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Metabolism
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Covers the basics of metabolism, along with different types of metabolism and how it can be affected.
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Comparative Anatomy and Physiology in AnimalsLecture 7 Metabolism 03/11/20
Metabolism in animals
- Metabolism is the sum of processes by which animals acquire energy, channel energy into
useful functions, and dissipate energy from their bodies
- Animals are organised or order systems of cells, tissues and organs that function in
combination to allow the organism to survive
- Feeding and digestion provide essential nutrients and chemical energy
- Catabolism – break down organic molecules to release energy at the cellular level
- Anabolism – use energy to create organic molecules at the cellular level
Energy
- Chemical energy- liberated when atoms are rearranged in molecules
- Electrical energy - energy exists by the separation of positive and negative charges
- Mechanical energy- kinetic energy of organised motion of molecules in the same direction.
- Heat (molecular kinetic energy)- energy of random atomic-molecular motion.
Work
- Physiological work – any process carried out by an animal that increases order.
- E.g. synthesis of macromolecules, generating electrical gradients by actively transporting
solutes across a membrane, and muscle contraction to move a limb.
Metabolism in animals
- All forms of energy are capable of doing work
- High-grade energy – capable of doing physiological work (Chemical energy, Electrical energy
and Mechanical energy)
- Low-grade energy – cannot do physiological work (Heat)
- Transformations of high-grade energy are always inefficient
- Efficiency of energy transformation = Output / Input
- Efficiency < 1 (or 100%) and energy lost as heat
- Glucose → ATP is 70% efficient
- ATP → Muscular motion is 30% efficient
- Therefore Glucose → Muscular motion is 21% efficient
- Conversion of chemical-bond energy to heat is irreversible
- Energy is not recycled
Maintenance of body temperature
- Poikilothermic: cold to the touch. Rates of heat production are low, they have poor
insulation, and heat produced is easily dissipated to the environment.
- Homeothermic: warm to the touch. Rates of heat production are high, they have good
insulation, and any heat produced is retained inside the body.
Metabolic rate
- Rate which chemical energy is converted to heat.
- Measure of heat production is Joules per unit time (Watts).
- Knowing the metabolic rate of species allows for the prediction of normal energy
requirements of individuals.
Measuring metabolic rate in animals
- Direct calorimetry- measure the rate at which heat leaves the animal’s body- direct measure
of metabolic rate, e.g. Lavoisier’s direct calorimeter.
- Indirect calorimetry- 1) measure the rate of respiratory gas exchange (mlO2/hour)=
respiration rate which can be converted to heat production if metabolic substrate is known.
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