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CMB521S - CELL AND MOLECULAR BIOLOGY - 1ST OPP - NOV 2025 |
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CMBS21S • 1st OPPORTUNITY EXAMINATION PAPER
27 OCTOBER 2025
n Am I BI A u n IVER s ITY
OF SCI En CE Ano TECH n OLOGY
FACULTY OF HEALTH, NATURAL RESOURCES AND APPLIED SCIENCES
DEPARTMENT CLINICAL OF HEALTH SCIENCES
QUALIFICATION : BACHELOR OF MEDICAL LABORATORY SCIENCES
QUALIFICATION CODE: 08BMLS
LEVEL: 5
COURSE CODE: CMBS21S
SESSION: 27 OCTOBER 2025
COURSE NAME: CELL AND MOLECULAR BIOLOGY
PAPER: FIRST OPPORTUNITY EXAMINATION
QUESTION PAPER
DURATION: 3 HOURS
MARKS: 122
EXAMINER(S)
FIRST OPPORTUNITY EXAMINATION PAPER
MR. HUBERT SHITALENI
MODERATOR: MS. VANESSA TJIJENDA
INSTRUCTIONS
ANSWER ALL THE QUESTIONS.
PERMISSIBLE MATERIALS
CALCULATOR
THIS QUESTION PAPER CONSISTS OF 7 PAGES (INCLUDING THIS FRONT PAGE)
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CMB521S • 1st OPPORTUNITY EXAMINATION PAPER
SECTION A
QUESTION 1
OCTOBER 2025
(30)
(20]
Assess the following statements and decide which answer is correct. Write only the
number of the question and the correct letter next to it.
1.1. According to the cell theory:
(1)
A. All cells have a nucleus.
B. All cells are derived from the division of preexisting cells.
C. Viruses are considered the simplest form of life.
D. All cells are motile.
1.2. Which of the following organelles is not part of the endomembrane system? (1)
A. Endoplasmic reticulum
B. Golgi apparatus
C. Mitochondrion
D. Lysosome
1.3. The primary function of the mitochondrion is:
(1)
A. Photosynthesis
B. Protein synthesis
C. Cellular respiration and ATP production
D. Storage of genetic information
1.4. Vesicular transport involves the movement of materials in:
(1)
A. Cytoskeletal filaments
B. Membrane-enclosed transport vesicles
C. Aqueous pores in the membrane
D. The cytosol as soluble proteins
1.5. The process by which a cell engulfs a large particle, such as a bacterium, is (1)
called:
A. Pinocytosis
B. Exocytosis
C. Phagocytosis
D. Receptor-mediated endocytosis
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CMBS215 - 1st OPPORTUNITY EXAMINATION PAPER
27 OCTOBER 2025
1.6. A protein destined for the lumen of the endoplasmic reticulum (ER) typically (1)
has:
A. A nuclear localisation signal
B. An ER signal sequence at its N-terminus
C. A mannose-6-phosphate tag
D. A KDEL sequence
1.7. The addition of oligosaccharide chains to proteins occurs primarily in the:
(1)
A. Cytosol and Nucleus
B. Mitochondria and Chloroplasts
C. Endoplasmic reticulum and Golgi apparatus
D. Lysosomes and Peroxisomes
1.8. The lipid bilayer is primarily held together by:
(1)
A. Covalent bonds between lipid tails
B. Hydrophobic interactions
C. Ionic bonds with water
D. Hydrogen bonds between phospholipid heads
1.9. Which type of membrane protein is embedded within the lipid bilayer?
(1)
A. Peripheral membrane protein
B. Lipid-anchored protein
C. Integral membrane protein
D. Extracellular matrix protein
1.10. Passive transport across a membrane:
(1)
A. Requires energy from ATP hydrolysis.
B. Moves solutes against their electrochemical gradient.
C. Includes simple diffusion and facilitates diffusion.
D. Is carried out only by channel proteins.
1.11. The Na+/K+ pump is an example of:
(1)
A. Passive transport
B. Active transport
C. Ligand-gated channel activity
D. Osmosis
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CMB521S- lst OPPORTUNITY EXAMINATION PAPER
OCTOBER 2025
1.12. Nuclear pore complexes allow for the transport of molecules between the {1)
:ytoplasm and nucleus. This transport is unique because:
A. It requires the protein to be completely unfolded.
B. It can actively transport large, fully assembled proteins.
C. It occurs through simple diffusion for all molecules.
D. It is mediated by vesicles budding from the nuclear envelope.
1.13. The first step in a signal transduction pathway is t ypically:
(1)
A. The hydrolysis of ATP.
B. The binding of a ligand to its receptor.
C. The activation of a transcription factor.
D. The phosphorylation of a target protein.
1.14. G-protein-coupled receptors (GPCRS) function by:
(1)
