Lecture 4

Question 1

What is ATP?

Answer 1

• cellular source of energy
• supplied by macronutrients in the diet
• sustains physical energy, metabolism, active transport, etc.

Question 2

What is a Calorie?

Answer 2

measure of heat to express the energy content of food

Question 3

What is the conversion of a chemistry calorie vs a food calorie?

Answer 3

1000 chemistry calries = 1 food Calorie

Question 4

What is the difference between calorie and Calorie?

Answer 4

calorie = chemistry
Calorie = food

Question 5

What is the conversion of food Calorie to kcal to KJ?

Answer 5

1 food Calorie = 1 kcal = 4.18 KJ

Question 6

What is the method used to estimate energy in foods?

Answer 6

Calorimetry = measurement of heat production

Question 7

What is calorimetry?

Answer 7

Uses heat as an indicator of the amount fo energy stored in the chemical bonds of foods (carbon-hydrogen bonds), when these bonds are broken down, they release heat

Question 8

What is bomb calorimetry?

Answer 8

works according to the principles of direct calorimetry (directly measures the amount of energy stored in chemical bonds of foods)

Question 9

What are the steps to bomb calorimetry?

Answer 9

1. dry and weigh sample (1g) and place in enclosed chamber (the bomb) with oxygen
2. The sample is ignited
3. heat that is released is absorbed by water and measured

Question 10

What is the heat of combustion equal to?

Answer 10

Heat of combustion (gross energy) = maximum energy during a chemical reaction

Question 11

What are the potential errors of bomb calorimetry?

Answer 11

• overestimates energy (we don’t digest food like a bomb calorimeter burns it)
• doesn’t take into account the energy needed for digestion and absorption

Question 12

What are the physiological fuel values? (Atwater values)

Answer 12

CHO = 4
Fat = 9
Protein = 4

Question 13

What is the formula for the physiological fuel values?

Answer 13

[Heat of combustion(gross energy) - energy lost in urine] x apparent digestibility
(a-b) x c

Question 14

What are the units of the factors in the formula for physiological fuel values?

Answer 14

Heat of combustion(gross energy) = kcal/g
Energy lost in urine = kcal/g
Apparent digestibility = %

Question 15

What are two other names for physiological fuel values?

Answer 15

available energy
metabolizable energy

Question 16

Why does fat provide more kcal/g vs CHO or protein?

Answer 16

The heat of combustion (kcal/g) describes the total energy released during a chemical reaction between a hydrocarbon and oxygen to release CO2 and H2O and heat. The chemical structure of CHO, fat and protein influences the heat of combustion for macronutrients
CHO - ratio of hydrogen to oxygen = 2:1
Protein - has nitrogen which affects gross energy measurement, however in the body, nitrogen combines with hydrogen and is eliminated as urea. This loss of hydrogen affects the heat of combustion
Lipid - lipids are less oxidized than CHO and protein, ratio of hydrogen to oxygen is much greater than 2:1, lipids have lots of hydrogen atoms available for cleavage oxidation for energy

Question 17

What is stearic acid?

Answer 17

used for meat, poultry, fish, milk products, grains

Question 18

What is butyric acid?

Answer 18

• SCFA
• produced by gut bacteria

Question 19

What are the two factors that affect the heat of combustion of fatty acids?

Answer 19

• chain length: longer chain length releases more energy
• degree of unsaturation: the more double bonds, the less energy released (for equivalent chain length fatty acids)

Question 20

How to use the atwater values in a practical sense?

Answer 20

Can multiply the grams of the nutrient on the nutrition label by the atwater value for that nutrient and get the kcal

Question 21

What is heat increment of feeding?

Answer 21

(HIF)
- also called thermic effect of food
- energy used for the digestion, absorption, distribution and storage of nutrients
- comprises 5-30% of daily energy usage
- used to determine net energy

Question 22

What is the formula for net energy

Answer 22

Net energy = matabolizable energy - HIF

Question 23

What is net energy?

Answer 23

Supports basal metabolism, physical activity, growth, pregnancy

Question 24

What are the four components to energy expenditure?

Answer 24

1. basal metabolic rate (BMR) - main driving force, basic energy needs, resp blood flow etc.
2. Thermic effect of food (same thing as HIF) - absorption, metabolism of food
3. Physical activity energy expenditure (PAEE) - varies from person to person, energy spent using voluntary muscles
4. thermoregulation (energy spent maintaining body temp)

Question 25

How is BMR measured?

Answer 25

- shortly after waking - done in a lab - come to lab before and sleep - post-absorptive state - lying down - completely relazed - comfortable room temperature - BMR = kcal per 24 hrs

Question 26

What tissues are most reflective of the BMR?

Answer 26

Muscle and bone

Question 27

What is the formula for BMR?

Answer 27

BMR = A x [M^0.75] kcal/day A = metabolically active tissue (fat free mass, muscle and bone), the value for humans is 70 M = body weight in kg 0.75 = constant used for all vertebrates, invertebrates and even unicellular organisms

Question 28

What are factors that can affect BMR?

Answer 28

- Genetics (inheritance of a fast or slow metabolic rate) - Age (young>old because of greater muscle mass) - Biological sex (men>women because of greater muscle mass) - Exercise changes body tissue proportions fat tissue (20% BW, 5% metabolic activity) muscle (30-40% BW, 25% metabolic activity) brain, liver, heart and kidney (5% BW, 60% metabolic activity) - temperature (maintaining thermoregulation

Question 29

Can you use body fat % to calculate BMR?

Answer 29

if you measure body fat %, you can have a more accurate measure of BMR

Question 30

Heat production can be used as a measure of ___________

Answer 30

energy expenditure

Question 31

What is the general combustion equation for indirect calorimetry?

Answer 31

Fuel + O2 ->(resp) CO2 + H2O + heat Fuel - diet (CHO, protein, fat) heat - direct cal O2 and CO2 - indirect cal

Question 32

What is direct calorimetry?

Answer 32

Measures the heat a person generates; total heat loss, spend 24h in the chamber, very expensive and impractical

Question 33

What is indirect calorimetry?

Answer 33

energy releasing reactions in the body depending on the use of oxygen

Question 34

What does indirect calorimetry measure in order to estimate energy requirements?

Answer 34

- oxygen consumption (L) - carbon dioxide production (L) - urinary nitrogen loss (g)

Question 35

What can indirect calorimetry not account for?

Answer 35

anaerobic processes

Question 36

What are the advantages and disadvantages of indirect calorimetry?

Answer 36

Disadvantages: hyperventilation, hard to get an airtight seal, masks are impractical, could give flawed measurements Advantages: useful with animals, can determine the type of substrate being oxidized

Question 37

What is the respiratory quotient?

Answer 37

- provides information about energy expenditure and biological substrate being oxidized - ratio of metabolic gas exchange

Question 38

What is the formula for the respiratory quotient?

Answer 38

RQ = CO2 produced/O2 consumed

Question 39

What nutrients are the main contribution of RQ?

Answer 39

assume CHO and fat

Question 40

Why does RQ vary for macronutrients?

Answer 40

Differences in chemical composition mean that each macronutrient requires a different amount of oxygen intake in relation to CO2 produced

Question 41

How to use the table to calculate RQ?

Answer 41

For each non-protein RQ value there is a caloric value for each L of O2 consumed or CO2 produced, table tells you how much CHO and fat contribute to energy