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Cell: Structure and Functions: questions with answers

Class 11 Biology, Chapter 8 (NCERT). 15 questions by concept, 13 with pictures. Open “Show answer” for the answer and why.

How to teach this chapter · Common misconceptions & worked visual for this chapter

Cell as the unit of life, cell theory and cellular diversity

Question 1

An unlabelled cell outline is shown. Which interpretation of its branched form is sound?

?
  1. (a)Its branching is compatible with a specialised nerve-cell function; size alone cannot classify it.
  2. (b)All cells must have the same shape because they share a basic organisation.
  3. (c)Its branching has no relationship to function; apparent size alone still cannot classify it.
  4. (d)Its apparent size alone proves that it is prokaryotic.
Show answer

(a) Its branching is compatible with a specialised nerve-cell function; size alone cannot classify it.

Cells vary greatly in shape, and shape commonly reflects the function performed. Apparent size alone does not establish prokaryotic or eukaryotic organisation.

Question 2

A learner says, ‘Cell shape is unrelated to function, and a larger cell must be eukaryotic while a smaller one must be prokaryotic.’ Which correction is complete?

  1. (a)Neither form nor internal organisation can differ among cells.
  2. (b)Shape can reflect function, and structural organisation rather than size alone distinguishes the cell types.
  3. (c)Shape can reflect function, but size alone distinguishes prokaryotic and eukaryotic cells.
  4. (d)Shape is unrelated to function, but structural organisation rather than size alone distinguishes the cell types.
Show answer

(b) Shape can reflect function, and structural organisation rather than size alone distinguishes the cell types.

Cell shape commonly varies with the function performed. Size ranges overlap, so nuclear organisation and membrane-bound organelles—not size alone—separate the two cell organisations.

Prokaryotic cell organisation, envelope and surface structures

Question 3

Which interpretation of the unlabelled bacterial section is complete?

  1. (a)Envelope order is membrane-wall-glycocalyx; inward folds are mesosomes; free granules are non-membranous inclusions.
  2. (b)Envelope order is glycocalyx-wall-membrane; inward folds are separate membrane-bound organelles; free granules are non-membranous inclusions.
  3. (c)Envelope order is glycocalyx-wall-membrane; inward folds are mesosomes; reserve granules are membrane-bound inclusions.
  4. (d)Envelope order is glycocalyx-wall-membrane; inward folds are mesosomes; free granules are non-membranous inclusions.
Show answer

(d) Envelope order is glycocalyx-wall-membrane; inward folds are mesosomes; free granules are non-membranous inclusions.

The envelope runs glycocalyx, wall, membrane inward. Mesosomes are membrane infoldings in the source account, and reserve inclusions lie free without a bounding membrane.

Question 4

The unlabelled cell has a cell wall, an unbounded DNA region and particles whose subunits are 50S and 30S. Which interpretation is correct?

50S30S?
  1. (a)It is prokaryotic, lacks a nuclear membrane, and has 70S ribosomes.
  2. (b)It is prokaryotic but the visible particles cannot be ribosomes.
  3. (c)It is prokaryotic but the DNA region is enclosed by a nuclear membrane.
  4. (d)Its 50S and 30S subunits must form an 80S ribosome.
Show answer

(a) It is prokaryotic, lacks a nuclear membrane, and has 70S ribosomes.

An unbounded nucleoid and lack of membrane-bound organelles identify prokaryotic organisation. Its 50S and 30S ribosomal subunits form 70S, because sedimentation values are not additive.

Question 5

A learner says, ‘Capsule and slime are identical, pili drive motility, and a mesosome is a separate organelle.’ Which correction is complete?

  1. (a)Capsule and slime are identical; flagella cause motility; mesosomes are plasma-membrane infoldings.
  2. (b)Capsule is thick and slime loose; flagella cause motility; mesosomes are separate organelles.
  3. (c)Capsule is thick and slime loose; pili cause motility; mesosomes are plasma-membrane infoldings.
  4. (d)Capsule is thick and slime loose; flagella cause motility; mesosomes are plasma-membrane infoldings.
Show answer

(d) Capsule is thick and slime loose; flagella cause motility; mesosomes are plasma-membrane infoldings.

