MS4- metabolism in conformers and regulators

• At the heart of metabolism are enzymes. It is the enzymes that regulate each and every reaction
• For metabolism to remain efficient, enzymes should be in an environment that is maintained within fairly narrow parameters; extremes should be avoided as this would lead to denaturing of the enzymes
• The ability of an organism to maintain its metabolic rate is affected by external abiotic factors such as pH, salinity and temperature
• Some organisms can do little to regulate their internal environment (conformers) while others take extensive measures to regulate their internal environment (regulators)
• Conformers internal environment is dependant upon external conditions
• Conformers use behavioural responses (eg basking, burrowing) to allow them to tolerate variation in their external environment to maintain optimum metabolic rate
• Conformers have low metabolic costs
• Conformers have a narrow range of ecological niches
• Regulators maintain their internal environment regardless of the external environment
• The regulation of the internal environment is called homeostasis
• Regulators use metabolism to control their internal environment
• This regulation requires energy to achieve homeostasis
• This increases their metabolic costs
• Regulators have an increased range of possible ecological niches
• In negative feedback when a condition changes, the opposite effect is produced by the body to return itself to normal
• Although humans can withstand a wide range of environmental temperatures, we need to keep our internal body temperature as close to 37c as possible. This process is known as thermoregulation
• Thermoregulation is an example of negative feedback control
• Regulating temperature (thermoregulation) is essential for optimal enzyme activity and high diffusion rates to maintain metabolism
• The hypothalamus, located in the brain, is the temperature monitoring center.
• Thermoreceptors in the hypothalamus detect changes in the temperature of the blood, which correspond to temperature changes of the core of the body
• Thermoreceptors in the skin detect changes in the surface temperature and send messages, via nerve impulses, to the hypothalamus
• The hypothalamus processes the information it receives from the thermoreceptors and decides what response is needed
• Information is communicated by electrical impulses through nerves to the effectors in the skin
• Effectors bring about corrective responses to return temperature to normal
• The corrective responses to an increase in body temperature include:

  • sweating
  • vasodilation of blood cells
  • decreased metabolic rate
• During sweating body heat is used to evaporate water in the sweat, cooling the skin
• Vasodilation (widening of blood vessels) results in an increased blood flow to the skin increasing heat loss by radiation
• A decreased metabolic rate results in less heat being produced
• The corrective responses to a decrease in body temperature include:

  • shivering
  • vasoconstriction of blood vessels
  • hair erector muscles contracting
  • increased metabolic rate
• Muscle contraction generates heat during shivering
• Vasoconstriction (narrowing of blood vessels) results in decreases blood flow to the skin decreasing heat loss
• Hair erector muscles contract, raising the hairs and trapping a layer of insulating air
• An increased metabolic rate results in more heat being produced