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• Représentez une bulle de réplication et positionnez les acteurs moléculaires (y compris la pol I)

For efficient nucleophilic catalysis, a group such as the sulfhydryl on a cysteine residue must be able to form a good ______, in addition to being a good nucleophile.

_______ is a serine protease that has a specificity pocket that binds small hydrophobic side chains. A) chymotrypsin B) trypsinC) lysozyme D) trypsinogen E) elastase

Serine proteases use _________ to catalyze the cleavage of a peptide bond. A) covalent catalysis B) proximity and orientation catalysis C) general base catalysis D) electrostatic catalysis E) all of the above

Which of the following considerations in the rate of a given reaction can be optimized by enzymatic catalysis: A) the proximity of the reacting groups B) the rotational motions of the substrates and catalytic groups C) the orientations of the substrates and catalytic groups D) all of the above E) none of the above

• Si une fourche de réplication se déplace à une vitesse de 100 paires de bases par seconde, quelle est la quantité d'ADN synthétisée en une minute (faites un schéma et exprimez cette quantité en nucléotides) ?

What type of chemical species can participate in catalysis by binding substrates to orient them properly, by undergoing reversible changes in oxidation state, and by stabilizing negative charges: A) nucleophilic amino acids B) protons C) phosphate salts D) transition metal anions E) transition metal cations

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Lysozyme catalyzes the hydrolysis of: A) a(1-4) glycosidic linkages. B) b(1-4) glycosidic linkages. C) peptide bonds. D) bacterial cell wall proteoglycans E) all of the above

Clustering several amino acid residues with favorable pK values at an active site can promote a(n) _________ catalytic mechanism.

The covalent bonds connecting monomer units in sugars can be formed by the removal of a water molecule. This reaction is referred to as:

Metal ion cofactors with more than one oxidation state may assist in catalysis by the ______ class of enzymes.

In affinity labeling, a technique used to study enzyme mechanisms, A) a compound designed to bind at the active site reacts with and therefore permits the identification of a nearby group. B) a fluorescent group is attached to the substrate to identify the position of the active site. C) highly purified enzyme is obtained by affinity chromatography for mechanistic studies. D) a radioactive isotope is incorporated into the substrate to identify the position of the active site. E) genetic modification of amino acid residues is used to study the binding properties of the active site

When atoms gain or lose electrons, they become negatively or positively charged. These negatively or positively charged atoms are known as

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Which one of the following is correct? A) All enzymes are highly specific for the reactions they catalyze. B) Prosthetic groups are loosely associated with the polypeptide chain of an enzyme. C) Activation of zymogens, such as proelastase, requires an oxidation-reduction reaction at a particular amino acid side chain. D) If an enzyme-catalyzed reaction requires a group with a low pK to be deprotonated and a group with a higher pK to be protonated, the pH vs. velocity curve will have a peak in the middle. E) The proximity effect, a result of bringing substrates close to their catalytic groups in the active site, can result in a rate enhancement on the order of 10^6 .

Metal ion cofactors can ______ the substrate at the active site, providing catalytic enhancement.

If an enzyme-catalyzed reaction has a low rate at low pH and high rate at higher pH, this implies that a group on either the enzyme or the substrate must be ______ for an efficient reaction.