Practice Cell Structure & Function MCQs for MDCAT (Medical & Dental) Biology — topic-wise sets with solved answers.
Q1. During the cytokinesis of a plant cell, a student identifies the first layer to be deposited between the two newly formed daughter cells.
Answer: Middle lamella
Explanation: Middle lamella is the first layer formed during cytokinesis; the primary wall is tempting but it develops after the middle lamella.
Q2. A researcher analyzing the plasma membrane identifies a conjugate molecule consisting of a carbohydrate covalently bonded to a lipid.
Answer: Glycolipids
Explanation: Glycolipids are carbohydrate-lipid conjugates; glycoproteins are tempting but involve proteins rather than lipids as the base molecule.
Q3. While observing a staining pattern in a eukaryotic nucleus, a technician notices a non-membranous, dense body responsible for rRNA synthesis.
Answer: Nucleolus
Explanation: The nucleolus is the site of ribosomal RNA synthesis; the chromatin is tempting but it contains the genetic blueprints instead.
Q4. A biochemist isolates ribosomes from a human liver cell and determines the sedimentation coefficients of their two distinct subunits.
Answer: 40S and 60S
Explanation: Eukaryotic ribosomes consist of 40S and 60S subunits; 30S and 50S are tempting but are specific to prokaryotic cells.
Q5. In a patient suffering from drug overdose, which organelle in the liver cells would be most active in detoxifying the harmful chemicals?
Answer: Smooth Endoplasmic Reticulum
Explanation: SER is primarily responsible for detoxification in the liver; RER is tempting but focuses on protein synthesis instead.
Q6. A student examines the Golgi apparatus under an electron microscope and identifies a stack of flattened, membrane-bound sacs.
Answer: Cisternae
Explanation: Cisternae are the flattened sacs of the Golgi; cristae are tempting but are the folds of the mitochondrial inner membrane.
Q7. A lab technician isolates an organelle and finds it contains a high concentration of hydrolytic enzymes, specifically acid phosphatases.
Answer: Acid phosphatases
Explanation: Acid phosphatases are characteristic hydrolytic enzymes in lysosomes; ATPases are tempting but are involved in energy transport.
Q8. During a cellular study, an organelle is found to contain oxidases that produce hydrogen peroxide and catalases that break it down.
Answer: Peroxisomes
Explanation: Peroxisomes contain catalase to decompose hydrogen peroxide; glyoxysomes are tempting but are found in germinating fatty seeds.
Q9. A structural analysis of a xylem vessel reveals a thick cell wall layer containing cellulose, hemicellulose, and significant amounts of lignin.
Answer: Secondary wall
Explanation: Secondary cell walls contain lignin for strength; primary walls are tempting but are mainly composed of cellulose and pectin.
Q10. In the fluid mosaic model, a specific class of proteins is observed to be deeply embedded or spanning the phospholipid bilayer.
Answer: Integral proteins
Explanation: Integral proteins are partially or fully embedded in the bilayer; peripheral proteins are tempting but only stay on the surface.
Q11. An undifferentiated cell shows high metabolic activity. Approximately how many nuclear pores would you expect to find on its nuclear envelope?
Answer: Up to 30,000 pores
Explanation: Nuclear pore count correlates with cellular activity; 30,000 is for active cells, while 3-4 is for inactive ones like erythrocytes.
Q12. During rapid protein synthesis in a muscle cell, several ribosomes are seen attached to a single strand of messenger RNA.
Answer: Polysome
Explanation: A polysome is a cluster of ribosomes on one mRNA; a phagosome is tempting but refers to an engulfed food particle.
Q13. A cell is observed recycling its own old and non-functional mitochondria by enclosing them in a lysosomal vacuole.
Answer: Autophagy
Explanation: Autophagy is the self-digestion of organelles; phagocytosis is tempting but involves the engulfment of external foreign particles.
Q14. In a germinating castor bean seed, which organelle is responsible for converting stored fatty acids into succinate via the glyoxylate cycle?
Answer: Glyoxysomes
Explanation: Glyoxysomes convert fatty acids to succinate; peroxisomes are tempting but primarily handle photorespiration and detoxification.
Q15. An electron micrograph of a mitochondrion shows numerous inner membrane folds that maximize the site for aerobic respiration and ATP production.
Answer: Cristae
Explanation: Cristae increase surface area for the electron transport chain; the matrix is tempting but is the fluid-filled interior space.
Q16. In a chloroplast, the green pigment chlorophyll is located within stacks of flattened sacs known as what?
Answer: Grana
Explanation: Grana are stacks of thylakoids; stroma is tempting but it is the fluid surrounding the thylakoid stacks.
Q17. During mitosis, long unbranched hollow cylinders made of tubulin protein assemble to form the mitotic spindle. These structures are:
Answer: Microtubules
Explanation: Microtubules are composed of tubulin and form the spindle; microfilaments are tempting but are made of actin for movement.
Q18. A child is diagnosed with a lysosomal storage disorder characterized by the accumulation of lipids (gangliosides) in the brain, leading to mental retardation.
Answer: Tay-Sachs disease
Explanation: Tay-Sachs involves lipid accumulation in brain cells; Gaucher's is tempting but involves different lipid types and systemic symptoms.
Q19. Which component of the cytoskeleton has the smallest diameter and is primarily involved in internal cellular movements like cyclosis?
Answer: Microfilaments
Explanation: Microfilaments are 7nm, microtubules 25nm; intermediate filaments are tempting as they are 'intermediate' at 8-10nm.
Q20. A microbiologist analyzes the cell wall of an Escherichia coli bacterium. Which strengthening polymer is uniquely found in this structure?
Answer: Peptidoglycan
Explanation: Peptidoglycan (murein) is the prokaryotic cell wall polymer; chitin is tempting but is found in fungal cell walls.
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