Chapter 4: ATP and ADP Cycle Flashcards
Define energy
capacity to cause change
What is phosphorylation?
the transfer of phosphate group from one molecule to another
What is Adenosine triphosphate?
an organic compound that temporarily stores and provides energy to drive many processes in living cells
What are coupled reactions?
simultaneous reactions in which one provides the energy that drives the other
Why is ATP hydrolysis considered an exergonic reaction?
The hydrolysis of one ATP molecule releases 7.3 kcal/mol of energy (∆G = −7.3 kcal/mol of energy).
What is Kinetic energy?
energy associated with relative motion of objects
What is Potential Energy?
energy possessed by a matter at rest
What are the two most important energy transformations?
The most important energy transformations are photosynthesis and cellular respiration.
What is metabolism on a cellular level?
The word metabolism encompasses all of the chemical reactions in cells, including those that build new molecules and those that break down existing ones. Each reaction rearranges atoms into new compounds, and each reaction either absorbs or releases energy.
Distinguish between endergonic and exergonic reactions.
An endergonic reaction requires an input of energy to proceed. Typically, endergonic reactions build complex molecules from simpler components.
In contrast, an exergonic reaction releases energy. Such reactions break large, complex molecules into their smaller, simpler components.
List and explain the three conditions that influence enzyme activity.
hydrogen ion concentration (pH)
Each enzyme has a pH value that it works at with maximum efficiency called the optimal pH. If the pH is lower or higher than the optimal pH, the enzyme activity decreases until it stops working
- Temperature
Each enzyme has a certain temperature at which it is more active.The enzyme activity gradually lowers as the temperature rises more than the optimal temperature until it reaches a certain temperature at which the enzyme activity stops completely due to the change of its natural composition. If it gets too hot, however, the enzyme rapidly denatures and can no longer function.
- Substrate concentration
Increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bound, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate.
How does an enzyme lower a reaction’s activation energy?
Enzymes speed reactions by lowering the activation energy, the amount of energy required to start a reaction (refer to the figure below). The enzyme brings reactants (also called substrates) into contact with one another, so that less energy is required for the reaction to proceed.