Capsule is thick and tough while slime is loose. Flagella mediate motility, and the source describes mesosomes as plasma-membrane infoldings.

Eukaryotic cell plan, plasma membrane and cell wall

Question 6

What do the surface circles and the arrow marked ? represent, and does the indicated movement require ATP?

?
  1. (a)Heads; water moving by osmosis; ATP required
  2. (b)Heads; water moving by osmosis; no ATP
  3. (c)Heads; solute moving by osmosis; no ATP
  4. (d)Tails; water moving by osmosis; no ATP
Show answer

(b) Heads; water moving by osmosis; no ATP

Hydrophilic heads face the aqueous sides and hydrophobic tails face inward. Water diffusion across a selectively permeable membrane is osmosis, while passive transport follows a gradient without ATP.

Question 7

Which interpretation of the unlabelled cell and wall junction is complete?

  1. (a)It is plant tissue; the middle lamella cements adjacent walls but the wall channels do not connect neighbouring cytoplasm.
  2. (b)It is animal tissue; the middle lamella cements adjacent walls and plasmodesmata connect the cytoplasm.
  3. (c)It is plant tissue; the plasma membrane is the cementing layer between walls and plasmodesmata connect the cytoplasm.
  4. (d)It is plant tissue; the middle lamella cements adjacent walls and plasmodesmata connect the cytoplasm.
Show answer

(d) It is plant tissue; the middle lamella cements adjacent walls and plasmodesmata connect the cytoplasm.

Only the plant profile has a wall. Between neighbouring plant walls, the calcium-pectate middle lamella cements them and plasmodesmata connect adjacent cytoplasm.

Endomembrane system: ER, Golgi, lysosomes and vacuoles

Question 8

The Golgi pathway diagram marks the opposite face from which modified material leaves with ?. Which complete interpretation is correct?

ER-derived vesicle?
  1. (a)Materials enter the cis face and leave from the trans face; lysosomes arise independently of Golgi and contain acidic hydrolases.
  2. (b)Materials enter the cis face and leave from the trans face; Golgi packaging forms lysosomes whose hydrolases work best at acidic pH.
  3. (c)Materials enter the trans face and leave from the cis face; Golgi packaging forms lysosomes whose hydrolases work best at acidic pH.
  4. (d)Materials enter the cis face and leave from the trans face; Golgi packaging forms lysosomes whose hydrolases work best at neutral pH.
Show answer

(b) Materials enter the cis face and leave from the trans face; Golgi packaging forms lysosomes whose hydrolases work best at acidic pH.

ER-derived vesicles fuse with the cis face, material moves toward and leaves from the trans face, and Golgi packaging forms lysosomes. Lysosomal hydrolases are optimally active at acidic pH.

Question 9

The diagram marks one ER region with ?. Which structure-function interpretation is correct?

?
  1. (a)smooth ER; specialised for secretory-protein synthesis
  2. (b)rough ER; specialised for secretory-protein synthesis
  3. (c)rough ER; specialised for lipid synthesis
  4. (d)smooth ER; specialised for lipid synthesis
Show answer

(d) smooth ER; specialised for lipid synthesis

The marked region is smooth ER because it has no attached ribosomes. SER is a major site of lipid synthesis.

Mitochondria, plastids and chloroplast architecture

Question 10

The chloroplast section marks one small particle in the surrounding compartment with ?. Which paired interpretation is correct?

?
  1. (a)Chlorophyll is present in thylakoids; chloroplast ribosomes are 80S.
  2. (b)Chlorophyll lies freely in the stroma; chloroplast ribosomes are 70S.
  3. (c)Chlorophyll lies freely in the stroma; chloroplast ribosomes are 80S.
  4. (d)Chlorophyll is present in thylakoids; chloroplast ribosomes are 70S.
Show answer

(d) Chlorophyll is present in thylakoids; chloroplast ribosomes are 70S.

Chlorophyll pigments are present in thylakoids, not freely in the stroma. Chloroplast ribosomes lie in the stroma and are 70S, smaller than the 80S cytoplasmic ribosomes.

Question 11

The mitochondrion diagram marks the narrow region between the two boundary membranes with ?. Which complete structural interpretation is correct?

