Lecture Notes Flashcards
Acclimation and acclimitization
Physiological or biochemical responses that function to keep processes within homeostatic limits even with dramatic changes in ambient conditions.
Are organisms in complete equilibrium with their environment?
No. This creates gradients which encourages exchanges with the environment and the disruption of homeostasis.
Basic model of an enzyme catalyzed reaction
E+S –>ES complex–>ES activate complex –> P+E
Benefits of thermoconformity
- simplicity of various physiological systems
- don’t need systems to monitor environment
- don’t need underlying genetics or energy to production of receptors and systems
- don’t have to dedicate nervous system to thermoreceptors
- don’t need effectors to carry out instructions
Brown fat
Full of mitochondria. Can uncouple phosphorylation to produce heat. This would result in no proton motive force and proton leak would occur to release energy as heat instead of using it for ATP production.
Compare and contrast your cold-stress response with that of an Australian Aborigine. What seemed to be the priority for your response? For the Aborigine’s?
My cold stress response would be to vasocontrict and shiver to keep my body temperature up. An aborigine would vasoconstrict to lower the body temperature and conserve energy; would not shiver. The main concern for me would be to keep my body temperature up, for the aboriginie it would be to conserve energy
Conformation
Temp conforms to the temperatue of surrounds. If it’s constant than the animal’s temp will be constant too. Animals are adapted to temperature. Which means that physiological processes don’t function outside of certain conditions.
Conformation change
Enzymes need to be able to make a conformational change in order to bind with the substrate to make the product.
Costs of being a thermoconformer
- habitat constraints; too hot, too cold, too much flux
- dangerous at high or low Tb; tolerance limits
- temperature effects rates of biological processes; could lead to a decrease in efficiency of physiological systems
Costs of being a thermoconformer?
- habitat constraints: too hot, too cold, too much flux
- tolerance limits: dangerous if too high or low Tb
- temperature effects rates of bilogical process, decreases efficiency of physiological systems
Define catalyst
Catalyst are enzymes that lower the activation energy of a reaction to allow it to proceed. They are not consumed or permanently changed by the reaction.
Describe acclimation of sweating in humans over short-term (days) and ontogenetic time scales.
If humans are exposed to high heat for a period of 5-7 days, they will increase their sweating rates, but decreases the concentration of solutes in the sweat. In an ontogenetic time scale, humans lose sweat glands (through degredation) as they develop. Aren’t as sensitive to heat stress as you grow. The proportion of sweat glands lost depends on the enviroment you live in.
Describe shivering
Short-duration, low-tension, contraction-relaxation cycles. This response requires energy and interferes with locomotion. It also disrupts the insulation layers.
Describe the physiological response of a wolf whose foot is exposed to severe cold stress. Compare that with the response we’d expect to observe in you, and in an Inuit.
For a wolf, the immediate response is to vasocontrict in the paw and then vasodialate before it gets to freezing in cycles of contriction and dilation in order to conserve energy. In ‘me’ the response would be to vasocontrict in all my appendages in order to keep my core warm and conserve energy. This could cause a decrease in function of appendages. In an inuit, the reponse is to vasodilate and keep appendages at a constant temperatue and functioning. Is very energetically expensive.
Discuss how S and modulators can affect reaction rate
- increase in S increases rate of reaction
- increase substrate and presence of a negative modulator has no effect on reaction rate.
- decreased substrate and a positive modulator has no effect on reaction rate.
Graph showing the difference between a regulator and a conformer
Ectotherms and acclimation
Tuning of preferred temperature to the general habitat Ta conditions. In constant environments this leads to tendency to lose acclimation and acclimitization ability.
effector
Any structure that helps restore the desired internal condition
Enymology
Physiology of enzymes
Enzyme-substrate affinity
Ease of binding of substrate to the active site; ability to bond. The higher the affinity the quicker the reaction will proceed.
Epithelial cells and transport
Have proteins to regulate transport of ions, water, nutrients, wastes. No molecule can enter or leave body without crossing epithelium. Homeostasis is possible because epithelia control exchange
Examples of ontogenetic changes
One example is sweat glands. Sweat glands degenerate with growth because you are not as sensitive to heat stress. The amount of sweat glands that degenerate depends on your environment. If you live in the tropics you would have less degeneration. Once sweat glands degenerate the do not regenerate.
Explain dTb/dt= -CA(T0-TA)
Heat exchange is effected by the thermal conductance, (the rate of heat loss for an organism), surface area of the organism and the difference between the temperature of the body and the temperature of the environment (ambient).
