Discussion 5 Flashcards
Which of the following statements about phosphorylation of enzymes is FALSE?
The phosphorylation of an enzyme results in a change in its conformation, thereby increasing its activity.
Phosphorylation is a reversible covalent modification.
The phosphorylation of enzymes is catalyzed by other enzymes called kinases.
The phosphorylation of enzymes is one mechanism via which hormones elicit an intracellular response.
The phosphorylation of an enzyme results in a change in its conformation, thereby increasing its activity.
Zymogens are not enzymatically active because _____.
they do not contain the cofactors required for catalysis
they are the product of mutated genes
their active sites are distorted and incapable of enzymatic activity
the pH of their environment is not optimal for activity
none of the above
their active sites are distorted and incapable of enzymatic activity
Protein kinases are involved in _____.
the digestion of drugs to potentially toxic by-products
the degradation of enzymes to the component amino acids
the phosphorylation of a wide variety of proteins
the metabolism of drugs to water soluble, excretable compounds
all of the above
the phosphorylation of a wide variety of proteins
This chapter discusses the regulation of proteins by allostery, phosphorylation, or proteolytic cleavage. Of these,
- which is irreversible?
- Which type of regulation occurs most quickly?
- Which type of regulation is the most specific?
- Which type of regulation has broad specificity and is reversible?
- Proteolytic cleavage
- Allostery
- Allostery
- Phosphorylation.
What is the difference between allosteric and orthosteric regulation?
All enzymes are regulated orthosterically only.
All enzymes are regulated allosterically only.
Only in allosteric regulation of an enzyme does the substrate bind to the active site
In allosteric regulation of an enzyme, the substrate binds to the allosteric site
In allosteric regulation of an enzyme, a molecule other than the substrate binds a site other than the active site
In allosteric regulation of an enzyme, a molecule other than the substrate binds a site other than the active site
In the sequential model of allosterism, as regulatory molecules bind to allosteric sites,
A) the active site-containing subunit shifts from T to R state
B) the active site-containing subunit is activated
C) the entire complex exists in the T or R state
D) subunits in the T state have high affinity
E) Both A and B
E) Both A and B
Heterotropic regulation
I. occurs with a molecule other than the protein’s substrate
II. occurs with regulator binding at a site other than the active site
III. influences substrate binding
IV. is a type of competitive inhibition
I and II
II and III
II, III and IV
I, III and IV
I, II and III
I, II and III
As associated with hemoglobin, heme is considered a _____.
catalyst
subunit
coenzyme
cofactor
none of the above
cofactor
In its reduced form, the central ion of the heme group of hemoglobin is _____.
Cu+
Cu2+
Fe2+
Fe3+
none of the above
Fe2+
Myoglobin is _____; hemoglobin is _____.
monomeric; dimeric
monomeric; trimeric
monomeric; tetrameric
dimeric; trimeric
dimeric; tetrameric
monomeric; tetrameric
The individual hemoglobin subunits and myoglobin share similar _____ structure but have rather different _____ structure.
primary; secondary
secondary; tertiary
primary; tertiary
secondary and tertiary; primary
primary and secondary; tertiary
secondary and tertiary; primary
A plot of the binding of oxygen to myoglobin as a function of pO2 gives a _____ shape; a similar plot for hemoglobin gives a _____ shape.
sigmoidal; sigmoidal
sigmoidal; hyperbolic
hyperbolic; sigmoidal
hyperbolic; hyperbolic
hyperbolic; exponential
hyperbolic; sigmoidal
The idea that binding of one molecule of oxygen to hemoglobin enhances further binding of oxygen to hemoglobin is called _____.
homologous binding
cooperativity
fractional saturation
allosterism
none of the above
cooperativity
With respect to oxygen saturation, hemoglobin is _____ saturated at the pO2 of the lungs and _____ saturated at the pO2 of the tissue
20%; 20%
25%; 20%
50%; 20%
50%; between 30 and 70%
> 90%; 10-30%
> 90%; 10-30%
The Bohr effect refers to
the decrease in affinity of Hb (hemoglobin) for O2 when the pH goes down
the decrease in affinity of Hb for O2 when the pH goes up
the increase in the affinity of Hb for O2 when the O2 concentration goes up
the decrease in affinity of Hb for O2 when the BPG concentration goes up
the decrease in affinity of Hb for O2 when the BPG concentration goes down
the decrease in affinity of Hb (hemoglobin) for O2 when the pH goes down
