Review questions for Enzymes 3 Flashcards
It is the ability to maintain a constant intracellular environment
despite changes in their external environment.
a. Dynamic steady state
b. Repression
c. Homeostasis
d. Physical compartmentation
c. Homeostasis
Segregation of certain metabolic pathways within specialized cell
types provides further means for:
a. Dynamic steady state
b. Repression
c. Homeostasis
d. Physical compartmentation
d. Physical compartmentation
Mean concentrations of metabolic intermediates remain relatively
constant overtime.
a. Dynamic steady state
b. Repression
c. Homeostasis
d. Physical compartmentation
a. Dynamic steady state
An excess of metabolite may curtain synthesis of its cognate
enzyme via:
a. Dynamic steady state
b. Repression
c. Homeostasis
d. Physical compartmentation
b. Repression
It is a process by which the end product of a multistep biosynthetic pathway binds to and inhibits an enzyme catalyzing one of the early steps in that high concentrations of D inhibit the
conversion of A to B.
a. Feedback inhibitors
b. Feedback regulation
c. Silence gene expression
d. Protein turn-over
a. Feedback inhibitors
Rationale: Feedback inhibitors regulate enzyme activity while feedback regulation devoid of mechanistic implications. Silence gene expression restricts the accessibility of genes to transcript factors. Protein turn-over is achieved from continuous synthesis and degradation ofprotein.
Changes in intrinsic catalytic efficiency affected by binding of
dissociable ligands that achieve regulation of enzymatic activity
within seconds.
a. Allosteric regulation
b. Covalent modification
c. Both A & B
d. None of the above
c. Both A & B
Both are considered as committed steps. Changes in protein level dominate long term adaptive requirements while changes in catalytic efficiency are best for rapid and transient alterations in
metabolic flux.
Catalysis at the active site may be modulated by the presence of
effectors at an allosteric site.
a. Zymogens
b. Allosteric enzymes
c. First messengers
d. Second messengers
b. Allosteric enzymes
Zymogens are proprotein forms of enzymes. Allosteric enzymes are those for which catalysis at the active site may be modulated by the presence of effectors at an allosteric site. First messenger is the hormone molecule or nerve impulse while the second messenger synthesize from ATP by enzyme adenylyl cyclase in response to hormones
It involve cis elements, specific DNA sequences located upstream of regulated genes, and trans-acting regulatory Proteins.
a. Induction
b. Repression
c. Ideal enzyme
d. A & B
e. B & C
d. A & B
The ff are characteristics of an ideal enzyme EXCEPT
a. It acts as a natural governor
b. It is responsible for the rate limiting reaction
c. Highly conserved among eukaryotes
d. Constitute efficient targets for regulatory intervention by drugs
c. Highly conserved among eukaryotes
Ubiquitin is a small 75 residue protein that is highly conserved among eukaryotes. The rest are characteristics on an ideal enzyme
It is responsible both for the regulated degradation of selected
cellular proteins and for the removal of defective or aberrant protein species.
a. Ubiquitin-proteasome pathway
b. Protein kinases
c. Protein phosphatases
d. Protein phosphorylation-dephosphorylation
a. Ubiquitin-proteasome pathway
Protein kinases phosphorylate proteins by catalyzing transfer of the terminal phosphoryl group of ATP to the hydroxyl groups. Protein phosphatases catalyze regenerated unmodified forms
of protein. Protein phosphorylation-dephosphorylation permits the
functional properties of the affected enzyme to be altered only for as long as it serves a specific need.
