35 clinical MCQs in Biochemistry. The following is an effect of administration of Allopurinol in humans. —. Kenya, Africa and global revision.
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Q1. The following is an effect of administration of Allopurinol in humans. ---
- Elevated blood uric acid level
- Elevated uric acid levels in urine
- Elevated blood hypoxanthine levels
- Elevated blood xanthine levels
- Lower blood uric acid levels
Answer: Elevated blood uric acid level
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Q2. The following are precursors for de novo purine nucleotide biosynthesis. ---
- Formate ($N^{10}$- formyl Tetrahydrofolate)
- Aspartate
- Glycine
- Glutamate
- Bicarbonate
Answer: Formate ($N^{10}$- formyl Tetrahydrofolate)
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Q3. Regulation of purine de novo biosynthesis involves ---
- 5-Phosphoribosyl-1-pyrophosphate (PRPP)
- Adenyl-succinate synthetase
- IMP dehydrogenase
- GMP synthetase
- All the above
Answer: 5-Phosphoribosyl-1-pyrophosphate (PRPP)
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Q4. A key difference between purine and pyrimidine nucleotide de novo biosynthesis is that ---
- Carbamoyl phosphate synthetase II is for pyrimidine biosynthesis
- Carbamoyl phosphate synthetase II is for purine biosynthesis
- All reactions in purines are cytosolic
- All reaction in pyrimidine are cytosolic
- Orotate dehydrogenase is a mitochondrial reaction in pyrimidines
Answer: Carbamoyl phosphate synthetase II is for pyrimidine biosynthesis
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Q5. In eurkaryotic mRNA synthesis, the following are considered as a posttranscriptional modification ---
- Polyadenylation of the 5' end of 1º transcript.
- Removal of exons and joining of introns
- Addition of 7-methylguanosine Cap' at 5' end
- Methylation of Uracil residues
- All the above
Answer: Polyadenylation of the 5' end of 1º transcript.
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Q6. The effect of α - amanitin on eukaryotic transcription is that it ---
- Completely inhibits RNA polymerase I
- Completely inhibits RNA polymerase II
- Partially inhibits RNA polymerase I
- Partially inhibits RNA polymerase II
- Partially inhibits RNA polymerase III
Answer: Completely inhibits RNA polymerase I
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Q7. In E.coli , DNA polymerase I ---
- has 5 ' $\rightarrow$ 3 'exonuclease activity
- is responsible for hydrolysing RNA primers
- has 3 '$\rightarrow$ 5 'exonuclease activity
- has 5 ' $\rightarrow$ 3 'polymerase activity
- has 3 '$\rightarrow$ 5 'polymerase activity
Answer: has 5 ' $\rightarrow$ 3 'exonuclease activity
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Q8. In a RNA-DNA hybrid duplex ---
- U of RNA base pairs with T of DNA
- U of RNA base pairs with A of DNA
- T of RNA base pairs with A of DNA
- G of RNA base pairs with C of DNA
- C of RNA base pairs with A of DNA
Answer: U of RNA base pairs with T of DNA
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Q9. Several types of ribonucleic acids (RNA) can be found in cells. Of these ---
- ribosomal RNA (rRNA) is synthesized in the nucleolus.
- messenger RNA (mRNA) is synthesized in the nucleolus and carries the genetic information to the cytoplasm.
- messenger RNA (mRNA) is the major type of RNA found in the cell.
- transfer RNA (tRNA) acts as an "adaptor" between the amino acid and triplet code.
- transfer RNA(tRNA) exists as at least 20 different kinds
Answer: ribosomal RNA (rRNA) is synthesized in the nucleolus.
