The Flow of Energy In Living Systems Unit 3: Bioenergetics Honors Biology Monkemeier

Thermodynamics  Thermodynamics is the branch of science that relates to energy changes (conversions from one form to another)  The Laws of Thermodynamics help to explain energy and energy changes.

Bioenergetics  Bioenergetics is the field of biochemistry that concerns energy flow through living systems.  All activities of living organisms involve flow of energy through living systems as well as changes in energy.

What is Energy?  Energy is defined as the capacity to do work.  We think of energy as existing in two states: Kinetic energy and potential energy.

Energy  Kinetic energy is energy of motion. Moving objects perform work by causing other matter to move.  Potential energy is stored energy. Objects that are not moving but have the capacity to do so posses potential energy.

The Many Forms of Energy  Energy can take many forms: mechanical energy (kinetic and potential), heat, sound, electric current, light, or radioactive radiation.

Heat  Because it can exist in so many forms, energy can be measured in many ways.  The most convenient measure is in terms of heat, because ALL other forms of energy can be converted into heat.  The term THERMODYNAMICS means “heat changes”.

Measuring HEAT (Energy)  The unit of heat most commonly employed in biological systems is the kilocalorie (kcal)  1 kcal = 1,000 calories  1 calorie = the amount of heat required to raise 1 gram of water one degree Celsius  Another unit that can be used is the joule. It takes 4.18 joules of energy to raise 1 gram of water one degree Celsius.

Organisms  Organisms require a constant supply of energy.  The ultimate source of energy for living systems is the SUN!

Photosynthesis  Autotrophs (Producers) use the process of photosynthesis to convert radiant electromagnetic energy into chemical energy.  Photosynthesis converts carbon from an inorganic form (CO 2 ) to an organic form, in the process of storing energy from the SUN as potential energy in the covalent bonds between atoms of sugar molecules.

Oxidation – Reduction Reactions  Energy flows through living systems (organisms) as a series of oxidation and reduction reactions.  High energy electrons are stripped from one molecule (oxidizing it) and given to another molecule (reducing it).  Oxidation – reduction reactions ALWAYS occur together.  Oxidation – reduction reactions (REDOX reactions) play a key role in the flow of energy through biological systems.

Oxidation / Reduction

Putting it all Together!  Photosynthesis converts radiant electromagnetic energy into chemical energy.  Chemical energy is energy between the atoms of a molecule.  Cellular respiration is the process that converts chemical energy into free energy.  Free energy is energy that is available to do work immediately.  Free Energy is stored and released in a molecule of ATP.

Photosynthesis and Cellular Respiration

Bioenergetics and Thermodynamics  Bioenergetics studies the flow of energy through living systems (organisms).  As energy flows through living systems and is converted from one form to another, it is governed by the Laws of Thermodynamics.  The next PPT will relate to the Laws of Thermodynamics.

Next PPT  The Laws of Thermodynamics