BIOB34H3 Lecture Notes - Lecture 3: Photon, Heat Shock Factor, Communist Party Of The Peoples Of Spain
THERMAL PHYSIOLOGY
How Temperature Affects Performance
-Eliason UBC (Farrell lab)
-Temp affects the performance of animals
-Studied effects of ambient temp. on the
aerobic scope (MMR – SMR à reflects the
max. amount of energy the animal can
devote to doing stuff like swimming [is
basically the energy available to do other
things to reach the MMR]) on sockeye
salmon
-Find that in cold temp or at 25, the AS is
basically zero à thus can’t swim
-Between 15-17* is when they have most
energy available to do other stuff
-OCLTT (Oxygen and capacity limited
thermal tolerance) hypothesisà in many cases, the thermal tolerance of animal is
determined by oxygen à can’t tolerate temp. above/below their range, so their AS is
almost nothing à thermal tolerance of animal is dictated by their metabolic capacity
better AS = faster you can swim = faster reach their sites for reproduction
Sockeye in the Fraser river is much less now à Fraser river’s temperature is increasing à
2*C increase shows that around 20-22*C, their AS is much, much lower (cut by 50-75%)
= less energy to swim to Fraser river = get there late or produce weak offspring = low
numbers for the sockeye salmon
-Cohen Commission à Sockeye salmon are important for food, cultural value etc.
-Temp. can profoundly affect the performance of animals
REACTION RATES
-Not all enzymes are equally thermally-sensitive, so this may mean also that temperature
disrupts metabolic pathways.
-First physical effect on animals is on their
reaction rate à as temp. is increased, the rate
of the rxn initially increases (increases b/c
collision theory [ in order for molecules to
react, they have to collide and collide w/
sufficient amount of energy] è see this as the
energy of the reaction as it occurs (see in the
transition state, the Energy is very high) à
when the particles collide, if they don’t have enough energy to react, they won’t have a
reaction à that’s why reaction rates tend to increase when temp. is increased
at cold temp. molecules are not very energetic à when they collide, the likelihood of a
reaction occurring at a low temp. is then much lower
find more resources at oneclass.com
find more resources at oneclass.com
at higher temp. à molecules are moving around more à
when they collide, they’re likely to have a reaction b/c
have more energy to be able to reach the transition rate,
that’s why temp. causes reaction rates to increase initially
-* generally as you increase temp, rxn rates get faster à b/c
increase temp = molecules move more = more energetic = collisions are energetic
enough to reach transition state à thus warming up molecules = greater chance of rxn =
faster rate of rxn*
-find that further increases in temp results in rxn rate decreasing
à b/c most rxns are catalyzed by enzymes (who stabilize
transition states and rxns and make them have less energy) à
thus enzymes increase RR (by lowering energy) à however, if
increase temp. too much, enzymes denature = lose enzymatic
activity b/c denatures = loss of enzyme = reaction rate then
sharply begins to decrease again
-Enzymes denature b/c component molecules of the protein
might be moving so fast that they move so fast/much that they break the bonds
holding them together = denaturation (they
exceeded that strength of the bonds that are holding
the protein shape together)
-Diff. kinds of bonds work to hold proteins together
hydrophobic interactions à non-polar parts of proteins
interacting w/ eachother à weak
hydrogen bond à weak
ionic bonds à stronger, resists high temp.
disulphide linkages à stronger, resists high temp.
-org. could possibly combat this by making enzymes that have only ionic/disulphide
bonds, but that doesn’t work biologically
find more resources at oneclass.com
find more resources at oneclass.com
ENZYME STRUCTURE
-Induced fit model for enzymes: there isn’t a perfect complementarity of structure
between the 2 (reactant and enzyme), but idea is that as the reactant bonds to the
enzyme, the enzyme is flexible enough to caress and accommodate the substrate
requires flexibility in the structure of the enzyme à the reason we don’t have a lot of
very strong bonds, is because we
want enzymes to be flexible enough
to accommodate the substrates à
trade-off between strength and
flexibility in enzymes
-Animals: are aware of this trade off
à animals have built enzymes
depending on the temp (are strong
or flexible dep. On the temp)
eg. Lactate dehydrogenase in 4
diff. reptile species and tried to see
its maximal activity over 4 range of
temps à desert iguana has a
preferred body temp of 39*C (thus
its lactate dehydrogenase should be functional at that temp) à find that the enzyme of
the desert iguana (LACDHY) has the highest activity at the highest temp à b/c their
version of the enzyme is being held by strong bonds (Eg. Ionic, disulphide) – does not
denature that quickly
how is the enzyme flexible enough to function then? à flexibility comes from it
functioning in high temperature à higher temps allow it to be flexible enough to
accommodate reactants
eg. When see colder temps, see that the desert iguanas enzyme is the least reactive at
the coldest temp à b/c not enough heat to allow it to be flexible = not enough activity to
move enzymes components = strong bonds = rigid = greatly decreased activity
eg. California alligator lizard à has highest activity at colder temp à b/c enzyme is held
mostly by weak bonds, and is thus very active at colder temps à @ higher temps, when
the weak bonds are subjected to higher temps, the enzyme is more susceptible to be
denatured = function much less in higher temps
-Species have evolved enzymes best suited for their normal body temp
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Find that in cold temp or at 25, the as is basically zero thus can"t swim. Between 15-17* is when they have most energy available to do other stuff. Better as = faster you can swim = faster reach their sites for reproduction. Sockeye in the fraser river is much less now fraser river"s temperature is increasing . 2*c increase shows that around 20-22*c, their as is much, much lower (cut by 50-75%) = less energy to swim to fraser river = get there late or produce weak offspring = low numbers for the sockeye salmon. Cohen commission sockeye salmon are important for food, cultural value etc. Temp. can profoundly affect the performance of animals. Not all enzymes are equally thermally-sensitive, so this may mean also that temperature disrupts metabolic pathways. At cold temp. molecules are not very energetic when they collide, the likelihood of a reaction occurring at a low temp. is then much lower.