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Q10. Adenosine monophosphate (AMP) ---
- Is a nucleoside
- Can be cyclized in a reaction catalysed by adenylate cyclase to give cyclic 3',5' – AMP
- Is a component of both RNA and DNA
- Is an allosteric activator of phosphofructokinase
- Is formed, with ATP, from two molecules of ADP by the action of myokinase (adenylate kinase)
Answer: Is a nucleoside
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Q11. Lactose ---
- Is galactosyl-glucose
- Is a non-reducing sugar
- Is incapable of being digested by many human adults
- Shows mutarotation
- Cannot be digested by individuals with galactosaemia
Answer: Is galactosyl-glucose
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Q12. Glycogen ---
- Is a macromolecule with variable molecular weight
- Has a highly branched structure
- Is a reducing polysaccharide
- Is the major source of stored energy in the body
- Is deposited in excessively large amounts in the case of certain inherited metabolic disease
Answer: Is a macromolecule with variable molecular weight
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Q13. The common monosaccharides ---
- Contain asymmetric centres
- Are of two types, aldoses and ketoses
- Tend to exist as ring structures in solution
- Include glucose, galactose and raffinose
- Are all readily formed from glucose by living cells
Answer: Contain asymmetric centres
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Q14. Allosteric enzymes, which typically control the rate of throughput in a metabolic pathway ---
- Generally show a hyperbolic dependence of initial rate on substrate concentration
- Are always oligomeric
- Alter the equilibrium position of the reaction they catalyse
- Catalyze the final reaction in a metabolic pathway
- Are typified by aspartate transcabamylase (ATCase) from E. coli
Answer: Generally show a hyperbolic dependence of initial rate on substrate concentration
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Q15. The initial rate of an enzyme-catalysed reaction is ---
- Normally directly proportional to substrate concentration
- Normally directly proportional to enzyme concentration
- Always maximal at neutral pH
- Always maximal when the substrate concentration is equal to the Km (Michaelis constant)
- Independent of temperature
Answer: Normally directly proportional to substrate concentration
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Q16. The Michaelis-Menten model of enzyme action ---
- Assumes the formation of an enzyme-substrate complex
- Assumes the formation of a covalent intermediate between enzyme and substrate
- Explains the allosteric behaviour of certain regulatory enzymes
- Explains the stereospecificity of enzyme reactions
- Explains the maximum rate ($\text{V}_{\text{max}}$) attainable in enzyme-catalysed reactions
Answer: Assumes the formation of an enzyme-substrate complex
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Q17. The following are associated with the glyoxylate cycle ---
- Malate synthase
- Malate synthetase
- Isocitrate synthase
- Isocitrate lyase
- Succinate
Answer: Malate synthase
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Q18. The following enzymes(s) are not to be found in the TCA cycle ---
- Reversible
- Kinase(s)
- Hydrogenating
- Decarboxylating
- Phosphorylating
Answer: Reversible
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Q19. The sixth ($6^{\text{th}}$) step of glycolysis involves the participation of ---
- Phosphate
- NADH
- ADP
- A dehydrogenase
- A three (3) carbon molecule
Answer: Phosphate
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Q20. The carbon skeletons of the following amino acids enter the TCA cycle via succinylCoA in humans ---
- Threonine
- Isolenine
- Asparagine
- Valine
- Methionine
Answer: Threonine
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Q21. The degradation of the following amino acids are associated with methylmalonic acidemia ---
- Phenylalamine
- Aspartate
- Methionine
- Valine
- Leucine
Answer: Phenylalamine
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Q22. The biosynthesis of palmitic acid involves ---
- Transferases
- Reductases
- NADPH
- CoA-SH
- Sulfhydryl groups
Answer: Transferases
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Q23. With regards to the following ---
- Citric acid cycle intermediates are precursors of glucose.
- Alcohol consumption promotes gluconeogenesis
- Conversion of glucose 6-phosphate into free glucose is the first bypass reaction
- Conversion of phosphoenolpyruvate to pyruvate requires a bypass reaction.
- The pathway of gluconeogenesis shares seven steps with the pathway of glycolysis
Answer: Citric acid cycle intermediates are precursors of glucose.
