Cytoskeleton Notes for NEET | Microtubules, Microfilaments & Cell Structure Explained

 

Cytoskeleton – Easy Notes for NEET 

Cytoskeleton structure showing microtubules, microfilaments, and intermediate filaments inside a cell.

- Dr.Sanjaykumar Pawar 

Definition

• Cytoskeleton is a network of protein fibres present in the cytoplasm of a cell.
• It forms the internal framework or "skeleton" of the cell.
• It is made up of filamentous (thread-like) protein structures.

Components of Cytoskeleton The cytoskeleton consists of three main types of fibres:

1. Microtubules

   • Long, hollow, tube-like structures.
   • Made of the protein tubulin.
   • Help in cell division and movement of cell organelles.

2. Microfilaments

   • Thin, solid fibres.
   • Made of the protein actin.
   • Help in cell movement and change in cell shape.

3. Intermediate Filaments

   • Fibres of intermediate thickness.
   • Provide strength and stability to the cell.
   • Help the cell resist mechanical stress.

Location

• Present throughout the cytoplasm of eukaryotic cells.
• Forms a supporting network inside the cell.

Functions of Cytoskeleton

1. Mechanical Support

   • Provides internal support to the cell.
   • Prevents the cell from collapsing.

2. Maintenance of Cell Shape

   • Gives a definite shape to the cell.
   • Helps the cell maintain its structure.

3. Cell Motility (Movement)

   • Assists in movement of the whole cell.
   • Helps in movements such as amoeboid movement and muscle contraction.

4. Movement of Cell Organelles

   • Helps organelles move from one part of the cell to another.

5. Role in Cell Division

   • Microtubules form spindle fibres during cell division.
   • Ensures proper distribution of chromosomes.

NEET Important Points

• Cytoskeleton = Network of protein fibres in cytoplasm.
• Three components: Microtubules, Microfilaments, Intermediate Filaments.
• Microtubules are made of tubulin.
• Microfilaments are made of actin.
• Main functions: support, shape maintenance, motility, and intracellular transport.

One-Line NEET Revision

Cytoskeleton is a proteinaceous network of microtubules, microfilaments, and intermediate filaments that provides support, maintains cell shape, and helps in cell movement. 

CYTOSKELETON

│

├── Definition

│   ├── Network of protein fibres

│   ├── Present in cytoplasm

│   └── Internal framework of cell

│

├── Components

│   │

│   ├── Microtubules

│   │   ├── Hollow tubes

│   │   ├── Made of tubulin

│   │   └── Help in cell division & transport

│   │

│   ├── Microfilaments

│   │   ├── Thin fibres

│   │   ├── Made of actin

│   │   └── Help in cell movement

│   │

│   └── Intermediate Filaments

│       ├── Medium-sized fibres

│       ├── Provide strength

│       └── Maintain stability

│

├── Functions

│   │

│   ├── Mechanical Support

│   ├── Maintains Cell Shape

│   ├── Cell Motility (Movement)

│   ├── Movement of Organelles

│   └── Cell Division

│

└── NEET Revision

    ├── Proteinaceous network

    ├── 3 Components

    │   ├── Microtubules

    │   ├── Microfilaments

    │   └── Intermediate Filaments

    ├── Tubulin → Microtubules

    ├── Actin → Microfilaments

    └── Support + Shape + Movement  

Internal Links

Cell Structure and Function (NEET Notes)

Plasma Membrane: Structure and Transport

Cell Organelles: Mitochondria, Golgi Body, ER

Cell Division: Mitosis and Meiosis Notes

Prokaryotic vs Eukaryotic Cell Differences

Cytoplasm and Cytosol Explained Simply

Cytoskeleton Question Bank (CBSE Class 11 Biology)

A. Multiple Choice Questions (MCQs)

1. Cytoskeleton is composed of:

• a) Ribosomes, lysosomes, vacuoles
• b) Microtubules, microfilaments, intermediate filaments
• c) Nucleus, ER, Golgi body
• d) DNA, RNA, proteins

