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
