Lecture 15 - Cytoskeleton | Cell Biology- Botany PDF Download

 Page 1


Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
 
 
 
 
 
 
Lesson: Cytoskeleton 
Lesson Developer: Sandeepa Singh 
College/ Department: Maitreyi College, University of Delhi 
Page 2


Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
 
 
 
 
 
 
Lesson: Cytoskeleton 
Lesson Developer: Sandeepa Singh 
College/ Department: Maitreyi College, University of Delhi 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents 
Chapter: Cytoskeleton  
? Introduction  
? Microfilaments 
? Polymerization of actin filaments 
? Types of actin 
? Organization of actin filaments within the cell and their 
relation with plasma membrane 
? RBCs and the study of cytoskeleton 
? Association of actin with myosin and their role in cell 
movement 
? Myosin and molecular mechanism of muscle contraction 
? Intermediate Filaments 
? Types of proteins that make intermediate filaments  
? Assembly and function of intermediate filaments  
? Microtubules  
? Structure of microtubules 
? Assembly and role of microtubules 
o Microtubules and cargo transport 
o Rearrangement of microtubules at mitosis and 
chromosome movement 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
 
Page 3


Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
 
 
 
 
 
 
Lesson: Cytoskeleton 
Lesson Developer: Sandeepa Singh 
College/ Department: Maitreyi College, University of Delhi 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents 
Chapter: Cytoskeleton  
? Introduction  
? Microfilaments 
? Polymerization of actin filaments 
? Types of actin 
? Organization of actin filaments within the cell and their 
relation with plasma membrane 
? RBCs and the study of cytoskeleton 
? Association of actin with myosin and their role in cell 
movement 
? Myosin and molecular mechanism of muscle contraction 
? Intermediate Filaments 
? Types of proteins that make intermediate filaments  
? Assembly and function of intermediate filaments  
? Microtubules  
? Structure of microtubules 
? Assembly and role of microtubules 
o Microtubules and cargo transport 
o Rearrangement of microtubules at mitosis and 
chromosome movement 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 2 
Introduction 
Cytoskeleton are the proteinaceous structures present in the cytoplasm of the cell which 
provide the skeletal support to the cell and are also responsible for the movements in / of the 
cell. Although it was known earlier that 20-30% of cytosol comprises of proteins, very little 
was understood about their enzymatic activity and structural or functional roles.  Advancement 
in sophisticated investigative techniques like fluorescence microscopy, electron microscopy and 
digital video microscopy led to an insight into the world of eukaryotic cell and it revealed the 
presence of cytoskeleton, which consists of various interconnected protein filaments, forming 
an intricate network spreading throughout the cytosol, from the nucleus to the inner leaflet of 
plasma membrane. 
 
Figure: The eukaryotic cytoskeleton: Actin filaments are shown in red, microtubules in green, 
and the nuclei are in blue. 
Source:https://en.wikipedia.org/wiki/Cytoskeleton 
Cytoskeleton refers to the network of polymers which forms the architectural framework of the 
cell, thus providing the latter enough strength to assume complex shapes, besides helping in 
carrying out diverse cellular processes. Besides providing shape to the cell, cytoskeleton also 
plays a vital role in essential activities of the cells that include: 
? maintenance of cell shape, cell division 
?  cell movement 
?  movement of organelles and vesicles within the cells 
Page 4


Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
 
 
 
 
 
