Biology 2601A/B Study Guide - Goby, Molecular Mass, Volumetric Heat Capacity
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Organismal Physiology Lecture No.1: Temperature I
Tuesday September 11th, 2012
-Human beings are one of the few organisms that inhabit environments that encompass both
temperature extremes. Accomplishing a feat most organisms cannot, they are able to do this through
the production of suitable shelters, tools, cultures, etc.
-Other life forms usually preside in one extreme environment, like penguins in the Antarctic and Baobab
trees in the African savannah, and find more primitive solutions to surviving under such conditions.
-Temperature is defined as the measure of the speed or intensity of the incessant random motions that
all the atoms and molecules of any substance undergo on an atomic/molecular scale. More exactly, the
temperature of a substance is proportional to the product of the mean-square-speed of the random
molecular motions and the molecular mass.
Distinction Between Temperature & Heat:
-While temperature is the intensity of motion by the atoms vibrating in an object, heat can be defined as
the amount of energy present in an object. It is temperature that determines the direction of heat
(energy) transfer, which is always from warmer to cooler conditions.
The Energy Balance Equation:
-Energy balance can be calculated according to the following equation: R (radiation) + H (convection) + C
(conduction) + M (metabolism) + L (latent heat) = 0. When the sum of these factors is zero, the energy
content of the organism is balanced; it is neither gaining nor losing energy.
-Radiation energy can impact organisms directly (either from the sun or the atmosphere), indirectly (by
reflecting off of other organism and their environment), or it can be emitted by the organism itself.
Convection describes the movement of heat energy through fluid mediums (e.g. wind chill), while
conduction describes the transfer of energy through solid mediums (e.g. hot rocks, soils).
-Metabolic heat production is determined by the amount of O2 consumption and is coupled with latent
heat, the amount of water evaporation or condensation present in an organism (either through
breathing or off the surface of skin).
Common Biological Temperatures:
-(-80°C) hardened conifer leaves still survive. (-0.6°C)
-(15°C) developmental threshold for many plants. (37°C) body temperature of most mammals.
-(53.6°C) highest recorded temperature of a metazoan. (50-70°C) most proteins denatured.
Classifications Of Thermal Biology:
-Endotherms generate internal heat.
-Ectotherms rely on external temperatures to determine body temperature
-Homeotherms defend a constant body temperature
-Poikotherms Allow body temperature to vary.
-Heterotherms have more than one temperature set point, or switch between homeo/poikothermy.
-Regional endothermy/heterothermy Different body temperatures in different parts of the body.
-As oxygen consumption corresponds to metabolic activity, metabolism can be calculated according to
the following equation: M (metabolic rate) = a (constant) x 10 n (constant) x T
-Logarithmically, the equation can be modified to a linear form (y = mx + b): log(M) = nTb + log(a)
The Temperature Coefficient:
-Q10, also known as the temperature coefficient, is the ratio of the rate of a process at one temperature
over the rate of the same process at a temperature 10°C lower. In other words, Q10 calculates how much
the rate of metabolism changes for every 10°C drop in temperature.
-A formula for this concept would look as follows:
Q10 = RT (rate of metabolism at temperature x) / R(T-10) (rate of metabolism at temperature x - 10)
-Because the temperature metabolic rate relationship is not exactly exponential, the impact of a change
of temperature varies with temperature; Q10 is not constant. The same relationship with Q10 holds true
for plant functions like respiration.
-If Q10 is approximately equal to 1, a physical or chemical process is taking place. If Q10 is approximately
in between 2 and 3, a biological process is taking place.
Cause Of Temperature Changes:
-Temperature determines motion and therefore the rate at which molecules encounter one another;
more interactions = more reactions.
-Temperature also determines the conformation and efficiency of enzymes (Q10 2-3 in biological
systems); most enzymes have a temperature optimum.
Enzymes & Temperature:
-A broad representation of how enzymes function is that they will act on a specific substrate (that fits
Temperature can affect the rate at which the substrate and enzyme encounter one another as
moderately warmer temperatures account for increased encounters and therefore more reactions
site and result in a weaker enzyme affinity for its substrate (fewer reactions occur).
Enzyme Catalytic Terms:
-Vmax the maximum velocity/rate of reaction possible for a given enzyme.
-Km max; a function of the
-D structure and thus temperature.
-Kcat the number of substrate molecules processed per unit time at saturation point.
Enzyme Affinity Changes With Temperature:
-In the case of the goby fish, the normal temperature range for enzyme operation is from around 20-
substrates, resulting in tight binding in their active sites and thus, slower reaction rates.
resulting in loose binding (denaturation) in their active sites and thus, reactions are less likely to occur.
--bond energy to heat
and external work. This rate is determined by enzyme activity and thus, is temperature-dependent.
Ectotherm Processes Governed By Temperature:
-Processes in ectotherms that are temperature-dependent include: activity level (e.g. reptiles), muscle
contraction (e.g. evading predators), locomotive speed (e.g. chasing prey), digestion (e.g. longer
digestion in colder temperatures), growth (e.g. faster development in warmer temperature),
germination, photosynthesis, and fruit production/ripening.
Human beings are one of the few organisms that inhabit environments that encompass both temperature extremes. Accomplishing a feat most organisms cannot, they are able to do this through the production of suitable shelters, tools, cultures, etc. Other life forms usually preside in one extreme environment, like penguins in the antarctic and baobab trees in the african savannah, and find more primitive solutions to surviving under such conditions. Temperature is defined as the measure of the speed or intensity of the incessant random motions that all the atoms and molecules of any substance undergo on an atomic/molecular scale. More exactly, the temperature of a substance is proportional to the product of the mean-square-speed of the random molecular motions and the molecular mass. While temperature is the intensity of motion by the atoms vibrating in an object, heat can be defined as the amount of energy present in an object.