Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions

Flashcards from Concept 8.3 of Pearson's Campbell Biology, Twelfth Edition.

Chemical work

Work that pushes endergonic reactions

Transport work

Work that pumps substances across membranes against the direction of spontaneous movement

Mechanical work

Work such as beating cilia or contracting muscle cells

Energy coupling

The use of an exergonic process to drive an endergonic one to manage energy resources in a cell

• Mediated by ATP in most cells

Adenosine triphosphate (ATP)

Particle composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups

• Functions in energy coupling and as one of the nucleoside triphosphates used to make RNA

• Energy is released when the terminal phosphate bond is broken by hydrolysis (adding water molecules)

Hydrolysis

The addition of a water molecule to break a bond in another molecule

• Used to release energy in ATP by breaking the terminal bond through its chemical change to a state of lower free energy in the products

  • This is an exergonic change to drive later endergonic reactions as well as transport and mechanical work in the cell

Repulsion

A word that describes molecules pushing away from each other in a bond

• Phosphate groups do this in ATP, creating lots of potential energy as in a compressed spring

Phosphorylation

The transfer of a phosphate group from ATP to another molecule typically used to power endergonic reactions

• Seen in ADP gaining a group after exergonic, catabolic reactions

Adenosine diphosphate (ADP)

One of the products after ATP hydrolysis that helps regenerate ATP through the addition of a phosphate molecule

ATP cycle

The shuttling of inorganic phosphate and energy between ATP and ADP that couples energy-yielding processes to energy-consuming ones