Energy-requiring Reactions
Energy-requiring Reactions - Related Videos
01:20
Energy-requiring Steps of Glycolysis
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2019
Glucose is the source of nearly all energy used by organisms. The first step of converting glucose into usable energy is called glycolysis. Glycolysis occurs in the cytosol of the cell over two phases: an energy-requiring phase and an energy-releasing phase. Over the first three steps, glucose is converted into different forms and attached to two phosphate groups donated by two ATP molecules, resulting in an unstable sugar. In the next two stages, the unstable sugar splits into two sugar...
01:16
Cycloaddition Reactions: MO Requirements for Thermal Activation
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2023
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden. The reaction occurs between the highest occupied molecular orbital (HOMO) of one π component and the lowest unoccupied molecular orbital (LUMO) of the other. These are known as...
01:12
Cycloaddition Reactions: MO Requirements for Photochemical Activation
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2023
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden. Thermally-induced [2 + 2] cycloadditions are symmetry forbidden. This is because the ground state HOMO of one ethylene molecule and the LUMO of the other ethylene are out of phase, preventing a concerted suprafacial-suprafacial overlap. Absorption...
01:29
The Reaction Gibbs Energy
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2026
The reaction Gibbs energy (ΔrG) is a crucial parameter that determines whether a reaction will occur spontaneously or not. It can be used to categorize reactions into two types: exergonic and endergonic.Exergonic reactions are those in which ΔrG is less than zero. This implies that these reactions can occur spontaneously without an external input of energy. In biological systems, a typical example of an exergonic reaction is the oxidation of carbohydrates. This reaction produces simple...
01:16
Energy Transfer in Chemical Reactions
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2023
Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine a person building a brick wall. The energy it takes to lift and place one brick on top of another is the kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential...
FAQs
Energy coupling connects an energy-requiring reaction with a favorable reaction so that the energy released by one process drives the other. In cells, ATP hydrolysis commonly provides this linked input, allowing otherwise unfavorable steps to proceed as part of coordinated metabolic pathways. This arrangement supports the construction of cellular components without treating each reaction as an isolated event.
ATP hydrolysis acts as a frequent energy source for cellular work by supplying energy to coupled reactions. The hydrolysis step does not replace the biosynthetic or transport process; instead, its favorable energy change is linked to that process. Cells can therefore use ATP to support molecular assembly and movement against concentration gradients.
Enzymes lower the activation barriers that reactions must overcome and coordinate successive steps in a pathway. They do not serve as the energy input described for an endergonic process, but they help the coupled reactions occur efficiently and in the proper sequence. This coordination is important when cells build complex molecules or maintain organized metabolism.
Active transport moves substances against concentration gradients, so cells must connect the transport step with ATP hydrolysis or another favorable reaction. Coupling supplies the energy needed for movement that would not proceed through the gradient alone. This mechanism helps cells regulate their internal conditions, making it relevant to homeostasis and cellular organization.
During biosynthesis, coupled energy inputs support the assembly of complex molecules and other cellular components. The pathway uses favorable reactions, often ATP hydrolysis, to drive steps that build larger or more organized products. This role connects energy use with growth and repair, because cells must continually produce and maintain their structural and functional materials.
Energy-requiring reactions support several forms of cellular work, including active transport and processes associated with movement, growth, repair, and homeostasis. Their importance lies in linking energy transfer to organized biological activity. Studying these reactions therefore helps explain how organisms capture, distribute, and use energy to maintain living systems over time.