Bioenergetics

• BIOLOGY AND ENERGY FLOW

  • Life systems and their activity require energy and facilitate the flow of energy
  • Life needs to be ordered and structured due to to their ability to replicate, this requires energy, which means organisms release heat into the environment
  • Over 160 years ago, a term called energy was discovered, and it was surmised to be conserved
  • E is total internal energy
• THERMODYNAMICS

  • Study of macroscopic states near equilibrium
• Relaxation lifetimes

  • Time it takes for a system with various entities, interactions, and a number of energy states to reach thermal equilibrium
  • Every system differs
  • Long as most are composed of short metabolic processes and structures with long decay time
  • Living systems cannot have thermal equilibrium, there are processes that help us avoid reaching this
• • In physics, 2 bodies in thermal contact that do not exhibit macroscopic transfer of energy have the same temperature
• Changes in temperature can cause change in volumes of certain materials (e.g. mercury thermometer)
• • Gases can also be used in measuring temperature, as changes in the temperature can cause changes in pressure, which can be monitored
• • Temperature is not equivalent to average kinetic energy, this only applies to systems which have no intermolecular interaction such as ideal gases
  • Temperature measures energies from both kinetic and potential energy
• • In temperature, the rate at which internal energy changes per unit change in the disorder of the system, while the volume and particle size of the unit are fixed
• HEAT

  • Energy transferred between two bodies due to a difference in temperature
  • Energy transfer can lead to volume changes within systems
• Heat Transfer

  • Causes a redistribution of the occupation numbers of the possible energy levels in the system without changing the energy levels in the microstates
  • Associated with change in disorder
• • Heat goes into a system (+)
  • When heat is absorbed by a system from its surroundings
  • E.g. When you place a pot of water on a stove, heat from the stove is transferred into the water, causing its temperature to rise
• • Heat goes out of a system (-)
  • When a system releases heat energy to its surroundings
  • E.g. When you turn off the stove and allow the pot of water to cool, heat is transferred from the water to the cooler surroundings
• • Adiabatic process - a change of a system involving no transfer of heat
• 1. Conduction

  • By means of molecular agitation within a material without any motion of the material as a whole
• 1. Convection 

  • By mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it
• 1. Radiation

  • By EM waves such as visible light, UV and infrared radiation
• HOMEOSTASIS

  • We maintain a temperature of 37°C through various means
  • Regulation of blood flow
  • Perspiration
  • Coverings
  • Hair erection
  • Shivering
  • Cell mitochondrial thermogenic control
  • Folding to reduce temperature
  • Exhalation
• • Our brain consumes 25 % of the energy present in blood, by product is heat
• 1. Zeroth Law of Thermodynamics

  • If two thermodynamic systems are in equilibrium with a third, then the two are in equilibrium with each other
• 1. First Law of Thermodynamics

  • The change in internal energy of a system equals to the heat added to the system minus the work done
• 1. Second Law of Thermodynamics

  • The entropy of any natural and spontaneous process either increases or remains constant
• 1. Third Law of Thermodynamics

  • Entropy of a pure crystal is zero as the temperature approaches absolute zero
• ENTROPY

  • A measure of disorder in a system, defined by the second law of thermodynamics
  • The entropy change of a system from state A to state B will never be LESS than the change of entropy of a thermodynamic process that carries it from A to B
• GIBBS FREE ENERGY

  • A value for isothermal and isobaric processes denoting the spontaneity of a system or an event
  • Minimized by systems at equilibrium
  • Applicable for most chemical and biological events
• T or F. Living systems must have thermal equilibrium.

  F. They cannot.