Chapter 8: Cell: The Unit of Life Application Questions | biology Class 11 CBSE

ByteNotes

Chapter 8: Cell: The Unit of Life Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A student observes that the cells of a particular tissue in a factory-farmed chicken are unusually large and contain an extraordinary number of mitochondria. With reference to cell biology, explain why this might be the case.

Mitochondria are the powerhouses of the cell, responsible for producing ATP through aerobic respiration; cells with high energy demands require more mitochondria.
The tissue is likely muscle tissue involved in continuous or intense activity; muscle cells require high ATP to fuel contraction, hence more mitochondria are present.
The number of mitochondria per cell varies depending on the physiological activity of the cell — highly active cells accumulate more mitochondria to meet energy demands.
This illustrates the principle that cell structure is adapted to function: energy-intensive cells are characterised by increased mitochondrial density as a direct response to metabolic requirements.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A bacterium causes infection by attaching to host intestinal cells. With reference to prokaryotic surface structures, explain which structures facilitate this attachment and how.

Fimbriae are small bristle-like fibres sprouting from the bacterial cell surface that help certain bacteria attach to host tissues, including intestinal epithelial cells.
Pili are elongated tubular protein structures that can also facilitate attachment to host cells and assist in the transfer of genetic material during conjugation.
The glycocalyx (especially the capsule form) can also contribute to adhesion by protecting the bacterium and helping it adhere to surfaces.
These attachment structures are critical for pathogenicity — without the ability to anchor to host tissues, bacteria cannot colonise, multiply, and cause infection.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 3

Applied Concept

A cell biologist treats pancreatic acinar cells (which secrete digestive enzymes) with a drug that disrupts the Golgi apparatus. Predict the cellular consequences and justify your answer.

Pancreatic acinar cells are secretory cells that rely on the Golgi apparatus to package digestive enzymes into vesicles for exocytosis into the pancreatic duct.
Disruption of the Golgi apparatus would block the modification (e.g., glycosylation) and packaging of proteins synthesised by the RER into exportable vesicles.
Secretory vesicles would fail to form at the trans face of the Golgi, preventing the release of digestive enzymes from the cell.
As a result, digestive enzyme secretion would cease, proteins would accumulate in the ER or cytoplasm, and the endomembrane secretory pathway would be completely disrupted.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 4

Applied Concept

With reference to the fluid mosaic model, explain why a cell membrane maintains its integrity even as proteins constantly move within it.

In the fluid mosaic model (Singer and Nicolson, 1972), the phospholipid bilayer has a quasi-fluid nature that allows lateral movement of proteins without disrupting the membrane as a whole.
The hydrophobic tails of phospholipids face inward and the polar heads face outward; this arrangement maintains bilayer stability while allowing individual molecules to move laterally.
Integral and peripheral proteins are embedded in or associated with this fluid bilayer and can shift position; cholesterol in the membrane further regulates fluidity by preventing it from becoming too rigid or too fluid.
The overall mosaic structure — a sea of lipids with embedded protein 'islands' — ensures functional integrity is preserved even during constant protein movement essential for processes like endocytosis and cell signalling.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 5

Applied Concept

A plant cell is placed in a very concentrated sugar solution. Using your knowledge of osmosis and the tonoplast, explain what would happen to the cell's central vacuole.

When a plant cell is placed in a concentrated (hypertonic) solution, water moves out of the cell by osmosis — from a region of higher water potential (inside) to lower water potential (outside).
The central vacuole, bounded by the tonoplast, loses water as the tonoplast facilitates its movement; the vacuole shrinks as turgor pressure decreases.
As the vacuole contracts, the cytoplasm and plasma membrane pull away from the rigid cell wall — a process called plasmolysis.
The tonoplast (vacuolar membrane) is selectively permeable and plays a key role in regulating ion and water transport; its structural integrity is maintained even as the vacuole shrinks, though prolonged water loss can be lethal to the cell.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 6

Applied Concept

A researcher discovers a new antibiotic that specifically targets 70S ribosomes. Explain why this antibiotic would be effective against bacteria but not harmful to human cells.

Bacterial (prokaryotic) ribosomes are 70S, composed of 50S and 30S subunits; this size is fundamentally different from the 80S ribosomes (60S + 40S) found in human (eukaryotic) cytoplasm.
An antibiotic targeting 70S ribosomes would inhibit bacterial protein synthesis by binding to the 50S or 30S subunit, preventing translation and killing the bacteria.
Human cytoplasmic ribosomes are 80S and structurally distinct; the antibiotic would not bind to them, leaving human protein synthesis unaffected.
However, the ribosome-containing organelles in human cells (mitochondria have 70S ribosomes) could potentially be affected, which is why some antibiotics have minor mitochondrial side effects — but overall therapeutic selectivity is retained.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

A student notices that cells lining the small intestine have numerous finger-like projections on their surface. With reference to the plasma membrane and cell functions, explain the significance of these projections.

