BIOL1131 Lecture Notes - Lecture 4: Psychrophile, Energy Economics, Countercurrent Exchange
7 Jun 2018
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Comparative Animal Physiology: Metabolism and Energetics
• What is animal physiology?
o How organs and organ systems work
▪ E.g. cardiovascular, digestive….
o Physiology extends down to cell biology so we can understand
how the systems work
o Physiology extends up to organisms so we can understand what
the systems do
• So what is comparative animal physiology?
o It is how animals work relative to other animals
o The general physical and chemical constraints are the same for all
animals so they fundamentally work the same way
o However, there are variations
• Metabolism – the fire of life
o Cell metabolism is the use of energy and catabolism/anabolism of
organic molecules
o Animal metabolism is the overall direction of biochemical
reactions; it defines animal life
o Physical laws dictate energy exchange and transformation in
animals just as in non-biological reactions, so it is important for
biologists to understand the physical laws of energy and heat
exchange
o Metabolic rate of animals depends on a number of factors,
including activity level, body mass, cellular complexity, phylogeny
and body/ambient temperature
• Energy – thermodynamics
o The study of the relationship between heat and other forms of
energy
o First law – energy is conserved, it cannot be created or destroyed
o Second law – there is an inevitable degradation of useful energy
into heat
• Closed systems
o In a closed system, the total energy content is constant
o The universe is a closed system
▪ Has constant energy content
▪ This energy is being constantly degraded to heat, and the
system will eventually run down
• Open systems
o There is an input/loss of energy content
o The earth is an open system
▪ Continually gains an immense amount of energy from the
sun as solar radiation and loses energy by radiation
▪ Animals are open systems – they gain energy by consuming
matter and is lost through metabolism and energy
expenditure
• Cellular metabolism
o Is one of the basic and universal attributes of life. It is essentially
the synthesis of a biologically useful form of energy (ATP) and its
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use; the maintenance of the special environment inside cells. This
intracellular environment has a different concentration of many
important organic molecules and inorganic ions. Maintaining these
solute gradients requires the expenditure of energy.
• Glycolytic (Anaerobic) metabolism
o Glucose → 2 lactate + 72kJ/mole heat energy + 2 ATP
o 2 ATP → 45 kJ/mole
• Aerobic cellular metabolism
• Where did O2 come from?
o Plants appeared and produced oxygen as a byproduct of
photosynthesis to the current level of about 21% of the
atmosphere
• Animal metabolism
o There are a variety of ways to measure metabolic rate:
▪ Substrate utilization
▪ Oxygen consumption
▪ Carbon dioxide production
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