Difference Between ATP and ADP

Introduction image

Difference between ATP and ADP is mainly due to the given three factors like their energy state, a number of phosphate groups and the hydrolysis process.
Energy state: ATP is comparatively high energy molecule than ADP.
Phosphate group: There are three phosphate group in ATP, while two in ADP.
Hydrolysis: As a result of hydrolysis, ATP hydrolyzes into ADP, which in turn hydrolyze into AMP.

Both the ATP and ADP molecules are the two universal power source that mediates various biological or cellular functions.

Content: ATP Vs ADP

  1. Comparison Chart
  2. Definition
  3. Examples
  4. Key Differences
  5. Similarities
  6. Conclusion

Comparison Chart

PropertiesATPADP
Full formAdenosine tri-phosphateAdenosine di-phosphate
Common nameAdenosine 5’-triphosphateAdenosine 5’-diphosphate
Alternative nameIt has no such alternative namesAdenosine pyrophosphate
Molecular formulaC10H16N5O13P3C10H15N5O10P2
Molar mass507.18 g/mol427.2 g/mol
FormulationSolidCrystalline solid
Number of phosphate groupsThreeTwo
Form ofPotential energyKinetic energy
Energy stateHigherComparatively lower
StabilityRelatively unstableComparatively stable
Hydrolytic reactionThe reaction of ATP with water causes the formation of ADP and release of energy by the removal of one phosphate groupThe reaction of ADP with water causes the formation of AMP and release of energy by the removal of one more phosphate group
Conversion reactionEndergonic reaction Exergonic reaction
FunctionsHelps in active transport, building of molecules, cellular functions like muscle movement etc.Helps in catabolism reactions, in the activation of platelets etc.

Definition

ATP: It is an acronym for the term “Adenosine tri-phosphate” which can define as the high energy organic biomolecule to drive many biological processes by donating its high energy phosphate molecule. The structure of adenosine tri-phosphate includes three distinct groups, namely adenine (nucleotide base), ribose (pentose sugar) and triphosphate (phosphoryl group).

The active form of adenosine tri-phosphate contains a combination of ATP molecules with Mg2+ or Mn2+ ions. It can consider as the energy process of all life forms, which fuel different cells to carry out specific functions. ATP mediates intracellular energy transfer.

Structure

Adenine: It is the nitrogenous base, whose 9th nitrogen atom attaches with the 1st carbon-atom of the ribose sugar.
Ribose sugar: It is the pentose sugar that is located intermediary between the adenine and phosphoryl group.
Phosphate: The phosphoryl group fixes to the 5th carbon atom of the ribose sugar. These are three in number, comprised of α, β and γ terminal phosphate linked via phosphodiester bond, followed by two phosphoanhydride bonds.

Structure of ATP and ADP

ADP: It is an acronym for the term “Adenosine di-phosphate” which can define as comparatively low energy organic biomolecule to mediate energy flow by donating its high energy phosphate molecule. The structure of Adenosine di-phosphate includes three distinct groups, namely adenine (nucleotide base), ribose (pentose sugar) and diphosphate (phosphoryl group). ADP also mediates the intracellular energy flow.

Structure

Adenine: It is the nitrogenous base, whose 9th nitrogen atom is attached with the 1st carbon-atom of the ribose sugar.
Ribose sugar: It is the pentose sugar that is found intermediary between the adenine and phosphoryl group.
Phosphate: The phosphoryl group is joined to the 5th carbon atom of the ribose sugar. These are two in number, comprised of only α and β phosphate group linked via phosphodiester bond, followed by one phosphoanhydride bond.

Examples

The concept of ATP and ADP can be understood by taking the following references:

  • ATP can be considered as a fully charged battery. When the power of the battery reduces, it indicates the loss of energy. Hence the reduced form of energy or partially charged battery will consider as ADP.
  • If we have to buy a product, we must need a source of capital or cash. Similarly, a cell must need a particular source of energy to perform specific tasks. So let us suppose ATP as a bank check, so to purchase a product we need to convert the check amount into cash. Therefore, a cell also converts ATP into ADP and energy to do various cellular functions.

Key Differences Between ATP and ADP

  1. The molecular formula of ATP is C10H16N5O13P3. As a result of hydrolysis one hydrogen, two oxygen and one phosphate group eliminate from the ATP, and the molecular formula of ADP will represent as C10H15N5O10P2.
  2. One of the common distinguishing features between ATP and ADP is the number of the phosphate group present. There are three phosphate groups in ATP and two in ADP.
  3. ATP can consider as the potential energy which is basically stored energy that can be used by a cell to do particular tasks. ADP can consider as the kinetic energy which is necessary for the flow of energy.
  4. The hydrolysis of ATP and ADP causes the formation of ADP and AMP, respectively and the release of free energy by the removal of one phosphate group.
  5. The process of ATP formation from ADP is an endergonic reaction (the energy is absorbed), whereas the process of ADP formation from ATP is an exergonic reaction (the energy is released).
  6. Functions of ATP promotes active transport, the building of molecules, cellular functions like muscle movement etc.  While ADP helps in catabolic reactions, activation of platelets etc.

Similarities

Despite many differences, they also share some common features like:

  • Both ATP and ADP are the energy molecules that can drive cellular functions.
  • Their structure is common by having adenine base, a ribose sugar and a phosphate group.
  • Both are constantly interconverted and regenerated inside a body.

Conclusion

We can conclude that a cell needs both adenosine triphosphate and adenosine diphosphate as a source of energy to drive many cellular functions like respiration, digestion, muscle movement etc. Therefore there must be a constant interconversion and regeneration of ATP to fulfil the energy requirement through ATPase enzymatic activity and cellular respiration, respectively.

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