Advanced Examination on Cell and Molecular Biology Comprehensive Test for Mastery of Molecular Mechanisms in Cells Section 1: Short Answer (15 marks) Answer all questions in brief. Describe the role of ribosomal RNA (rRNA) in protein synthesis. Answer:

Advanced Examination on Cell and Molecular Biology Comprehensive Test for Mastery of Molecular Mechanisms in Cells Section 1: Short Answer (15 marks) Answer all questions in brief. Describe the role of ribosomal RNA (rRNA) in protein synthesis. Answer: rRNA is a component of ribosomes, providing a structural and functional scaffold for protein synthesis. It helps align mRNA and tRNAs and catalyzes peptide bond formation. What is the function of telomerase in DNA replication? Answer: Telomerase extends the telomeres at the ends of chromosomes, preventing shortening during replication, which is crucial for maintaining genomic integrity. Explain the concept of the fluid mosaic model of the plasma membrane. Answer: The fluid mosaic model describes the plasma membrane as a fluid combination of lipids, proteins, and carbohydrates. Phospholipids form a bilayer that allows lateral movement, while proteins embedded in the membrane serve various functions such as signaling and transport. Section 2: Multiple Choice (20 marks) Choose the correct answer. Which phase of the cell cycle involves the replication of DNA? a) G0 Phase b) G1 Phase c) S Phase d) M Phase Answer: c) S Phase The enzyme responsible for catalyzing the removal of introns from mRNA precursors is: a) Helicase b) DNA polymerase c) Spliceosome d) RNA polymerase Answer: c) Spliceosome Which of the following is NOT a component of the cytoskeleton? a) Microtubules b) Actin filaments c) Intermediate filaments d) Chromatin Answer: d) Chromatin Section 3: True or False (10 marks) Indicate whether the following statements are true or false. The Golgi apparatus modifies proteins by glycosylation before they are sent to their final destination. Answer: True The citric acid cycle occurs in the cytoplasm. Answer: False (It occurs in the mitochondrial matrix.) Apoptosis is a form of programmed cell death, often termed "cell suicide." Answer: True Section 4: Essay (25 marks) Choose ONE of the following essay questions and write a detailed response. Discuss the process of DNA replication in eukaryotic cells, highlighting the roles of major enzymes involved. Answer: (Detailed answer describing initiation, elongation, and termination steps, with focus on helicase, DNA polymerase, primase, and ligase.) Explain the mechanisms of cell signaling via G-protein coupled receptors (GPCRs). Answer: (Detailed answer explaining the steps of GPCR activation, signal transduction, and the importance of secondary messengers like cAMP.)