 
Lesson: Cytoskeleton 
Lesson Developer: Sandeepa Singh 
College/ Department: Maitreyi College, University of Delhi 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents 
Chapter: Cytoskeleton  
? Introduction  
? Microfilaments 
? Polymerization of actin filaments 
? Types of actin 
? Organization of actin filaments within the cell and their 
relation with plasma membrane 
? RBCs and the study of cytoskeleton 
? Association of actin with myosin and their role in cell 
movement 
? Myosin and molecular mechanism of muscle contraction 
? Intermediate Filaments 
? Types of proteins that make intermediate filaments  
? Assembly and function of intermediate filaments  
? Microtubules  
? Structure of microtubules 
? Assembly and role of microtubules 
o Microtubules and cargo transport 
o Rearrangement of microtubules at mitosis and 
chromosome movement 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 2 
Introduction 
Cytoskeleton are the proteinaceous structures present in the cytoplasm of the cell which 
provide the skeletal support to the cell and are also responsible for the movements in / of the 
cell. Although it was known earlier that 20-30% of cytosol comprises of proteins, very little 
was understood about their enzymatic activity and structural or functional roles.  Advancement 
in sophisticated investigative techniques like fluorescence microscopy, electron microscopy and 
digital video microscopy led to an insight into the world of eukaryotic cell and it revealed the 
presence of cytoskeleton, which consists of various interconnected protein filaments, forming 
an intricate network spreading throughout the cytosol, from the nucleus to the inner leaflet of 
plasma membrane. 
 
Figure: The eukaryotic cytoskeleton: Actin filaments are shown in red, microtubules in green, 
and the nuclei are in blue. 
Source:https://en.wikipedia.org/wiki/Cytoskeleton 
Cytoskeleton refers to the network of polymers which forms the architectural framework of the 
cell, thus providing the latter enough strength to assume complex shapes, besides helping in 
carrying out diverse cellular processes. Besides providing shape to the cell, cytoskeleton also 
plays a vital role in essential activities of the cells that include: 
? maintenance of cell shape, cell division 
?  cell movement 
?  movement of organelles and vesicles within the cells 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 3 
?  cell-cell interaction and  
? cell signaling. 
Cytoskeleton consists of three major types of filaments namely  
1. Microfilaments 
2. Microtubules and  
3. Intermediate filaments.  
 
Source:http://www.phschool.com/science/biology_place/biocoach/images/cells/Cytoskel.gif 
These remain connected with each other throughout the cytosol. Presence of these elements 
within the cell was demonstrated by electron microscopy and fluorescence microscopy. 
Cytoskeletal filaments can be viewed in live cells with the help of sophisticated techniques like 
live cell fluorescence imaging using fluorescent proteins, such as GFP. The GFP protein is 
obtained from jellyfish Aequorea victoria and is a very stable protein, therefore it is used as a 
cell or tissue specific marker. Fluorescent proteins enable plant cell structure to be visualized 
in live cells and therefore, the location of diiferent proteins can be determined within the cell. 
In this technique, cytoskeletal proteins are made fluorescent and introduced in living cells and 
their role inside the cell is examined.  
In another technique (computer enhanced video microscopy), high resolution images are 
obtained using digital camera attached to microscope and processed by computer to obtain a 
better image. 
Page 5


Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 
 
 
 
 
 
 
 
 
 
 
Lesson: Cytoskeleton 
Lesson Developer: Sandeepa Singh 
College/ Department: Maitreyi College, University of Delhi 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 1 
Table of Contents 
Chapter: Cytoskeleton  
? Introduction  
? Microfilaments 
? Polymerization of actin filaments 
? Types of actin 
? Organization of actin filaments within the cell and their 
relation with plasma membrane 
? RBCs and the study of cytoskeleton 
? Association of actin with myosin and their role in cell 
movement 
? Myosin and molecular mechanism of muscle contraction 
? Intermediate Filaments 
? Types of proteins that make intermediate filaments  
? Assembly and function of intermediate filaments  
? Microtubules  
? Structure of microtubules 
? Assembly and role of microtubules 
o Microtubules and cargo transport 
o Rearrangement of microtubules at mitosis and 
chromosome movement 
? Summary  
? Exercise/ Practice 
? Glossary 
? References/ Bibliography/ Further Reading 
 
 
 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 2 
Introduction 
Cytoskeleton are the proteinaceous structures present in the cytoplasm of the cell which 
provide the skeletal support to the cell and are also responsible for the movements in / of the 
cell. Although it was known earlier that 20-30% of cytosol comprises of proteins, very little 
was understood about their enzymatic activity and structural or functional roles.  Advancement 
in sophisticated investigative techniques like fluorescence microscopy, electron microscopy and 
digital video microscopy led to an insight into the world of eukaryotic cell and it revealed the 
presence of cytoskeleton, which consists of various interconnected protein filaments, forming 
an intricate network spreading throughout the cytosol, from the nucleus to the inner leaflet of 
plasma membrane. 
 
