface area to body weight ratio would conserve energy and lower energy expenditure.
lower
i.e. elephant
What are the equations used to calculate BMR for humans called?
Harris-Benedict Equations
Metabolic rate is ____ variable in women than men
Less variable
- higher constant in female (665)
- male constant (66)
What are 5 factors that affect BMR?
- genetics
- age
- gender
- higher exercise/physical activity
- temperature
Age: ____ people have higher BMR
young people
because greater % lean mass
Gender: ____ people have higher BMR
men
because greater % lean mass
Temperature ____ increase BMR
higher thermoregulation
*note thermoregulation cannot occur during BMR measurement
Bomb calorimetry is direct or indirect calorimetry
Direct calorimetry
- assess potential energy
How is energy expenditure measured?
indirect or direct calorimetry
Humans and animals are used for what type of calorimetry?
Direct calorimetry
How is energy measured in direct calorimetry?
- emitted heat absorbed by water/walls (measure change in heat) = sensible heat
- account of sweat and vapour in expired air (measure change in water vapour) = insensible heat loss
What is the main difference between what indirect vs direct calorimetry measures?
Indirect: O2 and CO2
Direct: H2O and heat
What is the purpose of measuring O2 and CO2 in indirect calorimetry?
to indirectly measure the H2O and heat produced from combustion
What needs to be estimated in order to accurately estimate energy expenditure in indirect calorimetry?
- what fuels are being utilized!
What sample is needed in order to calculate protein oxidized in indirect calorimetry?
- urine sample to calculate urinary nitrogen
- this quantifies oxidized protein
What is RQ?
Respiratory Quotient
- volumes of oxygen consumed and volumes of carbon dioxide measured from indirect calorimetry
Formula for RQ
RQ = (CO2 produced (L)) / (O2 consumed (L))
Match the RQ values to their macromolecules:
0.7, 0.82, 1.0
Carbs 1.0
Protein 0.82
Fat 0.7
- in calorimetry experiments protein loss is uncommon, but if protein is lost (loss of lean body mass) then urinary nitrogen would need to be measured
Given volume of O2 consumed and CO2 produced, how do you find calories produced.
- find RQ (CO2produced / O2consumed)
- find caloric equivalent
- multiply caloric equivalent by L produced or consumed
- this gives you calories produced per time of measurement
