Part 6 — Cytoskeleton, Cilia, Flagella, Centrioles, Ultrastructure & Specialized Functions (Q126–150)

Part 6 — Cytoskeleton, Cilia, Flagella, Centrioles, Ultrastructure & Specialized Functions (Q126–150)

Q126.

Which proteins form microfilaments?
A. Tubulin
B. Actin ✅
C. Keratin
D. Myosin

Explanation:

• A. Tubulin: Forms microtubules.
• B. Actin (Correct): Microfilaments are polymers of actin.
• C. Keratin: Intermediate filaments.
• D. Myosin: Motor protein, not structural filament.

Q127.

Microtubules are made up of:
A. Tubulin ✅
B. Actin
C. Lamin
D. Collagen

Explanation:

• A. Tubulin (Correct): Microtubules are hollow tubes of α- and β-tubulin.
• B. Actin: For microfilaments.
• C. Lamin: Intermediate filament in nuclear lamina.
• D. Collagen: Extracellular protein, not cytoskeleton.

Q128.

Intermediate filaments provide:
A. ATP production
B. Tensile strength and mechanical support ✅
C. Vesicle transport
D. Photosynthesis

Explanation:

• A. ATP: Mitochondria.
• **B. Correct — keratin, vimentin give structural support, resist stress.
• **C. Transport = microtubules.
• **D. Photosynthesis: chloroplasts.

Q129.

The cytoskeleton is absent in:
A. Prokaryotes ✅
B. Protozoa
C. Fungi
D. Animal cells

Explanation:

• **A. Correct — prokaryotes lack complex cytoskeleton (though some proteins are cytoskeleton-like).
• **B. Protozoa: present.
• **C. Fungi: present.
• **D. Animal cells: present.

Q130.

The beating of cilia/flagella is powered by:
A. ATP hydrolysis by dynein arms ✅
B. Passive diffusion
C. RNA synthesis
D. DNA replication

Explanation:

• **A. Correct — dynein arms hydrolyze ATP → sliding of microtubules.
• **B. Not passive.
• **C. RNA synthesis unrelated.
• **D. DNA replication unrelated.

Q131.

The typical axoneme structure of motile cilia is:
A. 9 + 0
B. 9 + 2 ✅
C. 9 + 1
D. 13 + 2

Explanation:

• A. 9 + 0: Found in centrioles.
• B. 9 + 2 (Correct): Nine outer doublets + two central singlets.
• C. 9 + 1: Not found.
• D. 13 + 2: Not valid.

Q132.

Basal bodies of cilia are structurally similar to:
A. Centrioles ✅
B. Ribosomes
C. Nucleolus
D. Lysosomes

Explanation:

• A. Centrioles (Correct): Both have 9 triplet microtubule arrangement.
• B. Ribosomes: Non-membranous.
• C. Nucleolus: rRNA synthesis, not structural.
• D. Lysosomes: Single membrane.

Q133.

Which motor protein is essential for microtubule sliding in flagella?
A. Kinesin
B. Dynein ✅
C. Myosin
D. Tubulin

Explanation:

• A. Kinesin: Intracellular transport.
• B. Dynein (Correct): Flagellar movement.
• C. Myosin: Actin motor.
• D. Tubulin: Structural protein.

Q134.

Which structure acts as microtubule-organizing center in animal cells?
A. Golgi body
B. Centrosome ✅
C. Nucleolus
D. Ribosome

Explanation:

• A. Golgi: Protein packaging.
• B. Centrosome (Correct): Contains centrioles, organizes spindle.
• C. Nucleolus: Ribosome synthesis.
• D. Ribosome: Protein synthesis.

Q135.

Centrioles are made of:
A. 9 triplet microtubules ✅
B. 9 doublet microtubules + 2 central
C. 13 protofilaments
D. Actin filaments

Explanation:

• **A. Correct — centriole = 9 triplets, no central pair.
• **B. 9 + 2 = axoneme.
• **C. 13 protofilaments = structure of each microtubule, not centriole.
• **D. Actin = microfilaments.

Q136.

Centrioles are absent in:
A. Animal cells
B. Algae
C. Higher plant cells ✅
D. Protozoa

Explanation:

• **A. Animals: present.
• **B. Many algae: present.
• C. Higher plants (Correct): No centrioles, spindle forms differently.
• **D. Protozoa: present.

Q137.

Cilia and flagella differ mainly in:
A. Chemical composition
B. Length and beating pattern ✅
C. Presence of tubulin
D. Presence of dynein

Explanation:

• **A. Same composition.
• **B. Correct — cilia short, beat rapidly; flagella longer, wave-like motion.
• **C. Tubulin in both.
• **D. Dynein in both.

Q138.