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Q24. The following is correct about a mitochondrion ---
- The outer membrane is freely permeable to most small molecules and ions.
- The outer membrane contains some enzymes
- The inner membrane contains the electron transport chain and transport systems but lacks enzymes
- The matrix contains most of the TCA cycle enzymes.
- The ATP synthetase molecule is located on the inner side of the outer membrane
Answer: The outer membrane is freely permeable to most small molecules and ions.
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Q25. Buffer solutions ---
- Have relatively flat titration curves at the pH(s) where they buffer
- Are typically composed of a weak acid and its conjugate base
- Resist changes in pH when considerable acid or base is added.
- Buffers where the amount of conjugate base are nearly equivalent to the amounts of weak acid.
- For polyprotic acids, buffer best half-way between the two pKa values
Answer: Have relatively flat titration curves at the pH(s) where they buffer
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Q26. The following molecules are saturated aliphatics ---
- Propene
- Ethyne
- Benzene
- Butane
- Propanone
Answer: Propene
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Q27. Weak interactions in proteins include ---
- Hydrogen bonds
- Peptide bonds
- Van-der waals
- Phosphodiester bonds
- Hydrophobic bonds
Answer: Hydrogen bonds
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Q28. Lipids found in animal membranes include ---
- Cholesterol
- Waxes
- Triacylglycerols
- Phosphoglycerols
- Sphingolipids
Answer: Cholesterol
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Q29. All mammalian steroid hormones are formed from ---
- Purine
- Pyrimidine
- Cholesterol
- Pyrrole
- None of the above
Answer: Purine
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Q30. Which of the following statement about the biosynthesis of heme is false ---
- 85% of total heme synthesis occurs in red blood cells.
- Biosynthesis of heme Ceases when RBCs mature
- Synthesis is regulated at the level of the enzymes ferrochelatase
- Synthesis is regulated at the level of the enzymes porphobilinogen deaminase
- Limited amounts of heme are synthesized in the muscle for exclusive incorporation in myoglobin
Answer: 85% of total heme synthesis occurs in red blood cells.
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Q31. Secretion of insulin is stimulated by the following molecules EXCEPT ---
- Glucose
- Gastrointestinal hormones
- Amino acids
- Epinephrine
- Serotonin
Answer: Glucose
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Q32. The predominant glucocorticoid is ---
- Cortisol
- Aldosterone
- Dehydroephiandrosterone
- Androstenedione
- All of the above
Answer: Cortisol
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Q33. Which of the following statements is FALSE regarding acute intermittent porphyria ---
- Originates in the liver and is autosomal dominant
- Is caused by a deficiency in porphobilinogen deaminase, which is involved in the conversion of porphobilinogen (PBG) to uroporphyrinogen…
- Results in accumulation of PBG, uroprophryin, and 5-ALA in the plasma and the urine
- Patients have neuropsychiatric symptoms and abdominal pain (neurovisceral)
- Patients are photosensitive (cutaneous photosensitivity)
Answer: Originates in the liver and is autosomal dominant
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Q34. Bacterial cell wall peptidoglycan consists of ---
- A dissachariade of N-acetyl glucosamine and N-acetyl muramic acid
- A tetrapeptide of L-alanine, D-glutamine, L-lysine and D-alanine
- A pentaglycine bride
- A penta alanine bridge
- All of the above
Answer: A dissachariade of N-acetyl glucosamine and N-acetyl muramic acid
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Q35. Identify true and false statements
- Partly synthesized bacterial cell wall structure is transported out of the cell by a lipid carrier protein.
- Bacterial cell wall peptidoglycan is fully synthesized outside the cell
- Bacterial cell wall peptidoglycan is partly synthesized inside and partly outside the cell
- All energy for synthesis of bacterial peptidoglycan is supplied from outside the cell
- All of the above are true
Answer: Partly synthesized bacterial cell wall structure is transported out of the cell by a lipid carrier protein.