Basics of Metabolism

• Metabolism


  the sum of all chemical reactions that occur in an organism (e.g. digestion)

  
• What can change metabolism rate?

  your age (slows down metabolism), intermittent fasting (improves metabolism)
• What is part of metabolism?

  converting molecules into energy or lipids (stored/potential energy) and breaking down macromolecules and building new molecules
• Metabolic pathways


  step-by-step processes of chemical reactions in the cell

  
• What happens during metabolic pathways?

  the substrates are turned into products and these products become substrates for the next reaction in the process
• Does breaking bonds require or release energy?

  requires energy
• Why does breaking bonds require energy?

  because in order to overcome the bonds between molecules, a certain amount of energy needs to be put in for the molecule to break into separate atoms
• Does forming bonds require or release energy?

  releases energy
• Why does forming bonds release energy?

  to minimize repulsion between atoms to attract new bonds between the atoms
• What is anabolism?

  using energy to form large molecules from small ones (e.g. forming sucrose from glucose and fructose)

  
• Why is anabolism endergonic?

  it takes more energy to break smaller molecules than it takes to form bonds
• What is catabolism?

  the breakdown of complex molecules into simpler molecules, releasing energy (e.g. polypeptide breaks down into amino acid)

  
• Why is catabolism exergonic?

  because different bonds are formed in the process as the bond breaks (e.g. in the combustion of sucrose, the C-C bonds break to form C=O bonds)
• Energy


  the capacity do to work

  
• What are the main types of energy?

  kinetic, potential, thermal, and chemical

  
• Kinetic energy


  energy of motion (e.g. movement of muscles)

  
• Potential energy


  stored energy (e.g. when muscles aren't moving)

  
• Thermal energy

  sum of kinetic and potential energy of matter that make up an object (transferred as heat)

  
• Chemical energy

  potential energy stored in chemical bonds (e.g. food)
• Bond energy


  amount of energy required to make or break a bond
• What happens to energy when bonds are formed?

  energy is released

  
• What happens during the combustion of methane? (CH4 + 2O2 -> CO2 + 2H2O)


  use bond energy to break CH4 and O2 bonds (4 C-H, 2 O=O) and products are rearranged as energy is released when CO2 and H2O are formed (2 C=O, 4 O-H)
• What is the equation for net energy change?

  reactants-products=net energy change
• What does it mean when the net energy change is negative?

  reaction is exergonic (energy released)
• What does it mean when the net energy change is positive?

  reaction is endergonic (energy absorbed)
• Thermodynamics


  study of energy transformations that apply to a system and its surroundings

  
• System

  a cell, organism, substrates and products - what is being studied
• Surroundings


  everything outside the system; the rest of the universe
• Two types of systems

  open and closed
• Open system


  system in which both matter and energy can go in and out

  
• Closed system


  system in which only energy can go in and out

  
• First law of thermodynamics

  energy cannot be created or destroyed, only transformed into another form or transferred to another object

  
• Example of the first law of thermodynamics

  chemical energy from food can be transformed into mechanical energy (muscle movement) and heat
• Second law of thermodynamics

  During every energy transfer or transformation, some energy is unusable, and is often lost as heat, causing an increase in disorder (applies to closed systems)

  
• Entropy


  a measure of disorder

  
• Why is disorder more likely than order?

  because it takes energy to create order in a system, so disorder can happen spontaneously as no energy is required to create disorder
• Free energy


  the chemical energy available to do work

  
• Why do reactions cause a change in free energy?

  because energy is needed to break bonds, chemical reactions break bonds in reactants and form new bonds to make the products
• Endergonic reactions


  reactions that require energy input

  
• Properties of endergonic reactions

  - products contain more free energy than reactants

  - bond energy is higher, so disorder of the system is lower

  - happen non-spontaneously due to the need for energy input

  - change in energy greater than 0