Cell Structure & Function MCQs set 3 for Army Medical College (AMC) Entry Test Biology — 20 solved questions.
Q1. A botanist compares the cell walls of a rose plant and a mushroom. What chemical component differentiates the mushroom's wall from the rose?
Answer: Chitin
Explanation: Chitin is the unique structural polysaccharide of fungal walls, whereas cellulose is the primary component of plant cell walls.
Q2. During an electron microscopy session, a student observes ribosomes inside a mitochondrion. What is the sedimentation coefficient of these specific ribosomes?
Answer: 70S
Explanation: Mitochondria contain 70S ribosomes, an anomaly within eukaryotic cells that typically possess 80S ribosomes in their cytosol.
Q3. A hematologist observes various human blood cells under a microscope. Which cell type represents a structural anomaly by lacking a nucleus at maturity?
Answer: Erythrocytes
Explanation: Mature mammalian erythrocytes lose their nuclei to maximize oxygen-carrying capacity, unlike leukocytes which remain nucleated throughout their lifespan.
Q4. While studying plant cell ultrastructure, a researcher identifies stacks of flattened sacs that function in secretion. What is the specific name for these units?
Answer: Dictyosomes
Explanation: In plant cells, the Golgi apparatus consists of individual stacks called dictyosomes, whereas animal cells usually have a single interconnected complex.
Q5. A student notices that the petals of a sunflower are bright yellow. Which specialized plastid is responsible for this non-green pigmentation?
Answer: Chromoplasts
Explanation: Chromoplasts contain carotenoid pigments like red and yellow, while chloroplasts are specifically green due to the dominance of chlorophyll.
Q6. A laboratory analysis compares the plasma membranes of E. coli and a human liver cell. Which lipid component is uniquely absent in the bacterial membrane?
Answer: Cholesterol
Explanation: Prokaryotic membranes lack sterols like cholesterol, which are essential for maintaining fluidity in eukaryotic plasma membranes.
Q7. A researcher isolates the protein subunits responsible for forming the spindle fibers during mitosis. Which specific protein makes up these hollow cylinders?
Answer: Tubulin
Explanation: Microtubules are composed of tubulin protein, while microfilaments consist of actin, though both are essential components of the cytoskeleton.
Q8. In a biochemical assay, a specific organelle is found to decompose hydrogen peroxide. Which enzyme is responsible for this protective reaction?
Answer: Catalase
Explanation: Peroxisomes contain catalase to decompose hydrogen peroxide into water and oxygen, protecting the cell from oxidative damage.
Q9. During the germination of castor bean seeds, stored lipids are rapidly converted into sugars. Which organelle facilitates this metabolic anomaly?
Answer: Glyoxysomes
Explanation: Glyoxysomes are specialized peroxisomes in germinating seeds that convert stored fats to carbohydrates, a process absent in animal cells.
Q10. A clinical report describes a patient with Pompe's disease, where glycogen accumulates in the liver. This condition results from a defect in which organelle?
Answer: Lysosomes
Explanation: Pompe's disease is caused by a lysosomal alpha-glucosidase deficiency, leading to glycogen buildup, unlike Tay-Sachs which involves lipid accumulation.
Q11. In striated muscle fibers, a specialized membrane system is responsible for the release and sequestration of calcium ions. Identify this organelle.
Answer: Smooth Endoplasmic Reticulum
Explanation: Sarcoplasmic reticulum is a specialized Smooth ER in muscle cells that regulates calcium ions, unlike the Rough ER which handles protein synthesis.
Q12. A cytologist observes that a secretory cell has 30,000 nuclear pores, while an undifferentiated cell has few. What determines this numerical variation?
Answer: Physiological activity of the cell
Explanation: Cells with high protein synthesis, like secretory cells, have a higher density of nuclear pores than inactive cells like erythrocytes.
Q13. During mitosis in a lily plant cell, a student notices the absence of centrioles. In which group of organisms is this absence a standard feature?
Answer: Angiosperms
Explanation: Higher plants lack centrioles and form spindle fibers through a different mechanism, whereas animal cells rely on centrioles for spindle organization.
Q14. A cell biologist notes that mitochondria can increase in number within a cell. Which structural feature directly supports their self-replicating ability?
Answer: Presence of circular DNA
Explanation: Mitochondria possess their own DNA and ribosomes, allowing them to self-replicate independently of the main cell cycle.
Q15. In a plant cell, the central vacuole maintains high internal osmotic pressure. What is the name of the specialized membrane regulating this transport?
Answer: Tonoplast
Explanation: The tonoplast is the selective membrane of the central vacuole that actively transports solutes against concentration gradients to maintain turgor.
Q16. Under a light microscope, a student observes the chloroplasts of an Elodea leaf moving in a circular path. What is this phenomenon called?
Answer: Cyclosis
Explanation: Cyclosis is the circular streaming movement of the cytosol, which helps in the distribution of nutrients and organelles within the cell.
Q17. A microbiologist discovers a prokaryote living in a hot spring whose cell wall does not contain peptidoglycan. To which group does it belong?
Answer: Archaebacteria
Explanation: Archaebacteria are unique prokaryotes that lack peptidoglycan, having walls made of proteins or other polysaccharides, unlike Eubacteria.
Q18. A researcher uses radioactive uracil to track RNA synthesis. Which non-membrane bound region within the nucleus will show the highest initial radioactivity?
Answer: Nucleolus
Explanation: The nucleolus is the site of ribosomal RNA synthesis and ribosome assembly, often associated with specific chromosomal regions called NORs.
Q19. During a tissue transplant, the recipient's immune system identifies the donor cells as foreign. Which surface structure is primarily responsible for this recognition?
Answer: Glycocalyx
Explanation: The glycocalyx, composed of glycolipids and glycoproteins, acts as a biological marker for cell-to-cell recognition and immune response.
Q20. An investigator examines the basal body (kinetosome) of a cilium. What specific microtubule arrangement will be found in this structure?
Answer: 9 triplets
Explanation: Centrioles and basal bodies have a 9+0 triplet microtubule arrangement, while the shaft of cilia/flagella has a 9+2 doublet arrangement.