The centrosome is located:
A. Inside nucleus
B. Near nucleus in cytoplasm ✅
C. Inside chloroplast
D. In vacuole

Explanation:

• **A. Not inside nucleus.
• **B. Correct — near nucleus, organizes spindle.
• **C. Not chloroplast.
• **D. Not vacuole.

Q139.

Which cytoskeletal element helps in chromosome movement during cell division?
A. Microfilaments
B. Microtubules ✅
C. Intermediate filaments
D. Tonoplast

Explanation:

• A. Microfilaments: Cytokinesis.
• B. Microtubules (Correct): Form spindle fibers → chromosome separation.
• **C. Intermediate filaments: structural support.
• **D. Tonoplast: vacuole membrane.

Q140.

Primary cilia in vertebrates are mostly:
A. Motile
B. Non-motile sensory structures ✅
C. Absent
D. Photosynthetic

Explanation:

• A. Motile: Most are not.
• **B. Correct — primary cilia act as sensory organelles (9 + 0 axoneme).
• **C. Not absent.
• **D. No photosynthesis.

Q141.

Which organelle anchors the base of cilia/flagella?
A. Centriole (basal body) ✅
B. Ribosome
C. Lysosome
D. Peroxisome

Explanation:

• **A. Correct — basal bodies = modified centrioles anchor axoneme.
• **B. Ribosomes: protein synthesis.
• **C. Lysosomes: digestion.
• **D. Peroxisome: detoxification.

Q142.

During cytokinesis in animal cells, the cleavage furrow is formed by:
A. Actin filaments ✅
B. Microtubules
C. Intermediate filaments
D. Dynein

Explanation:

• **A. Correct — actin + myosin contractile ring pinches cell.
• **B. Spindle fibers, not cleavage.
• **C. Structural support only.
• **D. Dynein: flagellar motion.

Q143.

Cilia in respiratory tract help in:
A. Gas exchange
B. Transport of mucus and dust ✅
C. ATP production
D. Protein synthesis

Explanation:

• **A. Gas exchange = alveoli.
• **B. Correct — beat to move mucus + trapped dust.
• **C. ATP production = mitochondria.
• **D. Protein synthesis = ribosomes.

Q144.

Which cytoskeletal element forms the spindle apparatus?
A. Actin
B. Microtubules ✅
C. Collagen
D. Myosin

Explanation:

• **A. Actin: cleavage furrow.
• B. Microtubules (Correct): Form spindle fibers.
• **C. Collagen: extracellular.
• **D. Myosin: motor, not spindle.

Q145.

Which cytoskeletal system provides tracks for organelle movement?
A. Microtubules ✅
B. Microfilaments only
C. Intermediate filaments
D. None

Explanation:

• **A. Correct — microtubules + motor proteins transport vesicles.
• **B. Microfilaments also assist, but major tracks = microtubules.
• **C. Intermediate filaments: stability.
• **D. Not true.

Q146.

The cilia/flagella membrane is continuous with:
A. Endoplasmic reticulum
B. Plasma membrane ✅
C. Nuclear envelope
D. Golgi

Explanation:

• **A. Not connected to ER.
• **B. Correct — outer membrane continuous with plasma membrane.
• **C. Nuclear envelope unrelated.
• **D. Golgi: packaging.

Q147.

Which cytoskeletal element is most stable and provides structural integrity?
A. Microtubules
B. Microfilaments
C. Intermediate filaments ✅
D. Actomyosin

Explanation:

• **A. Microtubules: dynamic.
• **B. Microfilaments: dynamic.
• C. Intermediate filaments (Correct): Provide mechanical strength, less dynamic.
• **D. Actomyosin: contractile complex.

Q148.

Which is NOT true of centrioles?
A. Help in spindle formation
B. Have 9 triplet microtubules
C. Found in higher plants ✅
D. Form basal bodies of cilia

Explanation:

• **A. True.
• **B. True.
• **C. Correct — absent in higher plants.
• **D. True — basal bodies are derived from centrioles.

Q149.

Which structure connects adjacent cells in animal tissues for communication?
A. Tight junction
B. Gap junction ✅
C. Desmosome
D. Plasmodesmata

Explanation:

• **A. Tight junction: sealing.
• B. Gap junction (Correct): Channels for ions/small molecules.
• **C. Desmosome: adhesion.
• **D. Plasmodesmata: plants, not animals.

Q150.

The arrangement of microtubules in centrioles is:
A. 9 + 2
B. 9 triplets + none central ✅
C. 13 protofilaments + 2
D. 7 + 1

Explanation:

• **A. 9 + 2: cilia/flagella.
• **B. 9 triplets without central (Correct).
• **C. Protofilaments apply to microtubules, not centriole structure.
• **D. Not valid.

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