Explain Newton’s law of cooling (heat exchange)
rate of heat exchange is equal to ease of which heat can be exchanged times the magnitude of the gradient (driving force)
Explain the costs of adaptations in terms of ecology and evolution.
Every adaptation comes with a trade off. Regulators are able to live in more broad habitats and are not as dependent on the conditions in their environment. Conformers are able to expend less energy and processes for regulation but they are limited by their environment because their preferred may not exist, and when they are taken out of their enviroment they cannot survive.
Homeostasis
Defined as stability in chemical and physical conditions within an animals cells, tissues, and organs despite changing environmental conditions. Kept within a tolerable level (pH, temp, Ca++)
How do birds and mammals facilitate evaporative cooling? Is there a drawback to the mechanism(s) they employ?
Gular flutter, beaks open, flap under beak fluttlers. Drawback would be energy?
How do ectotherms benefit if they’re able to maintain their body temperature at Tpref? Can you offer a possible explanation for this?
They are able to maximize growth, development, and fecundity. This is because they do not have to spend time and energy to maintain their body temperatures and can allocate energy to growing and reproducing.
How do endotherms adjust to long term cold temperatures?
Increase synthesis and release of thyroxine (produced by thyroid and triggered by thyroid stimulating hormone) and prolactin.
How do gradients and exchanges relate to homeostasis?
The cells maintain gradients so that they can access substrates that they need in order to maintain homeostatic balances.
How do humans acclimate to high ambient temperatures?
Humans respond to heat stress over periods of more than 5-7 days. They increase sweating rates and decrease the solute concentration in the sweat in order to conserve the solutes.
How do modulators work?
They work by changing the shape of the active site. Negative modulators inhibit the activity of an enzyme. Positive modulators activate the enzyme.
How does a substrate bind to an active site
H bonds, van der Waals, Hydrophobic, etc
How does an endotherm maintain its temperature in the TNZ without changing its metabolic rate?
Endotherms make use of blood shunting; which is cheap energetically. When the endotherm is hot it can increase blood flow closer to the skin which allows for more heat loss and cools the animal. When it is cold, it can increase blood flow to the core so that it does not lose as much heat.
How does enzyme-substrate affinity affect reaction rates?
Higher affinities allow for higher reaction rates
How do thyroxine and prolactin affect LCT?
It lowers the LCT. Increase insulation effectiveness by reducing the thermal conductance of the insulation.
How is precise tuning of funtion to ambient temperature beneficial?
Increases efficiency, inceases growth and fecundity and maximizes fitness
How is the temperature regulation different for the periwinkle in summer and winter?
In the summer and winter the TNZ is different (lower in the winter months). This is made possible by the production of isozymes.
If Ta is relatively constant
- can fine tune enzymes, physiology systems to work well and maximize efficiency
- maximizes survival and reproduction (fitness)
Importance of driving force in homeostasis
In heat regulation, the temperature gradient is the driving force for an organism to exchange heat with its environment. And the rate of the heat exchange between the environment and the organism.
integrator
evaluates incoming sensory information and “decides” whether a response is necessary to acheive homeostasis
Intermediate time scale
Longer than the time it takes transcription and translation to occur, but shorter than the lifespan on the organism
Isozymes
Enzymes that perform the same function but at different temperatures (at different conditions). This is done by new gene expression for the enzyme. A single aa substitution near the C terminus allows the enzyme to shift optimum temperature.
Lock and key model
Enzymes have a high specificity for substrates.
Long term time scale
greater than lifespan (evolution).
Example: epigenetics
Metabolic disruption
changes the ratios of metabolic products; can impact outputs in huge ways
Alzheimers ration of phosphatidychlorine and phsophatidylethanolamine is different than “normal”
metabolic rate
- measure O2 cosumption rate
- indirect measure of energy consumption/production
- reflects overall health and ability of homeostasis
negative feedback
effectors reduce or oppose change in internal conditions when a molecule level becomes too high.
Newton’s law of cooling (heat exchange)
Rate of heat exchange is equal to ease of which heat can be exchanged times magnitude of the gradient. Increased area increases ease of heat loss.
Non shivering thermogenesis
Triggered by norepinepherine and epeinepherine. Increases glycolysis and lipoltsis. In humans this increases metabolic rate by 25% over BMR
Ontogenetic time scales
during development. An example of this would be sweat glands
Osmoconformers
allow concentrations to fluctuate wiht environment. most marine invertebrates are osmoconformers, many freshwater invertebrates.
