Thermal Energy Notes

what does thermal energy influence

macromolecule structure and biochemical reactions

explain beta catenin and APC pathway

when the wnt signal binds, apc will unbind to beta catenin which binds to tcf and there is cell proliferation — apc is a tumor suppressor gene

explain the rate of reaction charts for enzyme s at different temperatures

• at too low of a temperature there is not enough collisions between a substrate and enzyme

• at just the right temperature the enzyme is at maximum output

• at too high of a temp the enzyme will denature

Eurythermal vs stenothermal

stenothermal enzymes can work in a very small temperature range whereas eurythermal enzymes have a larger range of temps they can work in — both still have one optimum temp

what does heat sinking mean

high thermal conductivity

Why does water have higher thermal conductivity than air and what does that mean in context?

water has more molecules per unit volume meaning there is a higher chance of molecules bumping into things and transferring energy. this means that you would freeze faster in a body of water than in air.

thermal strategy

controls the transfer of energy between the animal and the environment

what is the name of an organism whose body temp conforms to the environment

ecotherm

what is the name of the organism that maintains their body temperature using biochemical processes/metabolism despite their environment?

endotherm

metabolism

sum of all biochemical reactions; main source of thermal energy

how to organisms adapt to temperature

changes to surface area to volume ratio

bergmanns rule

a colder temperature lends itself to an animal with a higher body mass because the higher the body mass the slower the organism loses heat

allens rule

organisms in colder environments tend to have shorter appendages and are stockier

how does insulation work and give examples

insulation reduces thermal exchange and increases the distance over which thermal gradient extends — otters getting air in their coat or cardinals in thier feathers

regional heterotherms

• prioritizing maintaining regions within narrow thermal ranges

which parts of the body are heterothermic and why?

CNS, organs, brain — b/c this is an evolutionary advantage, heating the brain gives acuity, increases the rate of digestion - faster rate of nutrient assimilation

conditions needed for heterothermicity

• large body size

• heat source (muscle tissue)

• counter current heat exchangers (recapturing metabolic heat and bringing it back into the body)

example of a counter current heat exchanger

two veins right next to each other — veneous blood (coming from muscles) is warm and warms up the blood directly across from it — arterial blood flow (going back to the heart) — the blood loses temp as it hits the outside of the loop because that is the part of the vessel that is closest to the outside of the body

why do certain animals like swordfish have heating systems around their brains and eyes?

this is because they are predators so they need to be able to react quickly and detect the tiniest amount of movement

how is heat produced in these muscle organ heating systems?

heat is produced by the futile cycling of ca2+ between the sarcoplasmic reticulum and the inside of the cell — heater organs do not really have myofibrils so there is no contraction of the muscle just heating

process of futile ca2+ pumping

the cell is excited and the ca2+ release channel is activated. ca2+ is released into the interior of the cell which triggers using atp from the mitochondria to actively transport ca2+ back into the sr

thermoneutral zone

range of environmental temperatures within which the metabolic rates are minimal — metabolic rate will increase when outside of this region

compensatory responses

physiological responses to compensate that can return the operative temperature to the thermoneutral zone more quickly

• too cold — rise in metabolic rate to increase heat production — shivering

• too hot — physiological response to prevent overheating — sweating

thermogenesis

warming by heat from metabolism, digestion, and muscle activity

shivering

uncoordinated contraction of myofibers; short term heat production

examples of shivering in animals

• king penguins — shivering threshold

• pythons — low frequency spasmodic shivering in trunk muscles to warm up eggs

• insects — shiver to generate enough energy to fly — also have heat retention through long scales, dense fur coveirng thorax, and internally elongated air sacs

nonshivering thermogenesis in babies

placental mammals and hibernators have brown adipose tissue where there is a large number of mitochondria that produce heat; in liver or muscles and can also happen in babies

mechanism behind non-shivering thermogenesis

• increase in metabolic heat production without producing mechanical work — futile cycling of metabolic substrates in mitochondria

• heat production without ATP formation —- thermogenin (uncoupling protein in the inner membrane — this is a proton pump that prevents the body from tunring energy into ATP and rather turns it into heat) — there is citric acid cycling where the energy is lost as heat

short term adaptation to temperature

thermal acclimation — remodel cells, tissues, systems to alter sensitivity to temp i.e. change of nature of membranes, alter levels of critical enzymes, change tissue properties, change gill surface area

long term adaptation to temperature

cell machinery and enzyme biochemistru have evolved/adapted to organismal thermal ranges — proteins (open vs rigid)

homeoviscous adaptation and mechanism

• ecothermic animals change fatty acid chain length, saturation, phospholipid classes, cholesterol content

• because van der whaals forces hold membranes together ectotherms can change membrane composition to preserve fluidity

what do enzymes need to be?

• rigid to maintain conformation

• flexible to undertake conformational changes

what is impacted by temperature?

• protein structure — bond formation and 3d structure — impacts active site

• protein fluidity — structural changes required for catalysis

what is the thermal stability of enzymes related to?

related to the organisms thermal environment; adaptations in the structure of the protein are evident in relation to the ease at which enzymes can be thermally denatured

how do organisms cope with freezing?

• enzymes display cold adaptation — fewer weak bonds stabilize enzyme structure — rapid inactivation at high temp

• stress proteins induced at thermal extremes — molecular chaperones heat shock proteins

• ice nucleators control ice crystal growth in freeze tolerant animals — antifreeze proteins

what does HSP do?

use ATP to catalyze protein folding after translation — refolding thermally stressed proteins after theyve been damaged

how do ice nucleators work?

• cells secrete ice nucleators outside of the cell to control the location and kinetics of ice growth (calcium salt, alcohols, lipids) so that ice can’t poke holes in membrane

• they also produce intracellular solutes (cryoprotectants) to counteract ice drawing the water out of cells

• antifreeze proteins in insects and fish — bind to the outside of cells to stop ice from forming

how do freezing tolerant animals work?

• maintain homeostasis despite the lack of circulating fluids

• enzymes can tolerate low temps and high salt conc

• when frozen metabolic rate is depressed to hypometabolic (5-10% of normal functioning) during anaerobic glycolysis