Energy Flashcards
What is energy used for?
Growth, movement, bodily functions (keeping warm, breathing etc.)
What is the 1st law of thermodynamics?
Energy cannot be destroyed or created
What are the Atwater factors for Carbohydrate, Protein, Fat and Alcohol?
C- 3.75/4
P- 4
F- 9
A- 7
How would we work out the metabolisable energy?
Ingested (gross) energy - energy in urine and faeces
Or…
Using Atwater factors
What is the basal metabolic rate (BMR) and how many kilocalories does it use per minute?
The minimum amount of energy needed to keep someone alive at rest
0.9-1.5kcal/min
What processes are included in basal metabolism?
Cell function and replacement Synthesis, secretion and metabolism of enzymes, hormones and other substances Maintenance of body temperature Cardiac and respiratory muscle function Brain function
What factors determine a persons BMR?
Fat free mass* Body mass Gender Age Height Body composition Genetic variation
How would we measure BMR?
Using calorimetry
Direct- measuring heat loss
Indirect- measuring heat production by assessing oxygen consumption and carbon dioxide produced
Give an example of direct calorimetry and explain its process
Lavoisier’s calorimeter
Heat from guinea pig melts the ice in the inner jacket. The melted ice is collected and weighed. Ice cavity is surrounded by a space filled with snow to maintain a constant temperature.
Whole body calorimeter
Measures heat loss for overall energy expenditure. Enclosed respiration chamber (airtight), controlled temperature, computer monitors samples of gas inside chamber.
Give an example of indirect calorimetry and briefly explain how it is carried out
Douglas bag
Collect expired air into a bag, O and C are analysed in a sample and the volume of air is measured to calculate EE.
Kofrani-Michaelis respirometer/ oxylog
Measures expired air composition and volume as it is collected. No need to collect gas.
Ventilated hoods
Open canopy with air in/ air out controlled. Continuous monitoring of O consumption, C production and respiratory quotient (RQ).
Hand-held calorimeter
Measures O consumption and analyses O in expired and inspired air and volume is detected. Does not measure C and assumes a RQ of 0.85.
What is the RESPIRATORY QUOTIENT and how would you measure it?
The RQ is an indication of the proportion of energy expenditure derived from fat and carbohydrate oxidation i.e. a RQ of 1.0 would represent pure carbohydrate oxidation.
CO2 produced/O2 consumed
What value of RQ would represent a mixed diet?
0.85
Give some examples of thermogenesis
Diet-induced Drug and alcohol-induced Cold-induced Psychological Muscular
Give some examples of how physical activity can be measured
Heart rate monitoring Accelerometers GPS Questionnaires Doubly labelled water
How does doubly labelled water work?
Water is labelled with stable isotopes 18O and 2H (deuterium). 18O is eliminated as C and W, 2H only as W. By measuring the difference between the elimination rates of the isotopes, C production rate can be calculated. This is converted into energy expenditure by knowing the respiratory quotient of food ingested in the observation period
