Study Notes on Adenosine Triphosphate (ATP)

Adenosine Triphosphate (ATP)

Definition of ATP
- Adenosine triphosphate (ATP) is known as the energy currency of all life on Earth.
- Represented often with a yellow starburst to symbolize its energy content.

Components of ATP
- Adenine:
- A purine and nitrogenous base consisting of carbon (black) and nitrogen (blue).
- Found in the rungs of DNA.
- Ribose Sugar:
- A five-carbon sugar that forms part of the ATP structure.
- Phosphate Groups:
- ATP contains three phosphate groups.
- Phosphorus is surrounded by oxygen.

Formation of ATP from Adenosine
- Adenine and ribose combine to form adenosine.
- Adding a phosphate yields adenosine monophosphate (AMP).
- Adding another phosphate creates adenosine diphosphate (ADP).
- Adding a third phosphate results in adenosine triphosphate (ATP).

Phosphate Bonds:
- The bond between the last two phosphate groups is analogous to a spring.
- Storing energy when the bond is formed; the bond holds potential energy.
Hydrolysis of ATP:
- Reacts with water to release energy, breaking down into ADP.
- In the hydrolysis reaction, an OH group binds one side and an H binds the other side.
- This process is called hydrolysis or "breaking with water".
- Free phosphate (Pi) released has a specific amount of potential energy.
Recharging ATP:
- ATP can be regenerated by attaching a phosphate to ADP in a dehydration reaction.

Cellular Respiration:
- ATP is produced inside mitochondria, primarily facilitated by the enzyme ATP synthase.
- A proton gradient is built, with protons flowing through ATP synthase, synthesizing ATP.
Movement and Distribution:
- ADP and inorganic phosphate (Pi) concentrations are lowest in regions where ATP is formed, and ATP flows to areas of low concentration.
- Once used, ATP converts back into ADP and Pi, re-entering the mitochondria for reuse.

Photosynthesis:
- Plants produce ATP on the thylakoid membrane of chloroplasts using light energy.
- The process is distinct from mitochondrial ATP production because it uses light energy to create ATP.
- ATP produced is utilized in the Calvin Cycle to synthesize sugars.
Mitochondrial Functions:
- Plants also possess mitochondria to metabolize sugars into ATP.

Active Transport:
- The sodium-potassium pump is a primary example of ATP use for active transport in cells, especially neurons.
- ATP donates a phosphate group to the pump, moving three sodium ions out and two potassium ions in.
- Approximately 20% of the body's energy is used for this pump, essential for nerve function.
Muscle Contraction:
- ATP binds to the protein myosin, enabling muscle contraction via interaction with actin.
Polymer Formation:
- In protein synthesis, ATP contributes to the attachment of amino acids on tRNA for ribosome activity.
- ATP is a crucial molecule in building RNA and proteins.

LUCA (Last Universal Common Ancestor):
- ATP has existed since the appearance of LUCA, the common ancestor to all life forms.
- LUCA used ATP, RNA, and DNA, along with proteins, membranes, and ion channels.
Homology with Nucleotides:
- RNA contains adenine and ribose, resembling ATP with a single phosphate.
- ATP is integral in synthesizing RNA, emphasizing its dual role.
- Structure of DNA also has adenine, further linking ATP to cellular functions.

Prevalence of ATP:
- ATP is fundamental across all life forms, serving dual roles in energy transfer and molecular construction.
- ATP production involves simple processes of energy storage and release crucial for cellular metabolism.
- The concept of ATP persists throughout biological systems, symbolizing continuity from ancient life forms to present-day organisms.