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Cell envelopes, membranes, walls, organelles, cytoskeleton and nucleus: NEET MCQs with answers

109 questions on this topic of Cell Structure and Function (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. Which of the following cellular organelles is NOT considered a part of the endomembrane system?

  1. Endoplasmic reticulum
  2. Peroxisome
  3. Golgi apparatus
  4. Vacuole
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Answer: (B) Peroxisome

The endomembrane system includes endoplasmic reticulum, Golgi complex, lysosomes, and vacuoles because their functions are coordinated. Functions of peroxisomes, mitochondria, and chloroplasts are not coordinated with these, hence they are not part of the endomembrane system.

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2. Ribosomes were first observed under the electron microscope as dense particles by:

  1. George Palade (1953)
  2. Robert Brown
  3. Camillo Golgi
  4. Singer and Nicolson
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Answer: (A) George Palade (1953)

George Palade first observed ribosomes as dense particles in 1953; they are made of RNA and proteins and are not surrounded by any membrane.

hard

3. In plant cells, the tonoplast helps transport ions and other materials into the vacuole:

  1. Against the concentration gradient, so their concentration is higher in the vacuole than in the cytoplasm
  2. Only by diffusion
  3. Out of the vacuole only
  4. Without any membrane proteins
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Answer: (A) Against the concentration gradient, so their concentration is higher in the vacuole than in the cytoplasm

The tonoplast facilitates transport of ions and other materials against concentration gradients into the vacuole. Hence their concentration is significantly higher in the vacuole than in the cytoplasm.

NCERT Class 11

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4. Select the INCORRECT statement regarding the middle lamella of plant cells:

  1. It is predominantly composed of calcium pectate.
  2. It holds or glues the different neighbouring cells together.
  3. It is laid down inner to the primary cell wall during cell division.
  4. It can be traversed by plasmodesmata that connect the cytoplasm of neighbouring cells.
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Answer: (C) It is laid down inner to the primary cell wall during cell division.

The middle lamella is the outermost layer laid down first between adjacent plant cells during cytokinesis (cell plate stage). The primary wall is formed internal to the middle lamella, not outer to it.

easy

5. Which layer of the plant cell wall is capable of growth in a young plant cell and gradually diminishes as the cell matures?

  1. Middle lamella
  2. Primary wall
  3. Secondary wall
  4. Tertiary wall
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Answer: (B) Primary wall

The primary wall of a young plant cell is capable of growth. As the cell matures, this capability gradually diminishes and the secondary wall is formed on the inner (towards membrane) side of the cell.

hard

6. Given below are two statements. Statement I: Mitochondria and chloroplasts contain their own DNA and 70S ribosomes. Statement II: Centrioles are found in almost all higher plant cells. Choose the correct answer.

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
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Answer: (B) Statement I is correct but Statement II is incorrect

Both organelles have circular DNA and 70S ribosomes. Centrioles are absent in almost all plant cells.

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7. Lysosomal hydrolytic enzymes are most active at:

  1. Neutral pH
  2. Any pH
  3. Alkaline pH
  4. Acidic pH
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Answer: (D) Acidic pH

Lysosomes are membrane-bound vesicles from the Golgi, rich in hydrolases (lipases, proteases, carbohydrases) that are optimally active at acidic pH.

NCERT Class 11

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8. Mitochondria are called the "power houses" of the cell because they:

  1. Package proteins
  2. Are the sites of aerobic respiration and produce energy as ATP
  3. Synthesise proteins
  4. Store starch
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Answer: (B) Are the sites of aerobic respiration and produce energy as ATP

Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP. The number per cell varies with the physiological activity of the cell.

NCERT Class 11

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9. In the human erythrocyte membrane, the approximate proportions of proteins and lipids are:

  1. 80% protein, 20% lipid
  2. 40% protein, 52% lipid
  3. 52% protein, 40% lipid
  4. 20% protein, 80% lipid
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Answer: (C) 52% protein, 40% lipid

Biochemical studies show the RBC membrane has about 52% protein and 40% lipids. The ratio varies between cell types.

NCERT Class 11

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10. In a dividing eukaryotic cell, specialized disc-shaped structures are found on the sides of the primary constriction of chromosomes. What are these structures called, and what is their primary function?

  1. Centrioles; serving as the anchor for nuclear pore complexes
  2. Kinetochores; serving as the sites of attachment of spindle fibres
  3. Chromomeres; responsible for transcription of ribosomal subunits
  4. Satellites; preventing the fusion of chromosome ends
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Answer: (B) Kinetochores; serving as the sites of attachment of spindle fibres

The primary constriction or centromere possesses disc-shaped structures called kinetochores. Spindle fibres attach to kinetochores during cell division to align and segregate chromosomes.

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11. Regarding the structure and function of the plant cell wall, select the CORRECT statement:

  1. The primary cell wall gradually diminishes in thickness as the cell matures.
  2. The secondary wall is formed on the outer side towards the middle lamella.
  3. Plasmodesmata traverse only the middle lamella and not the cell wall.
  4. Algal cell wall contains cellulose, hemicellulose, and pectin only.
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Answer: (A) The primary cell wall gradually diminishes in thickness as the cell matures.

In young growing plant cells, the primary wall is capable of extension, but as the cell reaches maturity, the primary wall diminishes while a secondary wall is laid down on the inner (cytoplasmic) side of the cell. Plasmodesmata traverse both cell wall and middle lamella.

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12. The outer membrane of the nuclear envelope:

  1. Is made of cellulose
  2. Is absent in animal cells
  3. Is continuous with the endoplasmic reticulum and bears ribosomes
  4. Has no pores
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Answer: (C) Is continuous with the endoplasmic reticulum and bears ribosomes

The nuclear envelope has two parallel membranes with a perinuclear space (10-50 nm). The outer membrane usually remains continuous with the ER and bears ribosomes.

NCERT Class 11

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