Description : Regulation of haem synthesis occurs by (A) Covalent modification (B) Repression - derepression (C) Induction (D) Allosteric regulation
Last Answer : Answer : B
Description : Enzyme inhibition caused by a substance resembling substrate molecule is (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) Allosteric inhibition
Last Answer : Answer : A
Description : Allosteric inhibition is also known as (A) Competitive inhibition (B) Non-competitive inhibition (C) Feedback inhibition (D) None of these
Last Answer : Answer : C
Description : The sulfa drugs work by _______ with PABA in making folic acid. a. Positive Feedback b. Negative Feedback c. Competitive Inhibition d. Allosteric Inhibition
Last Answer : c. Competitive Inhibition
Description : An enzyme of pyrimidine nucleotides biosynthesis regulated at the genetic level by apparently coordinate repression and derepression is (A) Carbamoyl phosphate synthetase (B) Dihydroorotate dehydrogenase (C) Thymidine kinase (D) Deoxycytidine kinase
Description : Which one of the following regulatory actions involves a reversible covalent modification of the enzyme? (A) Phosphorylation of ser-OH on the enzyme (B) Allosteric modulation (C) Competitive inhibition (D) Non-competitive inhibition
Description : Which of the following regulatory reactions involves a reversible covalent modification of an enzyme? (A) Phosphorylation of serine OH on the enzyme (B) Allosteric modulation (C) Competitive inhibition (D) Non-competitive inhibition
Description : An example of feedback inhibition is (A) Allosteric inhibition of hexokinase by glucose6-phosphate (B) Cyanide action on cytochrome (C) Sulpha drug on folic acid synthesizer bacteria (D) Reaction between succinic dehydrogenase and succinic acid
Description : The ability of CTP to bind to aspartate carbamoyltransferase and shut down the synthesis of more A- enzyme induction B- enzyme repression C- feedback inhibition of enzyme activity D- none of these
Last Answer : feedback inhibition of enzyme activity
Description : The inhibition of succinate dehydrogenase by malonate by (A) Competitive inhibition (B) Non-competitive inhibition (C) Uncompetitive inhibition (D) Feedback inhibition
Description : An example of enzyme inhibition: (A) Reversible inhibition (B) Irreversible inhibition (C) Allosteric inhibition (D) All of these ENZYMES 151
Last Answer : Answer : D
Description : Allosteric inhibition (A) Makes active site unifit for substrate (B) Controls excess formation and end product (C) Both (A) and (B) (D) None of these
Description : Difference between competitive and allosteric inhibition -Biology
Last Answer : answer:
Description : Glucose-6-phosphatase and PEP carboxy kinase are regulated by (A) Covalent modification (B) Allosteric regulation (C) Induction and repression (D) All of these
Description : Acetyl CoA carboxylase regulates fatty acid synthesis by which of the following mechanism? (A) Allosteric regulation (B) Covalent modification (C) Induction and repression (D) All of these
Description : Pyruvate carboxylase is regulated by (A) Induction (B) Repression (C) Allosteric regulation(D) All of these
Last Answer : D
Description : What is it called when an enzyme is blocked at its active site so the normal substrate can't bind? a. Competitive Inhibition b. Feedback Inhibition c. Noncompetitive Inhibition d. Pathway Modulation
Last Answer : a. Competitive Inhibition
Description : Which inactivates an enzyme by occupying its active site? (A) Competitive inhibitor (B) Allosteric inhibitor (C) Non-competitive inhibitor (D) All of these
Description : Feedback inhibition of enzyme action is affected by (A) Enzyme (B) Substrate (C) End products (D) None of these
Description : Which factor is responsible for inhibition of enzymatic process during feedback? (a) Substrate (b) Enzymes (c) End product (d) Temperature
Last Answer : (c) End product
Description : Give examples for allosteric inhibition.
Last Answer : ALA synthase, aspartyl trans-carbamoylase, HMG CoA reductase
Description : What are the salient features of allosteric inhibition?
Last Answer : (1) The inhibitor is not a substrate analogue. (2) It is partially reversible when excess substrate is added. (3) Km is usually increased. (4) Vmax is reduced. (5) Most allosteric enzymes possess quaternary structure. They are made up of subunits.
Description : What is allosteric inhibition?
Last Answer : Allosteric enzyme has one catalytic site where the substrate binds and another separate allosteric site where the modifier binds.
Description : In non competitive enzyme activity inhibition, inhibitor (A) Increases Km (B) Decreases Km (C) Does not effect Km (D) Increases Km
Description : In reversible non-competitive enzyme activity inhibition (A) Inhibitor bears structural resemblance to substrate (B) Inhibitor lowers the maximum velocity attainable with a given amount of enzyme (C) Km is increased (D) Km is decreased
Description : In reversible non-competitive enzyme activity inhibition (A) Vmax is increased (B) Km is increased (C) Km is decreased (D) Concentration of active enzyme is reduced
Description : A sigmoidal plot of substrate concentration ([S]) verses reaction velocity (V) may indicate (A) Michaelis-Menten kinetics (B) Co-operative binding (C) Competitive inhibition (D) Non-competitive inhibition
Description : Give examples of non-competitive inhibition.
