An effect that appears to be a major factor in the stability of the photosynthetic apparatus is photoinhibition, which occurs when excess excitation arriving at the PSII reaction center leads to its inactivation and damage due to

#Question id: 559

#Unit 1. Molecules and their Interaction Relevant to Biology

In competitive inhibition, an inhibitor:

#Question id: 560

#Unit 1. Molecules and their Interaction Relevant to Biology

Vmax for an enzyme-catalyzed reaction:

#Question id: 561

#Unit 1. Molecules and their Interaction Relevant to Biology

Enzyme X exhibits maximum activity at pH = 6.9.  X shows a fairly sharp decrease in its activity when the pH goes much lower than 6.4.  One likely interpretation of this pH activity is that:

#Question id: 562

#Unit 1. Molecules and their Interaction Relevant to Biology

Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site; this enzyme-inhibitor bond is not cleaved by the enzyme.  This is an example of what kind of inhibition?

#Question id: 563

#Unit 1. Molecules and their Interaction Relevant to Biology

Both water and glucose share an —OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase.  Glucose, however, is about a million times more reactive as a substrate than water.  The best explanation is that:

#Question id: 564

#Unit 1. Molecules and their Interaction Relevant to Biology

A good transition-state analog: