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Chapter 23

BI110 Chapter Notes - Chapter 23: Atp Hydrolysis, Exergonic Reaction, Adenosine Triphosphate

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Matthew Smith

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Module 23: ATP and Cellular Work
Clicker Question: catabolism is to anabolism, as _____ is to _____
Exergonic; endergonic
Adenosine triphosphate (ATP) is the most widely used energy storage molecule among
organisms. ATP components: nitrogenous base (adenine), sugar (ribose), three
phosphate groups
Has two high energy bonds, relatively unstable phosphoanhydride bonds. Unstable
because phosphate groups have negative charges associated with them. Negative
charges overlap one another, repel each other, making bonds relatively unstable
(equated with high energy). Release energy when broken.
ATP Hydrolysis
7.2 kcal of energy is released for each molecule of ATP hydrolyzed with water; this
energy can be used to drive endergonic reactions
ATP + H2O > ADP + Pi (delta g = -7.3 kcal/mol)
Coupling ATP hydrolysis with G6P synthesis. ATP hydrolysis that releases 7.3 kcal/mol
can be used to drive endergonic reactions or provide activation energy for exergonic
H2O + ATP > ADP + Pi (spontaneous, delta g = _7.3 kcal/mol)
Pi + Glucose > G6P + H2O (non-spontaneous, delta g = +3.3 kcal/mol)
ATP + Glucose > G6P + ADP (spontaneous, delta g = -4.0 kcal/mol)
ATP and Energy Coupling
Hydrolysis of ATP is an exergonic reaction that can be coupled to make otherwise
endergonic reactions proceed spontaneously. Coupling reactions require enzymes
The ATP Cycle
ATP is synthesized by using energy from photosynthesis or respiration. ATP is hydrolyzed
to release energy needed for cellular work.
o Photosynthesis and/or respiration provide the energy required to synthesis ATP
o Hydrolysis od ATP provides energy to drive endergonic reactions in the cell
Repeated ATP hydrolysis powers the changes in shape that allow DNA helicase to move.
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