Comparative Physiology Exam 1

Proximate explanations

explanations of mechanisms, processes, or pathways, how something works

Ultimate explanations

evolutionary explanations, adaptive significance, how something came to work that way

Physiological stress

a perturbation (deviation) away from the optimal range of conditions

Stressor

an environmental change that causes the perturbation away from optimal conditions

Thermal compensation

the ability to adjust internal functions to maintain stable physiology

Pro/con of temperature conformity

energetically cheap, but biochemical reaction rates are not always optimal

Pro/con of temperature regulation

cells are kept reliably in optimal range, but it’s energetically costly

Adaptation

changes in populations over generations by natural selection, characterized by genetic changes over generations

Acclimation

a chronic response to a changed environment, where old and new environments differ in one or two highly defined ways laboratory phenomenon)

Acclimatization

a chronic response to a changed environment, where old and new environments are natural environments that can differ in numerous ways (ex. summer & winter, low & high altitudes)

Phenotypic plasticity

genetically identical, but the phenotypes can be different due to environmental conditions

Marginal stability

macromolecules aren’t too rigid where the protein can’t flex into correct shape for binding, and they aren’t too flexible where the substrate can’t bind. It’s in between, which allows substrate binding

Eutrophication

high nutrients in water → increase growth in organisms → algae decomposes → oxygen supply is used up, leaving water depleted of oxygen

Osmoconformers

a marine organism that matches its internal salinity to the environments salinity

Osmoregulation in freshwater fish

tissues are hypertonic relative to environment (water enters, salt leaves)

Osmoregulation in salt water fish

tissues are hypotonic relative to environment (salt enters, water leaves)

What if hemoglobin has an affinity too low for oxygen?

oxygen is difficult to load into hemoglobin

What if hemoglobin has an affinity too high for oxygen?

oxygen is difficult to unload from hemoglobin

How does a membrane compensate at higher temperatures?

membranes are more intrinsically rigid, have more saturated proteins

How does a membrane compensate at lower temperatures?

membranes are more intrinsically fluid, have more unsaturated proteins

Choline head group affect on fluidity:

greater packing, more rigid

Ethanol head group affect on fluidity:

less packing, more fluid

What does a higher PC/PE ratio mean?

there’s greater rigidity

How can thermal compensation be acclimation/acclimatization?

when fish living in lower temps get moved to higher temps, they’ll change their membrane composition to be more rigit to adjust to the new temperature

What types of weak interactions lead to protein folding/conformation?

Hydrogen bonding, ionic bonding, and van der Waals interactions

How does the voltage-gated sodium channel work?

voltage sensor and pores are covalently bonded, so when voltage changes, it’s sensed and opens up the channel (or closes it)

Molecular chaperones

assist proteins in folding

Orthologs

created by speciation, on same locus in genome

Paralogs

created by gene duplication, on different loci in genome

Heat-shock response

a cellular stress response

Aspects of cellular stress response

1. induced by unfolded proteins in cell

2. targeted expression of HSP

3. Extremely fast

4. transcriptional response

What is the process for synthesizing HSP?

unfolded protein in cell present → HSF1 dissociates from HSP and forms trimers → HSF1 trimers associate and induce transcription of HSP gene

k

rate constant/reaction rate, # of molecule collisions per second

e^-E_a/RT

probability of successful collisions, when temp increases, this decreases

Q₁₀

the effect of a 10ºC increase in temperature on reaction rate

• greater Q₁₀ means greater activation energy

k_cat

catalytic rate constant, measures enzymes effectiveness

• the amount of substrate converted to product per enzyme molecule when fully saturated w/ substrate

k_m

the substrate concentration at which the reaction velocity is half the max velocity

• low K_m indicates high affinity of enzyme for its substrate

Mechanisms of enzyme regulation

gene expression/protein degradation, allosteric modulation, and covalent modulation

Allosteric modulation

binds to allosteric site, can inhibit or activate the enzyme based on conformational change to the active site

Covalent modulation

chemical reaction that break or make covalent bonds between modulators and enzymes

• ex. phosphorylation + dephosphorylation, protein kinase

How can enzymes be used to reveal evolutionary relationships between genes?

1. infer the ancestral amino acid sequence (using outgroups)

2. find amino acid substitutions (different from ancestral)

3. Enzymes that share the newly evolved substitutions are presumed more closely related to each other than those without substitution

Acute response

immediate response to stressor; i.e covalent modulation, allosteric modulation

Chronic response

response over days to stressor; i.e. gene expression

Evolutionary responses

mostly permanent changes adapt enzymes to environmental changes

Daily cycles (time scale)

things constitutively expressed, ready to turn off/on

• acute mechanisms

Developmental responses

similar to chronic responses, where changes occur over multiple days

Heat

thermal energy, the amount of random kinetic energy of particles in a system

• scales w/ size

Temperature

the average random kinetic energy of particles in a system

• does not scale w/ size

• determines direction of heat transfer