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Potential energy is not only associated with the location of matter (such as a child sitting on a tree branch), but also with the structure of matter. A spring on the ground has potential energy if it is compressed; so does a rubber band that is pulled taut. The very existence of living cells relies heavily on structural potential energy. On a chemical level, the bonds that hold the atoms of molecules together have potential energy. Remember that anabolic cellular pathways require energy to synthesize complex molecules from simpler ones, and catabolic pathways release energy when complex molecules are broken down. The fact that energy can be released by the breakdown of certain chemical bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the bonds of all the food molecules we eat, which is eventually harnessed for use. This is because these bonds can release energy when broken. The type of potential energy that exists within chemical bonds, and is released when those bonds are broken, is called chemical energy    ( [link] ). Chemical energy is responsible for providing living cells with energy from food. The release of energy is brought about by breaking the molecular bonds within fuel molecules.

The molecular formula of octane (top), which is a chain of eight carbons and eighteen hydrogens, fuels a racecar speeding along a track (bottom).
The molecules in gasoline (octane, the chemical formula shown) contain chemical energy within the chemical bonds. This energy is transformed into kinetic energy that allows a car to race on a racetrack. (credit “car”: modification of work by Russell Trow)

Visit this site and select “A simple pendulum” on the menu (under “Harmonic Motion”) to see the shifting kinetic (K) and potential energy (U) of a pendulum in motion.

Free energy

After learning that chemical reactions release energy when energy-storing bonds are broken, an important next question is how is the energy associated with chemical reactions quantified and expressed? How can the energy released from one reaction be compared to that of another reaction? A measurement of free energy    is used to quantitate these energy transfers. Free energy is called Gibbs free energy (abbreviated with the letter G) after Josiah Willard Gibbs, the scientist who developed the measurement. Recall that according to the second law of thermodynamics, all energy transfers involve the loss of some amount of energy in an unusable form such as heat, resulting in entropy. Gibbs free energy specifically refers to the energy associated with a chemical reaction that is available after entropy is accounted for. In other words, Gibbs free energy is usable energy, or energy that is available to do work.

Every chemical reaction involves a change in free energy, called delta G (∆G). The change in free energy can be calculated for any system that undergoes such a change, such as a chemical reaction. To calculate ∆G, subtract the amount of energy lost to entropy (denoted as ∆S) from the total energy change of the system. This total energy change in the system is called enthalpy    and is denoted as ∆H . The formula for calculating ∆G is as follows, where the symbol T refers to absolute temperature in Kelvin (degrees Celsius + 273):

Questions & Answers

prove starch in a mango leaf
Ruth Reply
prove starch in a leaf
Ruth
draw and name the plant cell
Nalongo
wat is classification
Nalongo
levels of classification
Nalongo
classification of what
Ezenwa
Nidhipal
Nidhi
Identify the caste of termites or Honey bees
Mensah Reply
Soldier Winged reproductive Worker King and queen
Franklina
what is biology
Jackson Reply
biology is a study of living organism
Brilliant
what is the myelin sheath?
description on how an enzyme such as pepsin breaks down a substrate
linister Reply
what is biology
Kanzy Reply
study of life
Tufail
the study of life..meaning studying all aspects of life in humans,animals and everything inside the global
Nalukui
study of life
Memory
is the branch of science which deal with the study of living and non living things
David
Is the study of living organisms or living things
Franklina
draw the taxonomic hierarchy of classification
KC Reply
Kingdom Class Order Family Genus Species
Franklina
explain the following bush burning, deforestation, over grazing
Thomas Reply
what is biodiversity
Tracy
No idea
nana
Please what are alleles
nana
Deforestation: this is the cutting down of trees without planting new ones
Brilliant
over grazing is the continuously planting of crops in one particular land.
Friday
what is afforestation
Friday
Bush burning is the removal of the natural vegetation cover, that protects the soil surface through the use of fire. Deforestation is the actor process of establishing a forest especially on land not previously forested.
Franklina
Over grazing is the practice of grazing toi many livestock for too long a period on a land unable to recover its vegetation.
Franklina
what is physiology
Joseph Reply
the study of physical things
Nalukui
dealing with those things which you can see by your neck eyes
Odwa
Further explanation please
nana
the study of things tt interact with time,energy
David
Is the scientific study of chemistry and physics of the structure of the body
Franklina
can a lactating mother get pregnant
Elias Reply
what is cell
Deng Reply
the basic building blocks of all living matter...
Izzati
cell is a basic unit of life
MAI
building blocks ie cells not a cell there4 a cell is the basic unit of biotic things
David
Cell is a basic unit of life
Malekhotla
A cell is the basic structural and functional unit of life
Franklina
A cell is the basic unit of life,it include both plant and animals need a cell
Thomas
what's microscope
Emmanuel Reply
is any instrument that use to wiew or to see the small object that you can't see with our naked eye
MR
is any instrument used to magnifie small object
Memory
Is an instrument that produces an enlarged image of an object or specimen that is too small to be seen with our naked eye
Franklina
what is the function of the spinal cord
Gaone Reply
For responsible of movement and sensation
Franklina
A cell is the structural and fictional unit of life
Evelyn Reply
what is tidal volume
Erick
tidal volume is the volume of each breath measured during inspiration or expiration or averged for the entire respiratory cycle
Gaone
Give function of the long strands of slippery or jelly like substance in eggs of the amphibians in water ?
Erick
the long strands of slippery or jelly like substance him eggs of amphibians in water helps in keeping the eggs moist and protection from predators
Gaone
sorry not him in
Gaone
what's is microscope
Emmanuel
How do bacteria useful?
Bisirikirwa
how can plant feed other animals
Nana Reply
After the animals has death and decayed then the plant used the nutrients to manufacture there food.
Yusuf
Plants and animals depends on each other. Meaning, plants help animals with greens and fruits or vegetables while animals provides nutrients when dead and decayed. Therefore,as you see the food web and food chain, you'll have more.
Jairenaririko

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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