Bioenergetics and Enzymes

What is the difference between energy transfer in the form of heat, and energy transfer in the form of work?

Energy transfer in the form of heat increases the random motion of particles such as molecules and atoms. Work, however, brings about any other kind of change, such as chemical work, transport work, and mechanical work.

Thermodynamically speaking, how can ATP hydrolysis drive reactions that would not otherwise happen?

ATP hydrolysis is an exergonic process. When it is coupled with an endergonic process, the combined G might be negative, and so the
combined reaction would be thermodynamically favourable. In many cases, the reaction coupling happens by means of the transfer of a phosphate group from ATP to a substrate molecule.

Why do enzymes have saturation kinetics?

A given quantity of enzyme will have a finite number of active sites, each taking a certain amount of time to process substrates. When the substrate concentration reaches a high enough value that a new substrate molecule diffuses to the active site the instant the products from the previous catalytic cycle are ejected, further increases in substrate concentration will have no effect on the rate of reaction.

Why does the rate of an enzyme-catalyzed reaction increase with increasing temperature up to the optimum temperature? Why does the rate of reaction fall when the optimum temperature is exceeded?

a) As the temperature rises, substrates diffuse into active sites more quickly, and the collisions of molecules are more violent; the activation energy is reached by a greater proportion of molecules at a given moment, so the reaction rate increases.
b) The enzyme denatures.

What are the enzymes that catalyze ATP hydrolysis?

ATPases