The finger-like projections (microvilli) increase the surface area of the plasma membrane dramatically, maximising contact between the cell and the intestinal contents.
Greater surface area means more membrane surface is available for the transport proteins and carrier molecules that facilitate absorption of nutrients by facilitated diffusion and active transport.
Active transport across the intestinal cell membrane (e.g., glucose absorption against its gradient using ATP) is greatly enhanced by the increased number of transporter proteins spread across the larger membrane area.
This structural adaptation illustrates a fundamental cellular principle: cells specialised for absorption or secretion maximise their functional membrane area through surface projections.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 8

Applied Concept

With reference to the cell theory, explain whether viruses should be considered living organisms.

The cell theory states that all living organisms are composed of cells and their products, and all cells arise from pre-existing cells.
Viruses are acellular (non-cellular) entities — they consist only of a nucleic acid core surrounded by a protein coat and cannot carry out independent metabolism or reproduce without a host cell.
Since viruses are not composed of cells, they do not satisfy the first postulate of cell theory; they also cannot reproduce by cell division, violating the second postulate.
Therefore, by the criteria of cell theory, viruses are not considered living organisms — they are classified as entities at the boundary of living and non-living, dependent entirely on host cellular machinery for replication.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 9

Applied Concept

A plant grown in a region with high light intensity shows leaves with a large number of well-developed chloroplasts per mesophyll cell. Explain this observation in terms of chloroplast structure and function.

Chloroplasts trap light energy through chlorophyll and carotenoid pigments located in thylakoid membranes of grana; more light intensity means more light energy available for photosynthesis.
Cells under high light conditions develop more chloroplasts (20–40 per mesophyll cell) to exploit the abundant light; more chloroplasts provide more thylakoid surface area for light reactions.
The stroma of each chloroplast contains the enzymes for the Calvin cycle; more chloroplasts means more enzymatic capacity for carbon fixation and carbohydrate synthesis.
This represents a direct structural adaptation to environmental conditions — the cell responds to light availability by increasing the number of light-harvesting organelles, maximising photosynthetic yield.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 10

Applied Concept

A genetic disease causes lysosomes to lack functional hydrolytic enzymes. Predict the cellular consequences and explain your reasoning using knowledge of lysosome function.

Lysosomes contain hydrolytic enzymes (lipases, proteases, carbohydrases) active at acidic pH that are responsible for digesting macromolecules including old organelles, foreign material, and cellular debris.
If hydrolytic enzymes are absent or non-functional, cellular waste products, damaged organelles, and engulfed materials would accumulate within the lysosomes instead of being broken down.
This accumulation, seen in lysosomal storage diseases, causes lysosomes to swell, impairing their function and causing cellular dysfunction; affected cells may eventually die.
The inability to recycle cellular components also deprives the cell of building blocks (amino acids, lipids, sugars) for biosynthesis, further compromising cellular metabolism and survival.

ByteNotes

Premium Access

Unlock all Application Questions

You are viewing 10 free application questions from this chapter. Upgrade to Premium to unlock the remaining 11 questions.

Upgrade to Premium11 questions locked

Chapter sections

Chapter 8: Cell: The Unit of Life | Application Questions

A student observes that the cells of a particular tissue in a factory-farmed chicken are unusually large and contain an extraordinary number of mitochondria. With reference to cell biology, explain why this might be the case.

A bacterium causes infection by attaching to host intestinal cells. With reference to prokaryotic surface structures, explain which structures facilitate this attachment and how.

A cell biologist treats pancreatic acinar cells (which secrete digestive enzymes) with a drug that disrupts the Golgi apparatus. Predict the cellular consequences and justify your answer.

With reference to the fluid mosaic model, explain why a cell membrane maintains its integrity even as proteins constantly move within it.

A plant cell is placed in a very concentrated sugar solution. Using your knowledge of osmosis and the tonoplast, explain what would happen to the cell's central vacuole.

A researcher discovers a new antibiotic that specifically targets 70S ribosomes. Explain why this antibiotic would be effective against bacteria but not harmful to human cells.

A student notices that cells lining the small intestine have numerous finger-like projections on their surface. With reference to the plasma membrane and cell functions, explain the significance of these projections.

With reference to the cell theory, explain whether viruses should be considered living organisms.

A plant grown in a region with high light intensity shows leaves with a large number of well-developed chloroplasts per mesophyll cell. Explain this observation in terms of chloroplast structure and function.

A genetic disease causes lysosomes to lack functional hydrolytic enzymes. Predict the cellular consequences and explain your reasoning using knowledge of lysosome function.

Unlock all Application Questions