A. Directly phosphorylating intracellular proteins.
B. Forming a pore for ions to pass through upon ligand binding.
C. Activating an associated g-protein subunit upon ligand binding.
D. Directly entering the nucleus to regulate gene expression.
1.15. Cadherins are a class of cell adhesion molecules that mediate:
(1)
A. Cell-to-matrix adhesion in a calcium-independent manner.
B. Tight junctions that seal the space between cells.
C. Calcium-dependent adhesion between cells of the same type.
D. Tran sient adhesion of white blood cells to blood vessel walls.
1.16. The phase of the cell cycle where DNA replication occurs is:
(1)
A. Gl phase
B. S phase
C. G2 phase
D. M phase
1.17. The key regulators of the cell cycle that must be complexed with cyclins to {1)
become active are:
A. Proteases
B. Cyclin-dependent kinases (CDKS)
C. Phosphatases
D. Transcription factors
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CMBS21S - 1st OPPORTUNITY EXAMINATION PAPER
OCTOBER 2025
1.18. In the Watson and Crick model of DNA, the two polynucleotide chains are: (1)
A. Parallel and identical in sequence.
B. Antiparallel and complementary in sequence.
C. Held together by covalent bonds between bases.
D. Composed of a sugar-phosphate backbone on the inside.
1.19. The enzyme that synthesises the RNA primer required for DNA replication is: (1)
A. DNA polymerase
B. Primase
C. Helicase
D. Ligase
1.20. Apoptosis, or programmed cell death:
(1)
A. Is always a pathological process.
8. Causes inflammation and damage to surrounding tissues.
C. Is an orderly process important for normal development and tissue
homeostasis.
D. Is characterised by cell swelling and rupture.
QUESTION 2
[10)
Assess the following statements and decide whether they are TRUE OR FALSE. Write
only the number of the question and next to it TRUE or FALSE for each statement.
2.1. Lysosomes contain powerful hydrolytic enzymes that function best at acidic (1)
pH.
2.2. Exocytosis involves the fusion of vesicles with the plasma membrane to (1)
secrete substances out of the cell.
2.3. A protein with a hydrophobic stop-transfer sequence will remain as a (1)
transmembrane protein in the ER.
2.4. N-linked glycosylation involves the attachment of sugar groups to the amino (1)
group of asparagine residues in proteins.
2.5. The fluidity of a lipid bilayer decreases with an increase in the proportion of (1)
unsaturated fatty acid tails.
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CMBS21S • 1st OPPORTUNITY EXAMINATION PAPER
27 OCTOBER 2025
2.6. Ion-channel-coupled receptors are the slowest type of receptor in (1)
transmitting a signal.
2.7. lntegrins are cell adhesion molecules that primarily link the cytoskeleton to (1)
the extracellular matrix.
2.8 During mitosis, the nuclear envelope remains intact to protect the (1)
chromosomes.
2.9. DNA replication is described as semiconservative because each new DNA (1)
molecule contains one old strand and one new strand.
2.10. Transcription is the process where a sequence of DNA is copied into a (1)
complementary sequence of RNA.
SECTION B
QUESTION 3
[43)
3.1. List any FIVE organelles found in a typical eukaryotic cell and state one (5)
primary function for each.
3.2 Compare and contrast endocytosis and exocytosis.
(6)
3.3. Describe the role of the Signal Recognition Particle (SRP) in co-translational (6)
protein import into the ER.
3.4. Explain the difference between passive transport and active transport across (5)
a cell membrane, providing one example of each.
3.5. Using an example, briefly describe how a G-protein-coupled receptor (GPCR) (5)
can activate an intracellular signalling pathway.
3.6. Name the five phases of mitosis in order and describe one key event that (10)
occurs in each phase.
3.7. Differentiate between the leading strand and the lagging strand in DNA (6)
replication.
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CMB521S - 1st OPPORTUNITY EXAMINATION PAPER
SECTION D
27 OCTOBER 2025
(47}
QUESTION 4
[47]
Instructions: Answer the following questions in detail. Use diagrams where
appropriate to support your answer.
4.1. The Endomembrane System
4.1.1 Explain the structural and functional relationships between the endoplasmic {4}
reticulum (ER) and the Golgi apparatus
4.1.2 Describe the pathway and mechanisms a soluble protein would take from its (7)
synthesis on the rough ER to its secretion from the cell via exocytosis.
4.2. From DNA to Protein
Describe the process of gene expression, from the DNA sequence to a
functional protein.
4.2.1 Outline the key steps of transcription, including the enzyme responsible.
(8}
4.2.2 Outline the key steps of translation, including the roles of mRNA, tRNA, and {10)
ribosomes.
4.2.3 Explain one way in which gene expression can be regulated after (6)
transcription.
4.3. Cell Cycle and Cancer
4.3.1 Explain how apoptosis is a normal and essential biological process.
(4)
4.3.2 Discuss how a failure in the control mechanisms of the cell cycle (e.g., (8)
mutations in genes that regulate cell division) can lead to the uncontrolled
cell growth characteristic of cancer
END OF EXAMINATION
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