law of Thermodynamics

• Thermodynamics


  The study of energy and energy transfer involving physical matter
• System


  The matter and its environment relevant to a particular case of energy transfer
• Surroundings


  Everything outside the system
• Types of systems


  • Open
  • Closed
• Open system


  Energy and matter can transfer between the system and its surroundings
• Closed system


  Can transfer energy but not matter to its surroundings
• Example of an open system


  • Heating a pot of water on the stove - the system includes the stove, the pot, and the water. Energy transfers within the system (between the stove, pot, and water). This system is open because it can lose heat into the air.
• Biological organisms


  Open systems - energy exchanges between them and their surroundings, as they consume energy-storing molecules and release energy to the environment by doing work
• First law of thermodynamics


  The total amount of energy in the universe is constant. Energy may transfer from place to place or transform into different forms, but it cannot be created or destroyed.
• First law of thermodynamics


  • Energy exists in many different forms
  • Energy transfers and transformations take place around us all the time
• Challenge for living organisms


  Obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work
• How living cells obtain usable energy


  1. Chemical energy stored within organic molecules such as sugars and fats transforms through a series of cellular chemical reactions into energy within ATP molecules

  2. Energy in ATP molecules is easily accessible to do work
• Types of work cells need to do


  • Building complex molecules
  • Transporting materials
  • Powering the beating motion of cilia or flagella
  • Contracting muscle fibers to create movement
  • Reproduction
• Second law of thermodynamics

  None of the energy transfers are completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable, usually heat energy.
• Heat energy


  Energy that transfers from one system to another that is not doing work
• Example of heat energy loss


  • When an airplane flies through the air, it loses some of its energy as heat energy due to friction with the surrounding air. This friction actually heats the air by temporarily increasing air molecule speed.
• Some energy is lost as heat energy during cellular metabolic reactions
• Heat energy helps to maintain our body temperature
• Entropy


  The more energy that a system loses to its surroundings, the less ordered and more random the system. High entropy means high disorder and low energy.
• Example of high entropy


  • A student's bedroom. If no energy or work were put into it, the room would quickly become a messy, very disordered state, one of high entropy. Energy must be put into the system, in the form of the student doing work and putting everything away, in order to bring the room back to a state of cleanliness and order. This state is one of low entropy.
• Molecules and chemical reactions have varying amounts of entropy
• As chemical reactions reach a state of equilibrium, entropy increases, and as molecules at a high concentration in one place diffuse and spread out, entropy also increases
• Living things


  Highly ordered, requiring constant energy input to maintain themselves in a state of low entropy. As living systems take in energy-storing molecules and transform them through chemical reactions, they lose some amount of usable energy in the process, because no reaction is completely efficient. They also produce waste and by-products that are not useful energy sources. This process increases the entropy of the system's surroundings.
• Since all energy transfers result in losing some usable energy, the second law of thermodynamics states that every energy transfer or transformation increases the universe's entropy
• Even though living things are highly ordered and maintain a state of low entropy, the universe's entropy in total is constantly increasing due to losing usable energy with each energy transfer that occurs
• Living things are in a continuous uphill battle against this constant increase in universal entropy