How cells convert energy

Cells convert energy

The animal's cells make energy in two ways
  • Substrate-level Phosphorylation.
  • Chemiosmosis.

Substrate-level Phosphorylation


The production of Adenosine Triphosphate by coupling is strongly exergonic reaction with Adenosine Triphosphate synthesis from Adenosine Diphosphate and phosphate is called substrate level-phosphorylation.
  1. ATP formation from ADP and phosphate requires input energy. The chemical reaction is allying with an exergonic reaction. so it releases energy.
  2. An enzyme sends a phosphate group to Adenosine DiPhosphate to synthesize a substrate. So ATP molecule is formed.
  3. The energy synthesizes from the exergonic reaction is significant than the energy input necessary to carry on ATP synthesis. The generation of ATP by coupling is strongly exergonic reaction.

Early evolution of substrate-level-phosphorylation

Substrate level-phosphorylation comes into view very early in the record of organisms.


Following factors support this view:
  1. Organisms in the early stages use carbohydrates as an energy source of origin. Energy eliminates carbohydrates by substrate-level phosphorylation.
  2. The mechanism for substrate level-phosphorylation is present in most living cells.
  3. Substrate level-phosphorylation is one of the most fundamental of all ATP-generating reaction.



The coupling reaction in which synthesis of ATP molecule takes place during the movement of H+ ions across an H+ gradient is known as chemiosmosis.

The substrate level-phosphorylation is the oldest method of generating ATP. But more ATP is generated by a process of chemiosmosis.

Mechanism of Chemiosmis

Organisms carry transmembrane channels in their mitochondrial membranes that pump protons(H+)

  1. Outer movement of the proton by proton pump: These protons pumps use a flow of electrons to induce a shape change in proteins. It causes protons to move out of the inner compartment of mitochondria.
  2. Increase in the concentration of H+ in the outer compartment: As the proton (H+) concentration in the outer compartment of the mitochondria becomes greater than that of the inside compartment.
  3. Electrical chemical proton gradient: The outer protons are pushed across the membrane by an electrical-chemical gradient.
  4. Inward movement of H+: The protons move down the gradient between outer and inner mitochondrial compartments.
  5. Adenosine Triphosphate synthesis: They induce the formation of ATP from ADP, phosphate, and the enzyme ATP synthetase.
  6. Cellular respiration: The electrons that drive the electron transport system involved in chemiosmosis are obtained from chemical bonds of food molecules in all organisms and from photosynthesis in plants. This electron removing process is called cellular respiration. It is also called aerobic respiration. Because the free amount of oxygen is needed. Aerobic respiration is the oxidation of food molecules to get energy.

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