LIFESCI 7A Lecture Notes - Lecture 3: Chemical Energy, Potential Energy, Chemotroph
6.1: An Overview of Metabolism
○ organisms have two ways of harvesting energy from their environment and two sources of
carbon (chem compounds): four principal ways in which organisms acquire the energy and
materials needed to grow, function, and reproduce
● Organisms can be classified according to their energy and carbon sources
○ phototroph An organism that captures energy from sunlight. (ex: plants)
○ chemotroph An organism that derives its energy directly from organic molecules such as
glucose. (ex: Animals)
○ autotroph Any organism that is able to convert carbon dioxide into glucose, thus providing its
own organic source of carbon. (ex: Plants)
○ heterotroph An organism that obtains its carbon from organic molecules synthesized by other
organisms. (ex: Animals)
● Metabolism is the set of chemical reactions that sustain life.
○ metabolism The chemical reactions occurring within cells that convert molecules into other
molecules and transfer energy in living organisms.
■ Chemical reactions that include building/breaking down sugars (like glucose) and
harnessing/release of energy in the process
■ catabolism The set of chemical reactions that break down molecules into smaller units
and, in the process, produces ATP to meet the energy needs of the cell. (breaking down
carbs to sugars)
■ anabolism The set of chemical reactions that build molecules from smaller units utilizing
an input of energy, usually in the form of ATP. Anabolic reactions result in net energy
storage within cells and the organism. (building carbs from sugars)
6.2: Kinetic and Potential Energy
○ Energy: The capacity to do work; a property of objects that can be transferred from one object
to another, and that cannot be created or destroyed
● Kinetic energy and potential energy are two forms of energy
○ kinetic energy The energy of motion.
○ potential energy Stored energy that is released by a change in an object’s structure or
position.; objects naturally move from high potential energy to low
● Chemical energy is a form of potential energy
○ chemical energy A form of potential energy held in the chemical bonds between pairs of atoms
in a molecule.
■ Energy is released when a bond is formed and is absorbed when a bond is broken
■ Strong bonds=low chemical (potential) energy; weak bonds=high chemical (potential
energy)
● Strong bonds do not require a lot of energy to stay together because they are so
stable; weak ones do
● Organic molecules strong source of chemical energy because of weak covalent
bonds, C-C and C-H
● ATP is a readily accessible form of cellular energy
○ High chemical energy in phosphate bonds, energy released when ATP phosporolates into ADP
■ In the body, negative phosphates repel eachother, giving ATP high energy
6.3: The Laws of Thermodynamics
● The first law of thermodynamics: Energy is conserved
○ first law of thermodynamics The law of conservation of energy: Energy can neither be created
nor destroyed—it can only be transformed from one form into another.
■ Ex: energy can be converted from potential energy to kinetic energy
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Document Summary
Organisms have two ways of harvesting energy from their environment and two sources of carbon (chem compounds): four principal ways in which organisms acquire the energy and materials needed to grow, function, and reproduce. Organisms can be classified according to their energy and carbon sources. Phototroph an organism that captures energy from sunlight. (ex: plants) Chemotroph an organism that derives its energy directly from organic molecules such as glucose. (ex: animals) Autotroph any organism that is able to convert carbon dioxide into glucose, thus providing its own organic source of carbon. (ex: plants) Heterotroph an organism that obtains its carbon from organic molecules synthesized by other organisms. (ex: animals) Metabolism is the set of chemical reactions that sustain life. Metabolism the chemical reactions occurring within cells that convert molecules into other molecules and transfer energy in living organisms. Chemical reactions that include building/breaking down sugars (like glucose) and harnessing/release of energy in the process.
