4: Review of nutrients 2 Flashcards
What is energy? What requires it?
the ability to do work (all activities of the body require it)
Not a nutrient, it is derived from macronutrients (fats, CHOs, proteins)
How is energy derived from macronutrients
CHO: glycolysis (breakdown of glucose makes CO2 and chemical energy)
Excess amino acids deaminated and oxidized to create energy
What happens to the components of aa after deamination (N and carbon skeleton)
To use as energy, N must be seperated from the carbon skeleton through deamination in the liver
Two N molecules, combined into urea, are excreted by the kidneys via urine
Certain C skeletons can be converted back into glucose (glucogenic), others used in fat metabolism (acetogenic), some do both
How do we determine the gross energy content of food
Calorimetry
- bomb calorimeter
- burning of food
- measurement of amount of heat released
Unit of measurement for energy
Joule or calorie
1 kcal = 4.184 kJ
1 calorie is the amount of energy required to increase the temperature of 1 g of water by 1C
Slides 5, 7
KNOW 7 BY HEARTTT
What is heat increment
Energy released in form of heat after meal. Storing energy requires energy which is lost in the form of heat.
*Energy needed for digestion, absorption and metabolism of food
What is metabolizable energy? Digestible energy?
ME = energy not excreted in fecal material or urine
DE = amount of energy that enters the body through the enterocyte
Advantages and disadvantages of a net energy system
Advantages:
- more precise than ME & DE
- actual energy amount that is available to the body from digestion and metabolism of feed
- efficiency of energy utilization
Disadvantages:
- more experimental data needed
- heat loss must be measured
What is basal metabolic rate BMR
The energy requirement for a normal animal (not reproducing, growing, etc) in a thermoneutral environment, awake but without movement (resting) and in a postabsorptive (fasting) state
What is resting fed metabolic rate (RFMR)
The energy requirement for a normal but unfasted (fed) animal at rest in a thermoneutral environment.
Includes energy needed for digestion, absorption and metabolism of food (heat increment)
What is maintenance energy requirement (MER)
The energy requirement of a moderately active adult animal in a thermoneutral environment
Includes energy needed for obtaining, digesting and absorbing food in amounts to maintain body weight and energy for spontaneous activity
MER does not include energy needed to support additional activity (work, gestation, lactation and growth) (would calculate kcal/day over MER)
Describe water as a nutrient. Sources?
Most important nutrient, largest body constituent (varying from 40 to 80%)
sources:
- fresh (drinking) water
- water in the food
- metabolism
How is water produced in metabolism
Glucose + O2 -> CO2 + H2O
What are the five forms of water loss
- urine (largest loss = 75-85%)
- feces (2nd largest)
- respiration (breathing = water vapor lost from the lungs in exhaled air)
- sweat (not usually large in companion animals)
- milk (85-90% water) during lactation
Four main functions of water
- solvent to dissolve and transport substances
- necessary for chemical reactions that involve hydrolysis (enzymatic digestion of CHOs, fats, protein)
- regulation of body temperature (evaporative cooling)
- provides shape and resilience to body (lubricates joints, eyes)
Examples of water as a solvent to dissolve and transport substances
- ion balance across cellular membranes
- transport of nutrients within and among cells
- elimination of waste products through urine
What systems regulate the amount of water in the body
Neural and endocrine
