Name: microtubules in cells and cell movement
Uploaded: 2026-06-01T06:27:55.759Z
Duration: 1 min 35 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.2

Microtubules

In eukaryotic cells, microtubules are the thickest cytoskeletal elements in cells.They are hollow tubes about 25 nanometers wide. They are usually made of 13 protofilaments made from repeating alpha- and beta-tubulin heterodimers.Each microtubule has structural polarity, with a plus end and a minus end. At the plus end, where beta-tubulin is exposed, cells usually add new dimers. The minus end has alpha-tubulin, is usually less dynamic, and is often attached to a microtubule-organizing center that anchors many microtubules.Microtubules can rapidly grow and shrink. This behavior is known as dynamic instability.Microtubule-associated proteins bind along the sides of microtubules and help control their stability and organization.Microtubule polarity supports directional transport, where motor proteins such as kinesin and dynein move along microtubules and carry cargo, such as vesicles, through the cytoplasm.In eukaryotic cells such as epithelial cells and sperm cells, microtubules form the core of cilia and flagella, which have a characteristic 9+2 arrangement. These structures move fluidly across cell surfaces or propel cells through their environment.

microtubules

There are three types of cytoskeletal structures in eukaryotic cells&#x2014;microfilaments, intermediate filaments, and microtubules. With a diameter of about 25 nm, microtubules are the thickest of these fibers. Microtubules carry out a variety of functions that include cell structure and support, transport of organelles, cell motility (movement), and the separation of chromosomes during cell division.Microtubules are hollow tubes whose walls are made up of globular tubulin proteins. Each tubulin molecule is a heterodimer, consisting of a subunit of &#x3B1;-tubulin and a subunit of &#x3B2;-tubulin. The dimers are arranged in linear rows called protofilaments. A microtubule usually consists of 13 protofilaments, arranged side by side, wrapped around the hollow core.Because of this arrangement, microtubules are polar, meaning that they have different ends. The plus end has &#x3B2;-tubulin exposed, and the minus end has &#x3B1;-tubulin exposed. Microtubules can rapidly assemble&#x2014;grow in length through polymerization of tubulin molecules&#x2014;and disassemble. The two ends behave differently in this regard. The plus end is typically the fast-growing end or the end where tubulin is added, and the minus end is the slow-growing end or the end where tubulin dissociates&#x2014;depending on the situation.This process of dynamic instability, where microtubules rapidly grow and shrink, is important for functions such as the remodeling of the cytoskeleton during cell division and the extension of axons from growing neurons.Microtubules also can be stable, often by binding to microtubule-associated proteins, which help the cell to maintain its shape. Other proteins, called motor proteins, can interact with microtubules to transport organelles in a particular direction. For example, many neurotransmitters are packaged into vesicles in the cell body of a neuron and are then transported down the axon along a &#x201C;track&#x201D; of microtubules, delivering the vesicles to where they are needed. Finally, microtubules can also protrude outside of the cell&#x2014;making up the filamentous flagella and cilia that move to push cells (such as sperm) along, or to move fluid across their surfaces, such as in the lungs.

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Education

JoVE Core

Biology

Cellular Processes

Cell Structure and Function

KEY TERMS AND CONCEPTS

microtubules in cells and cell movement

Microtubules are cytoskeletal fibers that help cells keep their shape, move materials, and divide. They are the thickest of the three main cytoskeletal structures in eukaryotic cells, with a diameter of about 25 nm. Along with microfilaments and intermediate filaments, they form the internal support network of the cell.

Microtubules are hollow tubes built from tubulin proteins. Each tubulin molecule is a heterodimer, which means it has two different parts: α-tubulin and β-tubulin. These dimers line up in rows called protofilaments. A typical microtubule has 13 protofilaments arranged side by side around a hollow center.

This structure gives microtubules polarity, meaning the two ends are different. The plus end exposes β-tubulin, while the minus end exposes α-tubulin. Microtubules can also grow and shrink quickly as tubulin molecules add to or leave the tube. The plus end is usually the faster-growing end, and the minus end is often the slower-growing end, although this can depend on the situation.

This fast assembly and disassembly is called dynamic instability. It helps cells remodel their cytoskeleton during cell division. It also supports the growth of axons in developing neurons. Some microtubules are more stable, often because microtubule-associated proteins bind to them and help the cell hold its shape.

Microtubules also serve as tracks for motor proteins. These proteins move organelles and other cargo in a set direction inside the cell. In neurons, many neurotransmitters are packed into vesicles in the cell body and transported down the axon along microtubules to where they are needed.

Microtubules can also extend outside the cell to form cilia and flagella. These filament-like structures help move cells, such as sperm, or move fluid across cell surfaces, such as in the lungs. Because of these roles, microtubules are important for support, transport, movement, and chromosome separation during cell division.

Microtubules in Cells and Cell Movement

what are cells?

