metabolism

• The living cell is a miniature chemical factory where thousands of reactions occur
• The cell extracts energy and applies energy to perform work
• Some organisms even convert energy to light, as in bioluminescence
• Metabolism is the totality of an organism’s chemical reactions
• Metabolism is an emergent property of life that arises from interactions between molecules within the cell
• An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics
• A metabolic pathway begins with a specific molecule and ends with a product
• Catabolic pathways release energy by breaking down complex molecules into simpler compounds
• Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway of catabolism
• Anabolic pathways consume energy to build complex molecules from simpler ones
• The synthesis of protein from amino acids is an example of anabolism
• Bioenergetics is the study of how organisms manage their energy resources
• Energy is the capacity to cause change
• Energy exists in various forms, some of which can perform work
• Kinetic energy is energy associated with motion
• Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules
• Potential energy is energy that matter possesses because of its location or structure
• Energy can be converted from one form to another
• Thermodynamics is the study of energy transformations
• Chemical energy is potential energy available for release in a chemical reaction
• A closed system, such as that approximated by liquid in a thermos, is isolated from its surroundings
• In an open system, energy and matter can be transferred between the system and its surroundings
• Organisms are open systems
• According to the first law of thermodynamics, the energy of the universe is constant
• First Law of Thermodynamics - Energy can be transferred and transformed, but it cannot be created or destroyed
• The first law of thermodynamics is also called the principle of conservation of energy
• Living cells unavoidably convert organized forms of energy to heat
• For a process to occur without energy input, it must increase the entropy of the universe
• Cells create ordered structures from less ordered materials
• Energy flows into an ecosystem in the form of light and exits in the form of heat
• The evolution of more complex organisms does not violate the second law of thermodynamics
• Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases
• The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously
• Biologists want to know which reactions occur spontaneously and which require input of energy. To do so, they need to determine energy changes that occur in chemical reactions
• A living system’s free energy is energy that can do work when temperature and pressure are uniform, as in a living cell
• The change in free energy (∆G) during a process is related to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin (T): ∆G = ∆H – T∆S
• Only processes with a negative ∆G are spontaneous
• Spontaneous processes can be harnessed to perform work
• Free energy is a measure of a system’s instability, its tendency to change to a more stable state
• During a spontaneous change, free energy decreases and the stability of a system increases