Answer: b) Microtubules, microfilaments, intermediate filaments

2. Microtubules are made up of:

• a) Actin
• b) Tubulin
• c) Keratin
• d) Myosin

Answer: b) Tubulin

3. Microfilaments are primarily composed of:

• a) Actin
• b) Tubulin
• c) Keratin
• d) Cellulose

Answer: a) Actin

4. Which structure provides mechanical support to the cell?

• a) Cytoskeleton
• b) Ribosome
• c) Lysosome
• d) Vacuole

Answer: a) Cytoskeleton

5. Intermediate filaments mainly help in:

• a) Protein synthesis
• b) Cell respiration
• c) Structural stability
• d) Digestion

Answer: c) Structural stability

B. Very Short Answer Questions

1. What is cytoskeleton?

Answer: Cytoskeleton is a network of proteinaceous filaments present in the cytoplasm that provides support and shape to the cell.

2. Name the three components of cytoskeleton.

Answer: Microtubules, Microfilaments and Intermediate filaments.

3. Which protein forms microtubules?

Answer: Tubulin.

4. Which protein forms microfilaments?

Answer: Actin.

5. Where is the cytoskeleton located?

Answer: In the cytoplasm of the cell.

C. Short Answer Questions

1. Mention any three functions of the cytoskeleton.

Answer:

• Provides mechanical support.
• Maintains cell shape.
• Helps in cell movement.

2. Differentiate between microtubules and microfilaments.

Microtubules	Microfilaments
Made of tubulin	Made of actin
Hollow structures	Solid thin fibres
Help in cell division	Help in cell movement

3. Why is cytoskeleton called the framework of the cell?

Answer: It forms an internal supporting network that maintains the shape, organization and movement of the cell.

D. Long Answer Questions

1. Explain the structure and functions of the cytoskeleton.

Answer:
The cytoskeleton is a network of filamentous proteinaceous structures present in the cytoplasm.

Components:

1. Microtubules – made of tubulin.
2. Microfilaments – made of actin.
3. Intermediate filaments – provide strength.

Functions:

• Provides mechanical support.
• Maintains cell shape.
• Helps in cell movement.
• Aids movement of organelles.
• Participates in cell division.

2. Describe the components of the cytoskeleton and their roles.

Answer: Microtubules are hollow tubulin structures involved in transport and cell division. Microfilaments are actin fibres involved in movement and shape changes. Intermediate filaments provide tensile strength and stability. Together they form the cytoskeleton that supports the cell.

E. Assertion and Reason Questions

1. Assertion (A): Cytoskeleton helps maintain cell shape.
Reason (R): Cytoskeleton forms an internal framework in the cytoplasm.

Answer: Both A and R are true, and R is the correct explanation of A.

2. Assertion (A): Microtubules are made of actin.
Reason (R): Actin forms microfilaments.

Answer: A is false, but R is true.

3. Assertion (A): Intermediate filaments provide structural support.
Reason (R): They increase the strength of the cell.

Answer: Both A and R are true, and R is the correct explanation.

F. Fill in the Blanks

1. Cytoskeleton is made up of ________, microfilaments and intermediate filaments.

Answer: Microtubules

2. Microtubules are made of ________ protein.

Answer: Tubulin

3. Microfilaments are composed of ________.

Answer: Actin

4. Cytoskeleton helps in maintaining the ________ of the cell.

Answer: Shape

5. Intermediate filaments provide ________ support.

Answer: Mechanical

G. Match the Columns

Column I	Column II
A. Microtubules	3. Tubulin
B. Microfilaments	1. Actin
C. Intermediate Filaments	2. Structural Stability

H. Case Study Questions

A scientist observed that a cell had lost its normal shape and was unable to move properly. Further investigation revealed damage to the protein fibres present in the cytoplasm.

1. Which cell structure was damaged?

Answer: Cytoskeleton

2. Name the three components of this structure.

Answer: Microtubules, Microfilaments and Intermediate Filaments

3. Which component is made of actin?

Answer: Microfilaments

4. State one function of the damaged structure.

Answer: Maintenance of cell shape

5. Which component provides maximum structural stability?

Answer: Intermediate Filaments