biochem chapter12

uncompetitive

...inhibition, the inhibitor binds only to the enzyme-substrate complex, not to the free enzyme.

Which of the following groups of isotopes includes only radioactive isotopes that are commonly used in biochemical experiments?

3H, 14C, 32P, 35S

E. coli aspartate transcarbamoylase has 6 catalytic subunits and

6 regulatory subunits.

If ATP is a substrate for an enzyme, and ADP was found to be a more potent competitive inhibitor than adenosine for the reaction, which of the following would be a plausible explanation?

The phosphate groups of ADP must be important for binding.

The catalytic activity of an enzyme can be regulated by controlling the amount of the enzyme available and by structural alterations of the enzyme that influence substrate binding.

True

The effects of uncompetitive inhibition on Vmax are not reversed by increasing substrate concentration

True

The vo versus [S] plot for ATCase is sigmoidal, rather than hyperbolic as it is in enzymes that follow the Michaelis-Menten model.

True

A Lineweaver-Burk plot is also referred to as

a linear plot. a double reciprocal plot.

An enzyme's substrate-binding affinity may vary with the binding of small molecules called

allosteric effectors.

Parallel lines on a Lineweaver-Burk plot indicate

decrease in KM. decrease in Vmax. uncompetitive inhibition

rate equation

describes the progress of a reaction as a function of time.

All inhibitors must resemble the substrate in some way.

false

Noncovalent modifications of an enzyme cannot significantly influence its activity.

false

Steady state kinetic analysis is commonly used to establish reaction mechanisms.

false

Structural differences between the T-state and the R-state of ATCase are hard to discern.

false

The double-reciprocal plots for irreversible inhibition resemble those for competitive inhibition.

false

The reaction order of an elementary reaction corresponds to the number of different types of molecules that must simultaneously collide to generate a product.

false

Pyrimidine synthesis is regulated by feedback ... of aspartate transcarbamoylase.

inhibition

competitive

inhibitor binds only to the free enzyme, not to the enzyme-substrate complex.

Substances that reduce an enzyme's activity by reversibly combining with the enzyme are called

inhibitors

The study of enzymatic reaction rates is called enzyme

kinetics

bisubstrate

reactions are enzyme reactions with two substrates.

The Lineweaver-Burk plot is also known as the double-

reciprocal plot

A large part of the modern pharmaceutical arsenal consists of enzyme inhibitors.

true

All enzymes can be analyzed such that their reaction rates and their overall efficiencies can be quantitated.

true

Mixed inhibition is characterized by two dissociation constants for inhibitor binding.

true

The Michaelis-Menten equation describes a rectangular hyperbola.

true

The rate of an elementary reaction is proportional to the frequency with which the reacting molecules come together.

true