<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Describe the cytoskeleton
  • Compare the roles of microfilaments, intermediate filaments, and microtubules
  • Compare and contrast cilia and flagella
  • Summarize the differences among the components of prokaryotic cells, animal cells, and plant cells

If you were to remove all the organelles from a cell, would the plasma membrane and the cytoplasm be the only components left? No. Within the cytoplasm, there would still be ions and organic molecules, plus a network of protein fibers that help maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable cells within multicellular organisms to move. Collectively, this network of protein fibers is known as the cytoskeleton    . There are three types of fibers within the cytoskeleton: microfilaments, intermediate filaments, and microtubules ( [link] ). Here, we will examine each.

Microfilaments line the inside of the plasma membrane, whereas microfilaments radiate out from the center of the cell. Intermediate filaments form a network throughout the cell that holds organelles in place.
Microfilaments thicken the cortex around the inner edge of a cell; like rubber bands, they resist tension. Microtubules are found in the interior of the cell where they maintain cell shape by resisting compressive forces. Intermediate filaments are found throughout the cell and hold organelles in place.

Microfilaments

Of the three types of protein fibers in the cytoskeleton, microfilaments are the narrowest. They function in cellular movement, have a diameter of about 7 nm, and are made of two intertwined strands of a globular protein called actin ( [link] ). For this reason, microfilaments are also known as actin filaments.

This illustration shows two actin filaments wound together. Each actin filament is composed of many actin subunits connected together to form a chain.
Microfilaments are made of two intertwined strands of actin.

Actin is powered by ATP to assemble its filamentous form, which serves as a track for the movement of a motor protein called myosin. This enables actin to engage in cellular events requiring motion, such as cell division in animal cells and cytoplasmic streaming, which is the circular movement of the cell cytoplasm in plant cells. Actin and myosin are plentiful in muscle cells. When your actin and myosin filaments slide past each other, your muscles contract.

Microfilaments also provide some rigidity and shape to the cell. They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move. White blood cells (your body’s infection-fighting cells) make good use of this ability. They can move to the site of an infection and phagocytize the pathogen.

To see an example of a white blood cell in action, click here and watch a short time-lapse video of the cell capturing two bacteria. It engulfs one and then moves on to the other.

Intermediate filaments

Intermediate filaments are made of several strands of fibrous proteins that are wound together ( [link] ). These elements of the cytoskeleton get their name from the fact that their diameter, 8 to 10 nm, is between those of microfilaments and microtubules.

This illustration shows 10 intermediate filament fibers bundled together.
Intermediate filaments consist of several intertwined strands of fibrous proteins.

Intermediate filaments have no role in cell movement. Their function is purely structural. They bear tension, thus maintaining the shape of the cell, and anchor the nucleus and other organelles in place. [link] shows how intermediate filaments create a supportive scaffolding inside the cell.

Questions & Answers

what is the work of phloem tissue
Rose Reply
What is osmoregulation?
Jacklin
osmoregulation is the maintenance of internal body through the aid of water
favour
mention four characteristics of enzymes
Leah
A skeleton is any film structure that gives mechanical support to the body and provides protection to the softer parts of the body.
Patrick Reply
nice
Kabir
A skeleton is a frame or bony part of a body that aid in the movement of different parts of the body.
hamidat
What is a skeleton?
Chipo Reply
is a bone without meat
Stanley
is a frame work of d body that provide support nd rigidity 4 d body
tunz
what is an electron microscope?
Chr Reply
what is biochemist
Lenard Reply
biochemistry:-is the study of chemical reaction with living organisms
Kabir
HOW MANY DNA STRANDS DOES CORONA VIRUS HAVE?
Baramox
what are the scientific method
Precious Reply
describe the functioning of the Golgi body in animal cells
Naiga Reply
what features does red blood have that allows it to effectively move through the blood and transport oxygen? list at least four features and explain how they help RBC's carry out their functions.
Alice Reply
has nucleus, haemoglobin
favour
what is biology
kenneth Reply
it's the study of living organisms and their interactions with one another and the environment
Precious
Biology is the study of life.
hamidat
describe the structure of DNA
Mafashion Reply
it a double helical structure negatively charged as a results of a phosphate backbone and the two strands are joined together by hydrogen bonds
Ebenezer
Bring out clearly the process of clothing
Irene Reply
How is the region of unwinding called
Irene
what is hoemositasis
Violet
homeostasis is the regulation of a constant internal environment
hamidat
is an unfavourable conditions cost by capavic bacteria
hashim Reply
no idea
hamidat
no idea
Precious
Describe the following terms used in nutrition, parasitism, saprophytic, symbiosys
Meymo Reply
parasitism involves gaining and losing
hamidat
a saprophyte does not cause harm to it Host.
hamidat
in symbiosis the two organisms are benefiting
hamidat
what is meiosis?
Emmanuel Reply
Meiosis is a two successive cell division with only one duplication of chromosomes
Amos
what are types of white cells
Kennedy Reply
phagocytes and lymphocytes
Luyando
Lymphocytes and phagocytosis
Sylvester
which plant tissue conducts sucrose in solution?
Luyando
granulocytes and agranulocytes
dilip
phloem
dilip
granulocytes and agranulocyte
Irene

Get the best Biology course in your pocket!





Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?

Ask