potential energy

Examples of potential energy in the following topics:

• Types of Energy

  • The various types of energy include kinetic, potential, and chemical energy.
  • The jet engines are converting potential energy in fuel to the kinetic energy of movement.
  • Objects transfer their energy between potential and kinetic states.
  • This type of potential energy is called chemical energy, and like all potential energy, it can be used to do work.
  • Water behind a dam has potential energy.

• Water and Solute Potential

  • Water potential is the measure of potential energy in water and drives the movement of water through plants.
  • Water potential is a measure of the potential energy in water, or the difference in potential energy between a given water sample and pure water (at atmospheric pressure and ambient temperature).
  • The potential of pure water (Ψwpure H2O) is designated a value of zero (even though pure water contains plenty of potential energy, that energy is ignored).
  • Solutes reduce water potential (resulting in a negative Ψw) by consuming some of the potential energy available in the water.
  • In other words, the amount of available potential energy is reduced when solutes are added to an aqueous system.

• Electrons and Energy

  • The removal of an electron from a molecule via a process called oxidation results in a decrease in the potential energy stored in the oxidized compound.
  • The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound).
  • The transfer of electrons between molecules via oxidation and reduction is important because most of the energy stored in atoms is in the form of high-energy electrons; it is this energy that is used to fuel cellular functions.
  • The transfer of energy in the form of electrons allows the cell to transfer and use energy in an incremental fashion: in small packages rather than as a single, destructive burst.
  • Describe the role played by electrons in energy production and storage

• Pressure, Gravity, and Matric Potential

  • Pressure potential may be positive or negative; the higher the pressure, the greater potential energy in a system, and vice versa.
  • Without height, there is no potential energy in the system.
  • The force of gravity pulls water downwards to the soil, which reduces the total amount of potential energy in the water in the plant (Ψtotal).
  • The binding of water to a matrix always removes or consumes potential energy from the system.
  • Ψm is similar to solute potential because the hydrogen bonds remove energy from the total system.

• Secondary Active Transport

  • While this process still consumes ATP to generate that gradient, the energy is not directly used to move the molecule across the membrane, hence it is known as secondary active transport.
  • This secondary process is also used to store high-energy hydrogen ions in the mitochondria of plant and animal cells for the production of ATP.
  • The potential energy that accumulates in the stored hydrogen ions is translated into kinetic energy as the ions surge through the channel protein ATP synthase, and that energy is used to convert ADP into ATP.

• The Energy-Releasing Steps of Glycolysis

  • In the second half of glycolysis, energy is released in the form of 4 ATP molecules and 2 NADH molecules.
  • Both of these molecules will proceed through the second half of the pathway where sufficient energy will be extracted to pay back the two ATP molecules used as an initial investment while also producing a profit for the cell of two additional ATP molecules and two even higher-energy NADH molecules .
  • The sixth step in glycolysis oxidizes the sugar (glyceraldehyde-3-phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH.
  • Here, again, there is a potential limiting factor for this pathway.
  • This enzyme causes 2-phosphoglycerate to lose water from its structure; this is a dehydration reaction, resulting in the formation of a double bond that increases the potential energy in the remaining phosphate bond and produces phosphoenolpyruvate (PEP).

• ATP: Adenosine Triphosphate

  • ATP provides the energy for both energy-consuming endergonic reactions and energy-releasing exergonic reactions, which require a small input of activation energy.
  • The more bonds in a molecule, the more potential energy it contains.
  • Since ATP hydrolysis releases energy, ATP synthesis must require an input of free energy.
  • To harness the energy within the bonds of ATP, cells use a strategy called energy coupling.
  • For example, transmembrane ion pumps in nerve cells use the energy from ATP to pump ions across the cell membrane and generate an action potential.

• Nerve Impulse Transmission within a Neuron: Action Potential

  • The action potential travels down the neuron as Na+ channels open.
  • Action potentials are considered an "all-or nothing" event.
  • The diffusion of K+ out of the cell hyperpolarizes the cell, making the membrane potential more negative than the cell's normal resting potential.
  • At this point, the sodium channels return to their resting state, ready to open again if the membrane potential again exceeds the threshold potential.
  • Nodes of Ranvier also save energy for the neuron since the channels only need to be present at the nodes and not along the entire axon.

• Life History Patterns and Energy Budgets

  • Plants, for example, acquire energy from the sun via photosynthesis, but must expend this energy to grow, maintain health, and produce energy-rich seeds to produce the next generation.
  • Thus, all species have an energy budget in which they must balance energy intake with their use of energy for metabolism, reproduction, parental care, and energy storage, as when bears build up body fat for winter hibernation.
  • Fecundity is the potential reproductive capacity of an individual within a population.
  • Most of their energy budget is used to produce many tiny offspring.
  • It is a matter of where the energy is used: for large numbers of seeds or for fewer seeds with more energy.

• Nerve Impulse Transmission within a Neuron: Resting Potential

  • The resting potential of a neuron is controlled by the difference in total charge between the inside and outside of the cell.
  • For quiescent cells, the relatively-static membrane potential is known as the resting membrane potential.
  • The resting membrane potential is at equilibrium since it relies on the constant expenditure of energy for its maintenance.
  • As potassium is also the ion with the most-negative equilibrium potential, usually the resting potential can be no more negative than the potassium equilibrium potential.
  • At the peak action potential, K+ channels open and the cell becomes (c) hyperpolarized.