Figure: The eukaryotic cytoskeleton: Actin filaments are shown in red, microtubules in green, 
and the nuclei are in blue. 
Source:https://en.wikipedia.org/wiki/Cytoskeleton 
Cytoskeleton refers to the network of polymers which forms the architectural framework of the 
cell, thus providing the latter enough strength to assume complex shapes, besides helping in 
carrying out diverse cellular processes. Besides providing shape to the cell, cytoskeleton also 
plays a vital role in essential activities of the cells that include: 
? maintenance of cell shape, cell division 
?  cell movement 
?  movement of organelles and vesicles within the cells 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 3 
?  cell-cell interaction and  
? cell signaling. 
Cytoskeleton consists of three major types of filaments namely  
1. Microfilaments 
2. Microtubules and  
3. Intermediate filaments.  
 
Source:http://www.phschool.com/science/biology_place/biocoach/images/cells/Cytoskel.gif 
These remain connected with each other throughout the cytosol. Presence of these elements 
within the cell was demonstrated by electron microscopy and fluorescence microscopy. 
Cytoskeletal filaments can be viewed in live cells with the help of sophisticated techniques like 
live cell fluorescence imaging using fluorescent proteins, such as GFP. The GFP protein is 
obtained from jellyfish Aequorea victoria and is a very stable protein, therefore it is used as a 
cell or tissue specific marker. Fluorescent proteins enable plant cell structure to be visualized 
in live cells and therefore, the location of diiferent proteins can be determined within the cell. 
In this technique, cytoskeletal proteins are made fluorescent and introduced in living cells and 
their role inside the cell is examined.  
In another technique (computer enhanced video microscopy), high resolution images are 
obtained using digital camera attached to microscope and processed by computer to obtain a 
better image. 
Cytoskeleton 
Institute of Lifelong Learning, University of Delhi 4 
Other important technique used at present can be discussed here, such as live cell 
fluorescence imaging, using GFP and FRAP to monitor the dynamics of the cytoskeleton.  
Microfilaments 
They are the smallest among all cytoskeletal filaments and have a diameter of about 7 nm. 
They are the key elements constituting the contractile filaments of muscle cells, where they 
take part in characteristic muscle contractions in association with myosin filaments. Besides 
their role in muscle contraction the microfialments play an important role in movement of the 
cells, in locomotion, cytoplasmic streaming and various other structural functions. 
Microfilaments are responsible for the formation of cleavage furrow that leads to the division of 
cytoplasm during cytokinesis in animal cells.  
Microfilaments are made up of a protein, known as actin, which constitutes the major protein 
portion of cytoskeleton. Actin polymerizes to form long, flexible filaments which become 
organized into sophisticated higher order three dimensional structures. Actin filaments are 
found in great numbers just below the plasma membrane where they are organized into a 
network to impart mechanical strength and support to the cell.  
Actin protein is made up of 375 amino acids and has a molecular weight of 42 kDa. Actin is 
synthesized in the form of a thin and flexible polypeptide. It is a fairly abundant protein found 
in all eukaryotic cells and individual actin monomers are termed as G-actin (globular actin). 
Under optimum physiological conditions, individual actin monomers polymerize into filaments 
(or microfilaments). In this state actin is termed as F-actin (filamentous actin).  
 
Source: http://education-portal.com/cimages/multimages/16/actin_filament.PNG