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Lecture 4

Biology 2601A/B Lecture Notes - Lecture 4: Rainbow Trout, Thylakoid, Phosphorylation


Department
Biology
Course Code
BIOL 2601A/B
Professor
Jennifer Taylor
Lecture
4

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Lecture 4: Metabolism II
PLASTICITY
Animals can conform and regulate at the same time to
changing conditions (i.e. temperature)
- Animals can have some things be in
homeostasis but others vary at the same time
- Picture: blood temperature increases as water temperature increases
- But blood [Cl-] doesn’t increase as water [Cl-] does
Homeostasis
The condition of a relatively stable internal physiological environment, usually
involving extensive feedback mechanisms
Works in a feedback loop:
- Body temperature is sensed by the sensor, which is compared to the set point
- Then you have regulatory mechanisms that effect the body temperature,
- There’s a feedback loop determining which systems need to be up or down-
regulated to keep the body temperature at the set point
Negative Feedback
Works to return the value to the set point
Too hot  increase heat loss (vasodilate, pant)  body cools towards set point
Too cool  decrease heat loss (vasoconstrict), increase heat production  body
heats towards set point
Control in Homeostasis
Hormonal: ex. Insulin and glucagon regulate mammalian blood sugar
Molecular: ex. Many cell-signaling pathways that regulate cytoplasm composition
Nerve-mediated: vasoconstriction and vasodilation regulate heat loss in
vertebrates
Biochemical: maintaining rates of reactions by altering pathways and enzymes
Positive Feedback
Its rare in biology
It results in an amplification of the deviation from the set point
Ex. Albedo and climate change
- Albedo means whiteness
HWA 1.7
Animals can conform and regulate at the
same time…

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- At high latitudes there sea ice, and as the sun and the radiation heat come
down, it hits the dark water and gets absorbed
- Starts melting ice, the more you melt the ice, the more you expose the dark
water that will absorb heat, and then more ice melts, and then more theres
more water, so more heat is absorbed, so more ice melts, etc.
Compensation
Maintain performance in the face of varying conditions
- Requires a shift away from the acute response
- Plasticity on the order of hours to days to weeks
This is an acute response that you want to do when the environment
instantaneously changes on you
Lake Erie Water Temperatures
No compensation, so the metabolic rate changes with the temperature
Some species settle for this no compensation
Could use biochemistry to blunt acute changes
- Enzymes are extremely temperature sensitive, so they can use biochemistry to
maintain a somewhat constant substrate affinity across
various temperatures
Graph: no compensation here, but no acute effects to
compensate for
- If you are maintain the same enzymatic rate across the temperatures, you don’t
need to compensate for anything
After Compensation
There is a shape change in the response curve
Metabolic rate increases exponentially with
temperature
Lake Erie Water Temperatures
M o n t h
J a n f e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
T e m p e r a t u r e ( C )
0
5
1 0
1 5
2 0
2 5
High metabolic rate
Low metabolic rate
No compensation... But no acute effects
to compensate for
M o n t h
J a n f e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
T e m p e r a t u r e ( C )
0
5
1 0
1 5
2 0
2 5
K
m
After compensation: shape of response
curves modified
M o n t h
J a n f e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
T e m p e r a t u r e ( C )
0
5
1 0
1 5
2 0
2 5
High metabolic rate
Low metabolic rate
Temperature
MR
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The dotted line is the process you see in summer
Over the course of the year, you see shift in biochemistry and you bring the
metabolic rate up the solid curve
It’s the same metabolic rate, just changed over time through physiological means
Plants
Mitochondrial respiration in black spruce grown at
two different temperatures
Cool-grown: respiration increases exponentially
with increase in temperature
Warm-grown: also exponential but shifted
If you take the night time temperature where the
plants are growing at night, you can see the
respiration rates are similar
This is an example of compensation
Disruption in Pathways
Acute perturbations of homeostatic can come from mismatches in pathways
- Not having processes balanced out is problematic
Rates of pumping in vs. diffusion out of ions
- If its not matching, no homeostasis for concentration inside the cell
Rates of production vs. use of reducing equivalents
- Temperature effects on photosynthesis
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