Bioenergetics I
Thermodynamics
Living Organisms Exist in a Dynamic Steady State
• Steady state: living cells or organism maintain a relatively constant
composition different from their constantly changing surroundings.
• Dynamic: although composition is constant, constituents (small
molecules, macromolecules, and supermolecular complexes) are
continuously synthesized and broken down in chemical reactions
that involve a constant flux of mass and energy through the system
• Living organisms exist in a dynamic “steady state”, never
at“equilibrium” with their surroundings
• When a cell can no longer generate energy, it dies and begins to decay
toward equilibrium with its surroundings.
Living Systems are Open Systems
• Living organisms are open systems: exchange energy and matter with
surroundings
Universe = system + surroundings
Life Needs Energy
Living organisms derive energy from their surroundings in two ways:
(1) Sunlight
(2) Chemical fuels (such as glucose
, Photosynthetic cells: release electrons from water and pass them to CO2
producing O2 and carbohydrates (Autotrophs).
Non-photosynthetic cells(Heterotrophs): organisms obtain energy by
oxidizing the energy-rich products by passing their electrons to O2
producing water and CO
Bioenergetics and Thermodynamics
• Bioenergetics is the study of the transformation and use of energy by
living cells.
• Living cells interconvert different forms of energy and also exchange
energy with their surroundings.
• Many observations on the interconversion of different energy forms
led to the formulation of two fundamental laws of thermodynamics.
• Biological energy transformations obey the laws of thermodynamics
The First Law of Thermodynamics
• The total amount of energy in the universe remains constant
(conservation of energy).
• Energy cannot be created or destroyed; it can only change from one
form to another.
• For example, chemical energy available in fuel such as glucose is
converted to the chemical energy of ATP. In skeletal muscle, energy ATP
is convened to mechanical energy during muscle contraction.
• During each conversion, some of the energy dissipates into the
Thermodynamics
Living Organisms Exist in a Dynamic Steady State
• Steady state: living cells or organism maintain a relatively constant
composition different from their constantly changing surroundings.
• Dynamic: although composition is constant, constituents (small
molecules, macromolecules, and supermolecular complexes) are
continuously synthesized and broken down in chemical reactions
that involve a constant flux of mass and energy through the system
• Living organisms exist in a dynamic “steady state”, never
at“equilibrium” with their surroundings
• When a cell can no longer generate energy, it dies and begins to decay
toward equilibrium with its surroundings.
Living Systems are Open Systems
• Living organisms are open systems: exchange energy and matter with
surroundings
Universe = system + surroundings
Life Needs Energy
Living organisms derive energy from their surroundings in two ways:
(1) Sunlight
(2) Chemical fuels (such as glucose
, Photosynthetic cells: release electrons from water and pass them to CO2
producing O2 and carbohydrates (Autotrophs).
Non-photosynthetic cells(Heterotrophs): organisms obtain energy by
oxidizing the energy-rich products by passing their electrons to O2
producing water and CO
Bioenergetics and Thermodynamics
• Bioenergetics is the study of the transformation and use of energy by
living cells.
• Living cells interconvert different forms of energy and also exchange
energy with their surroundings.
• Many observations on the interconversion of different energy forms
led to the formulation of two fundamental laws of thermodynamics.
• Biological energy transformations obey the laws of thermodynamics
The First Law of Thermodynamics
• The total amount of energy in the universe remains constant
(conservation of energy).
• Energy cannot be created or destroyed; it can only change from one
form to another.
• For example, chemical energy available in fuel such as glucose is
converted to the chemical energy of ATP. In skeletal muscle, energy ATP
is convened to mechanical energy during muscle contraction.
• During each conversion, some of the energy dissipates into the
