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BIOL370 Study Guide - Final Guide: Myosin Head, Pressure Measurement, Sensory System

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Dinu Nesan
Study Guide

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Lecture 11: Adjusting Metabolism
- Hypometabolism is a strategy for reducing energy expenditure in response to adverse environmental
o Torpor, hibernation, estivation
- Examples can be found in almost all animal orders
- Regulation of hypometabolism is multi-part
o Hormonal input, reversible phosphorylation, selective transcription
- Metabolism: Sum of all processes by which energy is acquired, transformed, and channeled into useful
functions to sustain life (energy for growth, reproduction, structural maintenance, & responses to the
- Food energy Metabolizable energy Fuel metabolic processes (Heat is generated as a waste product)
- Metabolic rate = Rate of energy consumption (Energy/unit time)
o Determines how much food an animal needs, the total activity of all physiological mechanisms & the
pressure on energy supplies in the ecosystem
- Respirometry: Measures the animal’s rate of respiratory gas exchange (O2 consumption & CO2 production)
o Indirect measurement because it assumes that
Chemical reactions are aerobic (oxidative phosphorylation, not anaerobic glycolysis)
Heat produced with volume of O2 consumed is constant regardless of different types of
energy substrate
Oxygen is NOT stored within the body
C6H12O6 + 6O2 6CO2 + 6H2O + 2820kJ (CO2/O2 = 1.0 for carb, 0.7 for lipids & 0.8 for protein)
o Open respiratory: O2 meters @ both ends or with a mask, continuous monitoring
o Closed respiratory: Injection of pure O2 to balance out the colored water movements of manometer
- Adjustment of metabolic rate due to environmental factors
o Extreme environmental conditions Disturbances in homeostasis
Decrease in TA Increase in thermogenesis & metabolism Constant TB
o Animals that enters hypometabolic states can alter TB set point at thermostat center pre-optic
anterior hypothalamus Recalibration, defend low TB instead of compensates
Decrease in TA Decrease in thermogenesis & metabolism Decrease TB
- Hypometabolism “Hypoxic Metabolic Suppression”
o Reduce metabolic rate below basal metabolic rate “normal”
o Establishment of a new, lower energy expenditure set point (Energy expenditure < Intake + Stores)
o Allows the animal to survive adverse environmental conditions
o MR depression varies in duration, magnitude (up to 95% decrease) & physiology
- Types of Hypometabolism
o Torpor (Daily heterothermy switchers from poikilothermic & homeothermic)
Few hours, depresses metabolic rate due to temperature effects (Lower TA at night)
E.g. Rufous hummingbird (heart rate drops from 1000bpm to 80bpm)
Torpor onset when temperature drops below 8⁰C, little energy needed to maintain TB,
much less O2 consumption than normothermal TB
o Hibernation (over-winter)
Metabolic rate can be suppressed to 2-5% of basal metabolic rate
E.g. Underwater hibernating turtle (180days) uses the same amount of ATP to normoxic
turtle at 20⁰C (1day)
E.g. Freezing frogs, up to 65% of body can be converted to ice, can allow the body
temperature to drop below freezing, no evident metabolism
o Estivation
Similar to hibernation, but in response to hot conditions
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