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BCH 361 EXAM 2 Study Questions with 100% Correct Verified Solutions| Latest Update
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BCH 361 EXAM 2 Study Questions with 100%Correct Verified Solutions| Latest Update
Enzymes are the ____ of biological systems - Answer catalysts
Catalysts are chemicals that - Answer enhance the rate of the reaction
without permanently being affected themselves
______________ whose active site can be modified by environmental signals - Answer
allosteric enzymes
Enzymes are characterized by their _____ and _______ and ________. - Answer
catalytic power; specificity to substrate; type of reaction
Enzymes are specific both in the _____ they catalyze and in their choices of _______ -
Answer reactions; substrate
Proteolytic enzymes catalyze the hydrolysis of _______. What is the reverse reaction? -
Answer hydrolysis of peptide bonds (aid in digestion and degradation of proteins).
-The reverse reaction is peptide bond formation, the forward reaction (hydrolysis)
is thermodynamically favored, but very slow without enzymes.
Enzymes speed up the rate of chemical reactions, but
Enzymes do not alter the - Answer free energy change ΔG of a reaction.
,Oxidoreductases - Answer These enzymes transfer electrons between molecules.
In other words, these enzymes catalyze oxidation-reduction reactions.
Transferases - Answer These enzymes transfer functional groups between molecules.
Aminotransferases are prominent in amino acid synthesis and degradation, where
they shuffle amine groups between donor and acceptor molecules.
Hydrolyases - Answer A hydrolyase cleaves molecules by the addition of water.
Trypsin, the proteolytic enzyme already discussed, is a hydrolyase.
Lyases - Answer A lyase adds atoms or functional groups to a double bond or
removes them to form double bonds.
Isomerases - Answer these enzymes move functional groups within a molecule
Ligases - Answer Ligases join two molecules at the expense of ATP hydrolysis. Ex:
DNA ligase
An enzyme without its cofactor is referred to as an - Answer apoenzyme the
complete, catalytically active enzyme is called a holoenzyme
Cofactors can be subdivided into two groups: - Answer (1) small organic molecules,
derived from vitamins, called coenzymes and (2) metals. Tightly bound coenzymes
are called prosthetic (helper) groups.
Co-substrate = loosely bound
Free energy (G) is a thermodynamic property that is a measure of useful energy, or
energy that is capable of doing work. To understand how enzymes operate, we need
to consider only two thermodynamic properties of the reaction: - Answer (1) the free-
,energy difference (ΔG) between the products and the reactants and (2) the free energy
required to initiate the conversion of reactants into products. The former determines
whether the reaction will take place spontaneously, whereas the latter determines the
rate of the reaction. Enzymes affect only the latter.
A reaction can take place spontaneously only if - Answer ΔG is negative.
"Spontaneously" in the context of thermodynamics means that the reaction will
take place without the input of energy and, in fact, the reaction releases energy.
Such reactions are said to be exergonic.
A reaction cannot take place spontaneously if ΔG is - Answer positive. An input of free
energy is required to drive such a reaction. These reactions are termed endergonic.
In a system at equilibrium, there is no net change in the concentrations of the
products and reactants, and ΔG is - Answer zero
Enzymes facilitate the formation of the transition state by decreasing - Answer
the activation energy
Enzymes decrease the activation energy but not the free energy change for the reaction.
Enzymes bring substrates together to form an ____________ on a particular region of
the enzyme called the _______. - Answer enzyme substrate complex; active site
The interaction of the enzyme and substrates at the active site promotes the
formation of - Answer the transition state
The active site of an enzyme.... - Answer is a series of amino acids that bind a substrate
, induced fit is when - Answer the enzyme changes its shape upon substrate binding.
It does not interact with their substrates like a lock and key
The active site of an enzyme: - Answer is a series of amino acids which bind
the substrate
An enzyme will specifically bind its substrate because of what type of interactions?
- Answer a large number of weak interactions at the active site.
The binding energy is greatest when - Answer the enzyme interacts with the transition
state, thus lower the free energy of the transition state.
Only the ______ can participate in all the interactions with the enzyme thus _________.
The full complement of such interactions is formed only when the substrate is in the
______ not at the _______ (induced fit model). - Answer correct substrate
maximize binding energy
transition state
initial state
The enzyme binds the transition state the strongest, which actually destabilizes the -
Answer substrate making the reaction easier
Pyrrole 2-carboxylic acid has trigonal geometry, thus - Answer it is a transition-state
analog and a potent inhibitor of proline racemase
essence of a catalyst: - Answer selective binding of the transition state!
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