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20. A cell has no nucleus, no mitochondria, and ribosomes smaller than those in eukaryotes. What type of cell is it? a) Plant cell b) Animal cell c) Bacterial cell d) Fungal cell Answer: 20. c) Bacterial cell

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Case-Based Exam: Cell Biology Scenario: Scientists discover a new organelle in liver cells that breaks down toxic compounds. It has a smooth membrane and contains enzymes similar to those in peroxisomes. 1. What is the most likely function of this organelle? a) ATP production b) Detoxification c) Protein synthesis d) Photosynthesis 2. Which existing organelle does it resemble? a) Rough ER b) Smooth ER c) Mitochondria d) Chloroplast Answers: 1. b) Detoxification 2. b) Smooth ER --- Scenario: A plant cell is placed in a hypertonic sugar solution. Over time, the cell membrane pulls away from the cell wall. 3. What is this process called? a) Turgidity b) Plasmolysis c) Lysis d) Hemolysis 4. What would happen if the cell were placed in pure water afterward? a) It would burst b) It would regain turgor pressure c) It would remain shriveled d) It would divide Answers: 3. b) Plasmolysis 4. b) It would regain turgor pressure --- Scenario: A DNA mutation changes a codon from "GAA" to "GAG." Both codons code for glutamic acid. 5. What type of mutation is this? a) Missense b) Nonsense c) Silent d) Frameshift 6. Why does this mutation not affect the protein? a) The amino acid sequence changes b) The codon still codes for the same amino acid c) The mutation is repaired by enzymes d) The ribosome ignores the mutation Answers: 5. c) Silent 6. b) The codon still codes for the same amino acid --- Scenario: A pancreatic cell produces large amounts of insulin, a protein hormone. 7. Which organelle would be MOST abundant in this cell? a) Chloroplast b) Rough ER c) Lysosome d) Nucleolus 8. How does insulin leave the cell? a) Osmosis b) Exocytosis c) Active transport d) Diffusion Answers: 7. b) Rough ER 8. b) Exocytosis --- Scenario: A muscle cell runs out of oxygen during intense exercise. It continues producing ATP but accumulates lactic acid. 9. What process is the cell using to make ATP? a) Aerobic respiration b) Fermentation c) Photosynthesis d) Glycolysis only 10. Why does lactic acid build up? a) Oxygen is required to break it down b) It is a byproduct of anaerobic respiration c) The mitochondria are damaged d) The cell membrane leaks Answers: 9. b) Fermentation 10. b) It is a byproduct of anaerobic respiration --- Scenario: A diagram shows a cell with chromosomes lined up at the equator during mitosis. 14. Which phase is shown? a) Prophase b) Metaphase c) Anaphase d) Telophase 15. What structure attaches to the chromosomes to pull them apart? a) Centrioles b) Spindle fibers c) Nuclear envelope d) Cell plate Answers: 14. b) Metaphase 15. b) Spindle fibers --- Scenario: A student wants to test how temperature affects enzyme activity. 16. What is the independent variable? a) Enzyme concentration b) Temperature c) Substrate type d) pH level 17. What control should be used? a) A test tube with no enzyme b) A test tube at room temperature c) A test tube with double the enzyme d) A test tube with no substrate Answers: 16. b) Temperature 17. b) A test tube at room temperature --- Scenario: In Ethiopia’s lowlands, malaria parasites invade red blood cells (RBCs), causing them to burst. 18. Which organelle do the parasites target to burst RBCs? a) Nucleus b) Lysosome c) Cell membrane d) Vacuole 19. Why does this cause fever in patients? a) Toxins are released b) Oxygen levels drop c) White blood cells overreact d) The spleen enlarges Answers: 18. c) Cell membrane 19. a) Toxins are released ---

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situational biology questions similar to what might appear in the ESSLCE Biology exam, designed to test analytical and application skills: --- Infectious Disease Outbreak Scenario: In a rural Ethiopian village, several people developed fever, chills, and anemia. Health workers observed that symptoms worsened after rainy seasons and found *Plasmodium* parasites in blood samples. 1. What disease is this? a) Tuberculosis b) Malaria c) Typhoid d) HIV/AIDS 2. How is this disease transmitted? a) Contaminated water b) Mosquito bites c) Airborne droplets d) Physical contact 3. Which preventive measure is MOST effective? a) Vaccination b) Antibiotics c) Bed nets d) Handwashing

Answer Key: 1. b) Malaria 2. b) Mosquito bites 3. c) Bed nets

--- Ecosystem Disruption Scenario: A farmer cleared a forest to grow crops. Over time, soil fertility declined, nearby rivers silted up, and native bird populations disappeared. 4. What is the immediate cause of soil erosion here? a) Overgrazing b) Deforestation c) Climate change d) Pesticide use 5. Which conservation method would BEST restore biodiversity? a) Monoculture farming b) Terracing c) Reforestation d) Using chemical fertilizers

Answer Key: 4. b) Deforestation 5. c) Reforestation

--- Genetic Disorder Scenario: A couple has three children. Two are healthy, but one has sickle-cell anemia (a recessive genetic disorder). Both parents are unaffected. 6. What are the parents’ genotypes? a) AA × AA b) AA × Aa c) Aa × Aa d) aa × aa 7. What is the probability their next child will have the disease? a) 0% b) 25% c) 50% d) 100%

Answer Key: 6. c) Aa × Aa 7. b) 25%

--- Human Physiology Scenario: An athlete collapsed during a marathon. Medical tests showed severe dehydration, low sodium levels, and muscle cramps. 8. Which condition is this? a) Heat stroke b) Diabetes c) Hypertension d) Anemia 9. What is the FIRST aid treatment? a) Give sugary drinks b) Administer insulin c) Provide electrolyte fluids d) Wrap in warm blankets

Answer Key: 8. a) Heat stroke 9. c) Provide electrolyte fluids

--- Plant Experiment Scenario: A student planted two bean seeds: - Pot A: Watered daily, placed in sunlight. - Pot B: Watered daily, kept in a dark closet. After 2 weeks, Pot A grew 15 cm tall; Pot B grew 2 cm tall with yellow leaves. 10. Why did Pot B grow poorly? a) Lack of oxygen b) Absence of photosynthesis c) Too much water d) Poor soil quality 11. What is the independent variable in this experiment? a) Amount of water b) Type of seed c) Light exposure d) Soil type Answer Key:

10. b) Absence of photosynthesis 11. c) Light exposure

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