?
  1. (a)Cristae are outer-membrane folds; matrix is enclosed by the inner membrane; intermembrane space lies between the two membranes.
  2. (b)Cristae are inner-membrane folds; matrix is enclosed by the inner membrane; intermembrane space lies between the two membranes.
  3. (c)Cristae are outer-membrane folds; matrix is the space between the inner and outer membranes; the inner compartment has no distinct name.
  4. (d)Cristae are inner-membrane folds; matrix is the space between the inner and outer membranes; the inner compartment has no distinct name.
Show answer

(b) Cristae are inner-membrane folds; matrix is enclosed by the inner membrane; intermembrane space lies between the two membranes.

Cristae are infoldings of the inner membrane. The matrix is the broad compartment enclosed by that membrane, whereas the intermembrane space is the narrow region between inner and outer membranes.

Ribosomes, cytoskeleton, cilia, flagella and centrioles

Question 12

The two cross-sections in the figure differ in their peripheral units and central elements. Which comparison is correct?

AB
  1. (a)A is a centriole with nine doublets and a central pair; B is an axoneme with nine peripheral triplets.
  2. (b)A is an axoneme shared by eukaryotic cilia and flagella; B is a centriole with nine peripheral triplets.
  3. (c)A is the axoneme of a cilium only; eukaryotic flagella have a different internal array; B is a centriole.
  4. (d)A and B are two views of the same array because paired and triple peripheral units can be swapped for each other.
Show answer

(b) A is an axoneme shared by eukaryotic cilia and flagella; B is a centriole with nine peripheral triplets.

Diagram A represents the 9+2 axoneme found in both eukaryotic cilia and flagella. Diagram B represents a centriole, whose nine peripheral fibrils are triplets and whose centre lacks the axonemal pair.

Question 13

A schematic shows several identical particles attached along one continuous strand and, separately, a branching network of filaments within a cell outline. Which interpretation is correct?

  1. (a)The particles are several non-membranous ribosomes on one mRNA; the branching structure is a protein-filament cytoskeleton.
  2. (b)The particles show several mRNAs on one ribosome; the branching structure is a protein-filament cytoskeleton.
  3. (c)The particles are membrane-bound ribosomes on one mRNA; the branching structure is a protein-filament cytoskeleton.
  4. (d)The particles are several ribosomes on one mRNA; the branching structure is an internal membrane system.
Show answer

(a) The particles are several non-membranous ribosomes on one mRNA; the branching structure is a protein-filament cytoskeleton.

The first structure represents a polysome: several non-membranous ribosomes translate one mRNA. The second represents the cytoskeleton, a proteinaceous filament network involved in support, motility and maintenance of cell shape.

Nucleus, chromatin and chromosome form

Question 14

In the chromosome detail, what does the structure marked ? represent?

?
  1. (a)secondary constriction
  2. (b)satellite
  3. (c)centromere
  4. (d)kinetochore
Show answer

(c) centromere

The marked structure is centromere. The centromere is the primary chromosome constriction, whereas kinetochores are paired disc-shaped structures on its sides.

Question 15

The ? marks a spherical body in the nucleoplasm. Which statement correctly describes its relation to the surrounding nucleoplasm?

?
  1. (a)It is an extended nucleoprotein fibre that becomes a chromosome during division.
  2. (b)It is a gap formed by fusion of the two nuclear-envelope membranes.
  3. (c)Its contents are continuous with the rest of the nucleoplasm.
  4. (d)Its contents are separated from nucleoplasm by a membrane.
Show answer

(c) Its contents are continuous with the rest of the nucleoplasm.

The marked body is the nucleolus. Its contents are continuous with the rest of the nucleoplasm. It is a site of active ribosomal RNA synthesis.

Common misconception in Cell: Structure and Functions

Open full misconception guide →

Can cells without a nucleus make proteins?

Wrong

A bacterium has no ribosomes because it lacks a nucleus.

Why it feels right. I treat every cell structure as if it needs a membrane compartment.

Right

Bacteria have non-membrane-bound ribosomes in the cytoplasm.

Worked example

The bacterial DNA lies in a nucleoid. Separate 70S ribosomes in the cytoplasm make proteins.
  1. In a bacterial cell, the DNA sits in a nucleoid without a nuclear membrane.
  2. The separate 70S ribosomes in the cytoplasm translate RNA to make proteins.