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44 Cards in this Set

  • Front
  • Back
capacity to do work
sum of all chemical transformations that occur in the cell/organism

occurs in series of enzyme catalyzed reactions that constitute metabolic pathways
synthesis of lipids, polysaccharides, proteins, and nucleic acids

endergonic- require input of energy from hydrolysis of ATP and reducing power of NADPH and NADH

amino acids, sugars ,fatty acids, butrogenous bases--->proteins, polysaccharides, lipids, nucleic acids

break down to lactic acid, CO2, NH3)

Exergonic- release of free energy that is turned into ATP and reduced electron carriers (NADH, NADPH)

Carbohydrates, fats, proteins---> CO2, H2O, NH3

ATP (adenosine triphosphate)
most important

carries chemical energy between metabolic pathways by serving as a shared intermediate coupling endergonic and exergonic reactions
NADP (nicotinamide adenine dinucleotide phosphate)
coenzymes functioning as carriers of hydrogens and electrons in same oxidation- reduction reactions

contains nicotinamide
FAD (flavin adenine dinucleotide)
coenzyme of some oxidation- reduction reactions

contains riboflavin
Energy Balance
amount of nutrient consumed sufficient to maintain weight
Forms of Energy
chemical- photosynthesis

mechanical- muscle movement
photosynthetic bacteria and higher plants

Use CO2 from atmosphere as source of carbon from which they construct all carbon-containing compounds (sugars)
Photo- Autotrophs
depend on light to construct carbon containing biomolecules
must obtain carbon from environment in form of complex organic molecules
Importance of energy in animal metabolism
1. required in larger amount than any other nutrient

2. most often limiting factor in livestock production

3. major cost associated with feeding animals

*animal NOT EFFICIENT at transforming feed energy into its own body energy
Methods of measuring energy value of feedstuff
1. Total digestible energy

2. starch equivalent

3. caloric system (current system)
Total Digestible Nutrient System (TDN)

Computation of digestible nutrients:

[Digestible protein(protein+fiber+nitrogen free extract)+(fatx2.25)]

*multiply fat by 2.25 because there is 2.25 times more energy in fat than carbs.

*digestible protein= protein consumed-protein in feces

TDN usually expressed as percent of ration/units of weight
Advantage of TDN System
used for a long time and many people are used to this system
Disadvantages to TDN System
TDN is a misnomer (not actual value of TDN)

does not include minerals

based upon chemical determinations and not related to actual metabolism of animal

expressed as weight/% whereas energy expressed in calories

considers only digestive losses and does not take into account losses in urine, gasses, and increased heat production
Feed Energy in Animal Systems
true digestibility difficult to measure because undigested residues and urinary wastes are excreted together

convenient to determine metbolizable energy of a diet by pooling excreta as a single material representing unutilized portion of the feed energy
Energy Partition Scheme: Pigs
DE system preferred because:
easy to measure

gaseous products from pigs considered to be insignificant and are ignored

Energy Partition scheme: Ruminants
ME System:
considers gaseous lost

NE System (preferred):
animal requirements stated as net energy are independent of the diet

feed requirement for maintenance are separate from feed needed for productive functions
Partition of ME in the Growing Animal
some species more efficient than others

some individual within species more efficient than others

as we age, out metabolism slows and we gain more fat

optimum stage for slaughter: when animal is most lean- before too much fat accumulates
Basal metabolim
heat production from a healthy animal achieved when it is not given feed for some time and is kept in a thermoneutral environmet with a minimum of activity
Maintenance Metabolism
fed animal in stable weight and chemical composition over a period of time

Maintenance heat production is always HIGHER than basal metabolism because of the process of eating and digesting and metabolizing feed requires energy produced as heat
Contributers to heat production
1. factors relating to the processing of the diet by the animal:

work done in location (ex. animal goes to hunt), prehension, and mastication of food

work done by movement of digestive tract

heat of fermentation of certain dietary constituents

heat increment associated with metabolic processing of nutrients

2. Factors associated with non food related ativities:

maintain body temp.

work of circulation, respiration, maintenance of posture, standing, and locomotion

energy cost of basic metabolic processes, including tissue turnover
Direct Calorimetry
animal confined in well-insulated chamber and heat losses by:

radiation, convection, and conduction from body surface

evaporation of water from skin and lungs

evaproation of water and feces by increase in temp. in known volume of water and electrical current generated as heat passes across thermocouples

Most accurate method of measuring heat production of animals, but EXPENSIVE
Indirect Calorimetry
heat production calculated from measurement of respiratory exchange:
O2 consumption, CO2 production

Respiratory Quotient= CO2 produced/O2 consumed
Starch Equivalent
Expressed energy values of feeds relative to net energy value of common feed constituent, starch

SE= energy value of feed/energy value of starch
Units of Energy
Calorie: units of heat used to describe energy yielding capability of foods on complete combustion
Calorie= amount of heat required to raise 1g pure water 1C.

1calorie=4.184 Joules
Caloric System
Gross Energy (GE)- total energy in feedstuff

Digestible Energy (DE)= total energy in feed-energy in feces

Metabolizable Energy (ME)

Net Energy (NE)= used for maintenance and growth
NEm (energy used for maintenance only)
NEp (energy used for production only)
Gross Energy (GE) of Feed
heat henerated when a unit mass of feed is completely combusted in oxygen to yield carbon dioxide and water under standard conditions of temp. and pressure.

heat combustion measured by combustion calorimeter
Digestible Energy (DE)
GE of feed consumed- GE of feces

DE values of no use in avian because uric acid is all together
Metabolizable Energy (ME)
GE-fecal E-Urinary E-Gaseous products

Most common method used for poultry
Net Energy (NE)
ME+heat increment+ NEm+ NEp

Very accurate measure of E value of feed

Difficult to determine
Heat Increment of Feed
Heat released through body:
- muscle contraction
- digestion of food and metabolism of nutrients derrived from them

*act of chewing= ~3-6% ME intake
3.Metabolism of gut microflora in ruminents (7-8% ME intake)
4.Secretion of Saliva
1. Endergonic: energy must be added, can end up with more energy

2. Exergonic: give off energy

*both types of reactions often occur together (coupled)
1. chemical conversion of feedstuff into biological E

2. this conversion sustains life

3. Conversion occurs within cells
First law of Thermodynamics
total energy in universe remains constant, but may change form
Sources of energy
1. Carbohydrates: C,H,O

2. Fats: a lot of C&H, some O

3. Proteins: C,H,O,N,S
1.Monosaccharides: glucose, fructose

2.Disaccharides: sucrose (glucose&fructose), Maltose (glucose & glucose)

3. Polysaccharides: plant or animal source, glycogen mose common

*brain depends only on glucose for survival
1g=9kcal of energy

insoluble in water

4 Groups:
fatty acids- stored as triglycerides in adipose tissue

triglycerides- 3 fatty acids and glycerol

phospholipids- structure, insulation of nerves

steroids- cholestrol and hormones
1g= 4kcal

made up of 20 amino acids

9 amino acids are essental

must be broken down to amio acids then used for energy

easily converted to glucose
Bio-Energetic Pathway
1. Anerobic- glycolysis

2. Aerobic- glycolysis, TCA/Kreb cycle, electron transport system
adenosine, ribose, and phosphates

may form from AMP or ADP

breakage of phosphate bonds by ATPase releases energy
1. Glycolysis:
2 NADH formed
electron carriers
lactic acid
*cyanide stops electron transport chain instantly