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Lecture 7

Lecture 7 - Metabolism II - Plasticity

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Biology 2601A/B
Graeme Taylor

LECTURE 7 – METABOLISM II: PLASTICITY  Animals can conform and regulate at the same time  Water temperature may be considerably warmer in rivers, so body temperature of salmon would also increase  Conforming with regards to temperature but maintaining with regards to chloride concentration Homeostasis  Homeostasis – internal constancy and the physiological regulatory systems that automatically make adjustments to maintain it (in terms of animals)  Blood flow, heart rate, breathing rate, etc. – not actively being controlled  Condition of stable internal environment which usually requires extensive feedback mechanisms (in terms of plants)  How does homeostasis work? o By having bodily sensors constantly monitoring body temperature with reference to a set point (the standard for body temperature) – works like a household thermostat o When body temperature deviates from set point, sensors signal physiological processes to commence and regulate body temperature o When preferred body temperature is reached, sensors stop sending signals and negative feedback loop comes to a stop Control in Homeostasis  Hormonal – for example, insulin and glucagon regulate mammalian blood sugar  Molecular – for example, many cell-signaling pathways that regulate cytoplasm composition  Nerve-mediated – for example, vaso-constriction and vaso-dilation regulate heat loss in vertebrates  Biochemical – maintaining rates of reaction by altering pathways and enzymes Positive Feedback  Rare in biology – results in amplification of the deviation from the setpoint o Example – albedo and climate change o Fairly big chunk of ice (glacier) - when radiation from the sun hits that, ice has a high albedo (white), and thus very reflective - a lot of the radiation is bounced back off and reflected back to the atmosphere - thus does not warm the surface of the earth o Leads to positive feedback whereby more energy is absorbed from sun and more ice is melted o Issue associated with climate change and more problematic with higher altitudes 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  Compensation is a way of maintaining a constant rate even if there are changes in the environment  Some species of ectotherms settle for no compensation and thus, their body temperature is dictated by the environment  After compensation, rate of metabolism will be lower than normal o Graphically expressed – less steep curve, smaller slope Acute Perturbations can come from Mismatches in Pathways  Rates of pumping in vs. diffusion out of ions  Rates of production vs. use of reducing equivalents o Temperature effects on photosynthesis  In ETC of photosynthesis, there are three main types of processes in relation to temperature: o Fast physical processes – largely temperature independent (very fast absorbance of light) o Diffusions that are a bit temperature dependent (electron shuttling) o Enzyme catalyzed processes – quite temperature-dependent + (NADP reduction
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