1. What are ribozymes?
A. Protein-based enzymes
B. RNA molecules with catalytic activity
C. DNA molecules with enzymatic activity
D. Lipid molecules with signaling roles
Answer: B. RNA molecules with catalytic activity
Explanation: Ribozymes are RNA molecules capable of catalyzing specific biochemical reactions, similar to protein enzymes.
2. Which of the following is an example of a ribozyme?
A. DNA polymerase
B. Telomerase RNA
C. Hammerhead RNA
D. tRNA synthetase
Answer: C. Hammerhead RNA
Explanation: Hammerhead RNA is a well-known ribozyme that cleaves itself in the presence of magnesium ions.
3. What is the primary role of ribozymes in cells?
A. Structural support
B. Catalysis of RNA splicing or cleavage
C. DNA replication
D. Lipid synthesis
Answer: B. Catalysis of RNA splicing or cleavage
Explanation: Ribozymes are mainly involved in catalyzing RNA processing events, such as splicing and cleavage.
4. Which ion is crucial for ribozyme activity?
A. Sodium (Na+^+)
B. Potassium (K+^+)
C. Magnesium (Mg2+^2+)
D. Calcium (Ca2+^2+)
Answer: C. Magnesium (Mg2+^2+)
Explanation: Magnesium ions stabilize the negative charge of RNA and play a critical role in ribozyme catalysis.
5. The catalytic activity of ribozymes was first discovered in which organism?
A. Bacteria
B. Viruses
C. Tetrahymena thermophila
D. Drosophila melanogaster
Answer: C. Tetrahymena thermophila
Explanation: The self-splicing activity of introns in Tetrahymena thermophila was the first evidence of ribozyme function.
6. What type of bond cleavage is catalyzed by the hammerhead ribozyme?
A. Phosphodiester bond
B. Hydrogen bond
C. Glycosidic bond
D. Disulfide bond
Answer: A. Phosphodiester bond
Explanation: Hammerhead ribozymes catalyze the cleavage of phosphodiester bonds in RNA molecules.
7. Which ribozyme is associated with peptide bond formation?
A. Spliceosome
B. Ribosomal RNA (rRNA)
C. Hammerhead ribozyme
D. Hairpin ribozyme
Answer: B. Ribosomal RNA (rRNA)
Explanation: The ribosome, composed of rRNA, acts as a ribozyme to catalyze peptide bond formation during translation.
8. What distinguishes ribozymes from other RNA molecules?
A. Length of the molecule
B. Secondary structure formation
C. Catalytic activity
D. Sequence complexity
Answer: C. Catalytic activity
Explanation: Ribozymes are unique among RNA molecules due to their ability to catalyze biochemical reactions.
9. Which structural feature is critical for ribozyme function?
A. Primary sequence
B. 3D folding of RNA
C. Circular structure
D. Covalent modifications
Answer: B. 3D folding of RNA
Explanation: The three-dimensional folding of ribozymes is essential for their catalytic activity and specificity.
10. What is the significance of self-splicing introns?
A. They replicate DNA
B. They catalyze their removal from RNA
C. They transport molecules across membranes
D. They bind to proteins for translation
Answer: B. They catalyze their removal from RNA
Explanation: Self-splicing introns are ribozymes that remove themselves from precursor RNA molecules.
11. Ribozymes are primarily composed of:
A. RNA and proteins
B. Only RNA
C. DNA and RNA
D. RNA and lipids
Answer: B. Only RNA
Explanation: Ribozymes are purely RNA molecules with intrinsic catalytic properties.
12. Which Nobel Prize-winning discovery involved ribozymes?
A. Discovery of the double helix
B. Discovery of catalytic RNA
C. Discovery of CRISPR-Cas9
D. Discovery of DNA sequencing
Answer: B. Discovery of catalytic RNA
Explanation: Sidney Altman and Thomas Cech won the Nobel Prize for discovering the catalytic activity of RNA.
13. What does the term “ribozyme” stand for?
A. Ribosomal enzyme
B. RNA enzyme
C. Ribose enzyme
D. Ribosomal zymogen
Answer: B. RNA enzyme
Explanation: The term “ribozyme” is a combination of “RNA” and “enzyme,” signifying RNA’s enzymatic role.
14. Which ribozyme is involved in viral replication?
A. Hammerhead ribozyme
B. Group II intron
C. RNase P
D. Hepatitis delta virus (HDV) ribozyme
Answer: D. Hepatitis delta virus (HDV) ribozyme
Explanation: The HDV ribozyme facilitates cleavage and ligation of RNA during viral replication.
15. RNase P is a ribozyme that processes:
A. tRNA precursors
B. mRNA splicing
C. rRNA synthesis
D. Viral RNA cleavage
Answer: A. tRNA precursors
Explanation: RNase P cleaves the 5′ leader sequence from precursor tRNA molecules, making them functional.
16. The hammerhead ribozyme was originally found in:
A. Mammalian cells
B. Viral genomes
C. Viroids
D. Fungi
Answer: C. Viroids
Explanation: Hammerhead ribozymes were discovered in plant viroids, where they cleave RNA during replication.
17. Group I introns are primarily found in:
A. Bacteria
B. Eukaryotic mitochondria and chloroplasts
C. Viral genomes
D. Mammalian cells
Answer: B. Eukaryotic mitochondria and chloroplasts
Explanation: Group I introns are self-splicing introns commonly found in organellar genomes.
18. The ribosome catalyzes peptide bond formation using which mechanism?
A. Protein-based enzymatic activity
B. RNA-based catalytic activity
C. DNA-based replication
D. Lipid-based signaling
Answer: B. RNA-based catalytic activity
Explanation: The ribosome\u2019s peptidyl transferase center, composed of rRNA, catalyzes peptide bond formation.
19. Which type of reaction is typically catalyzed by ribozymes?
A. Oxidation-reduction reactions
B. RNA cleavage or splicing reactions
C. Lipid hydrolysis reactions
D. Protein folding reactions
Answer: B. RNA cleavage or splicing reactions
Explanation: Ribozymes primarily catalyze reactions involving RNA cleavage, splicing, or ligation.
20. Ribozymes play a crucial role in the RNA world hypothesis because:
A. They store genetic information
B. They catalyze reactions without proteins
C. They replicate DNA
D. They synthesize lipids
Answer: B. They catalyze reactions without proteins
Explanation: Ribozymes demonstrate that RNA could act as both genetic material and catalyst, supporting the RNA world hypothesis.
