Multiple Choice
In cell biology, which activated carrier molecule most directly provides the energy to fuel many forms of active transport across membranes?
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3. Energy
Activated Carriers
Multiple Choice
In the context of activated carriers, how does ATP most directly provide energy to a cell to drive an otherwise unfavorable reaction?
A
By increasing the cell temperature through heat release so that endergonic reactions become spontaneous
B
By storing energy primarily as high-energy electrons that are donated directly to oxygen in the cytosol
C
By transferring a phosphate group to a substrate (phosphorylation), which couples ATP hydrolysis to the reaction and lowers the overall free-energy change
D
By binding to enzymes as a permanent prosthetic group that remains attached after the reaction is complete
Verified step by step guidance1
Understand that ATP (adenosine triphosphate) acts as an activated carrier by storing and transferring energy within the cell.
Recognize that ATP contains high-energy phosphate bonds, especially the bond between the terminal phosphate groups, which can be broken through hydrolysis.
Know that ATP hydrolysis releases energy by converting ATP to ADP (adenosine diphosphate) and an inorganic phosphate (Pi), and this energy can be used to drive unfavorable reactions.
Learn that the most direct way ATP provides energy is by transferring a phosphate group to a substrate molecule, a process called phosphorylation, which changes the substrate's energy state and makes the coupled reaction more favorable.
Realize that this coupling of ATP hydrolysis to the reaction lowers the overall free-energy change (ΔG), allowing endergonic reactions to proceed spontaneously.
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