Last Answer : Di-isopropyl fluoro phosphate inhibits trypsin, fluoride inhibits and enolase.
Description : What are the salient features of non-competitive inhibition?
Last Answer : Non-competitive inhibitor has no structural similarity with the substrate. 2. It is generally not reversible 3. Km is not changed. 4. Vmax is reduced.
Description : A substance unrelated to substrate but capable of reversibly changing activity of enzyme by binding to a site other than active site is called (a) Competitive inhibitor (b) Non-competitive inhibitor (c) Catalytic inhibitor (d) Allosteric modulator/inhibitor
Last Answer : Ans. ((d))
Description : Negative regulation of protein synthesis is accomplished by A- allosteric inhibition B- the binding of RNA polymerase to the promoter C- the binding of a repressor to the DNA D- the binding of a repressor to the RNA polymerase
Last Answer : the binding of a repressor to the DNA
Description : The organophosphates produce irreversible inhibition of cholinesterase because: A. They bind to an allosteric site of the enzyme resulting in unfavourable conformation of esteratic site to bind ... degradation of enzyme molecules D. They are neither metabolized nor excreted from the body
Last Answer : B. Regeneration time of the phosphorylated enzyme is longer than the turnover time of the enzyme molecules
Description : In the pathway of de novo synthesis of purine nucleotides, all the following are allosteric enzymes except (A) PRPP glutamyl amido transferase (B) Adenylosuccinate synthetase (C) IMP dehydrogenase (D) Adenylosuccinase
Description : Allosteric enzymes contain (A) Multiple subunits (B) Single chain (C) Two chains (D) Three chains
Description : Which one of the following statements is not characteristic of allosteric enzymes? (A) They frequently catalyze a committed step early in a metabolic pathway (B) They are often composed of subunits (C) They follow Michaelis-Menten kinetics (D) They frequently show cooperativity for substrate binding
Description : In which of the following types of enzymes an inducer is not required? (A) Inhibited enzyme (B) Cooperative enzyme (C) Allosteric enzyme (D) Constitutive enzyme
Description : All of the following are allosteric enzymes except (A) Citrate synthetase (B) a-Ketoglutarate dehdrogenase (C) Succinate thiokinase (D) Succinate dehydrogenase
Description : A demonstrable inducer is absent in (A) Allosteric enzyme (B) Constitutive enzyme (C) Inhibited enzyme (D) Co-operative enzyme ENZYMES 141
Description : Cytosolic and mitochondrial carbamoyl phosphate synthetase have the following similarity: (A) Both use ammonia as a substance (B) Both provide carbamoyl phosphate for urea synthesis (C) Both require N-acetylglutamate as an activator (D) Both are allosteric enzymes
Description : Regulation of ACTH secretion occurs through (A) Corticotropin releasing hormone (CRH) and corticotropin release inhibiting hormone (CRIH) of hypothalamus (B) Feedback inhibition by cortisol (C) CRH and feedback inhibition by cortisol (D) CRIH and feedback inhibition by cortisol
Description : Secretion of prolactin is regulated by (A) Feedback inhibition (B) Prolactin releasing hormone (C) Prolactin release inhibiting hormone (D) All of these
Description : Secretion of growth hormone is inhibited by (A) Somatomedin C (B) Somatostatin (C) Feedback inhibition(D) All of these
Description : Feedback inhibition of enzyme is influenced by (A) Enzyme (B) External factors (C) End product (D) Substrate
Description : In competitive inhibition which of the following kinetic effect is true ? (A) Decreases both Km and Vmax (B) Increases both Km and Vmax (C) Decreases Km without affecting Vmax (D) Increases Km without affecting Vmax
Description : In competitive inhibition of enzyme action (A) The apparent Km is decreased (B) The apparent Km is increased (C) Vmax is decreased (D) Apparent concentration of enzyme molecules decreased
Description : Competitive inhibition can be relieved by raising the (A) Enzyme concentration (B) Substrate concentration (C) Inhibitor concentration (D) None of these
Description : In competitive inhibition, the inhibitor (A) Competes with the enzyme (B) Irreversibly binds with the enzyme (C) Binds with the substrate (D) Competes with the substrate
Description : In competitive enzyme activity inhibition (A) Apparent Km is decreased (B) Apparent Km is increased (C) Vmax is increased (D) Vmax is decreased
Description : In competitive enzyme activity inhibition (A) The structure of inhibitor generally resembles that of the substrate (B) Inhibitor decreases apparent Km (C) Km remains unaffective (E) Inhibitor decreases Vmax without affecting Km