Cell Membrane, DNA, and Organelles

Cells are the basic units of life, from a bacterium made of one cell to a human made of trillions. Even though organisms can differ greatly, their cells share key features that support life. A cell has a plasma membrane, which is a lipid bilayer that separates the cytoplasm from the outside environment. It also contains DNA, the genetic material that carries instructions for the cell. In prokaryotic cells, DNA is found in a region called the nucleoid. In eukaryotic cells, DNA is enclosed...

cell size

Why Cell Size Is Limited

Cell size is limited by surface area and diffusion. Cells vary widely in size, both between organisms and within the same organism. Bacterial cells are usually 1 to 10 micrometers wide, and the smallest bacteria can be 0.1 micrometers in diameter. That is about a thousand times smaller than most eukaryotic cells, which are typically 10 to 100 micrometers across. A cell takes in nutrients and water through diffusion across the plasma membrane or through channels in the membrane. The membrane...

prokaryotic cells

Prokaryotic Cell Structures

Prokaryotic cells are small, single-celled organisms found in the domains Archaea and Bacteria. Bacteria include familiar species such as Salmonella and E. coli. Archaea include extremophiles, which are organisms that live in harsh environments like volcanic springs. Prokaryotic cells share several basic features with eukaryotic cells. They are surrounded by a plasma membrane, contain cytoplasm, and have ribosomes that make proteins. Their genetic material is a single, circular DNA molecule.

eukaryotic compartmentalization

Cell Organelles and Microenvironments

Eukaryotic cells use membrane-bound organelles to keep cell processes organized. The nucleus and mitochondria are two key examples. Because biological membranes are selectively permeable, they create controlled spaces inside each organelle. These small microenvironments support specialized jobs and separate them from the surrounding cytosol. Different organelles maintain different internal conditions. In animal cells, lysosomes keep an acidic environment that helps their enzymes digest...

cytoplasm

Cytoplasm and the Cell’s Internal Framework

The cytoplasm is the cell’s internal space that holds organelles and the cytoskeleton. It is suspended in the cytosol, an aqueous fluid made of water, ions, salts, and many organic molecules. Together, these parts create the environment where key cell activities happen. The cytoplasm is also a major site for protein synthesis and folding. The water-based cytosol helps proteins fold correctly. Hydrophobic amino acid side chains tend to hide in the protein core, while hydrophilic amino acids...

the nucleus

Nuclear DNA and Cell Control

The nucleus is the control center of a eukaryotic cell. It is a membrane-bound organelle that contains chromosomal DNA. That DNA helps control gene expression and regulate protein production in the cell. Not all cellular DNA has the same role. The DNA in mitochondria and chloroplasts supports functions that are specific to those organelles. Inside the nucleus, DNA structure also affects how genes are regulated. Nuclear DNA is wrapped around proteins called histones. This forms chromatin, a...

endoplasmic reticulum

ER in Protein and Lipid Transport

The endoplasmic reticulum is a membrane network in eukaryotic cells. It is continuous with the outer membrane of the nucleus. This connection helps link nuclear and cytoplasmic processes and supports efficient movement inside the cell. mRNA can move from the nucleus to ribosomes, which helps protein synthesis happen efficiently. The ER is a major site for making, processing, and distributing biomolecules. The rough endoplasmic reticulum has ribosomes attached to its surface. These ribosomes...

ribosomes

How Ribosomes Build Proteins

Ribosomes build proteins by reading messenger RNA, or mRNA, and linking amino acids in the right order. Both prokaryotic and eukaryotic cells contain ribosomes. Cells that make large amounts of protein, such as secretory cells in the human pancreas, can have millions of them. Ribosomes are made of ribosomal RNA, or rRNA, and proteins. In eukaryotic cells, rRNA is transcribed from genes in the nucleolus, a part of the nucleus that specializes in making ribosomes. There, rRNA combines with...

golgi apparatus

Protein Sorting in the Golgi Apparatus

The Golgi apparatus sorts and modifies proteins after they leave the endoplasmic reticulum (ER). Properly folded and assembled proteins are packaged into vesicles, or small membrane sacs, and moved by microtubule-based motor proteins. These vesicles can fuse into vesicular tubular clusters before reaching the Golgi, which often looks like a ribbon-shaped organelle in eukaryotic cells. Vesicles enter the cis face of the Golgi, the side facing the ER. They pass through a set of pancake-shaped...

peroxisomes

Peroxisomes and Cellular Detoxification

Peroxisomes and mitochondria are two important oxygen-utilizing organelles in eukaryotic cells. Mitochondria carry out cellular respiration, which turns energy from food into ATP. Peroxisomes focus on breaking down substances such as fatty acids and other materials the cell needs to process. A peroxisome is a single membrane-bound organelle. It helps with lipid metabolism and chemical detoxification. Enzymes inside peroxisomes move hydrogen atoms from molecules to oxygen. This reaction...

Microtubules are cytoskeletal fibers that help cells keep their shape, move materials, and divide. They are the thickest of the three main cytoskeletal structures in eukaryotic cells, with a diameter of about 25 nm. Along with microfilaments and intermediate filaments, they form the internal support network of the cell. Microtubules are hollow tubes built from tubulin proteins. Each tubulin molecule is a heterodimer, which means it has two different parts: α-tubulin and β-tubulin. These dimers...

plant cell wall

Plant Cell Walls in Growth and Support

Plant cell walls help plant cells keep their shape, stay protected, and remain supported. As a cell matures, its wall can change based on the cell type. Parenchyma cells in leaves usually have only a thin primary cell wall. These walls are part of how different plant cells take on different jobs. Collenchyma and sclerenchyma cells are found mostly in the outer layers of stems and leaves. Collenchyma cells add strength by partially thickening the primary cell wall. Sclerenchyma cells provide...

plasmodesmata

Plasmodesmata and Plant Cell Communication

Plasmodesmata are the connections that let plant cells communicate directly. These tiny passageways link neighboring cells through the cell wall and help tissues work together in a multicellular plant. Cells in multicellular organisms must communicate to function as a unit. One way they do this is through intercellular junctions, which are contact points between adjacent cells. Fungal, plant, and animal cells all have intercellular junctions, but the types differ. In animal cells, the main...

the extracellular matrix

How ECM Supports Animal Tissues

The extracellular matrix (ECM) supports animal tissues by surrounding cells with structural molecules. It helps maintain tissue organization and gives tissues their specific physical properties. The ECM includes a gel-like ground substance, fibrous components, and many molecules with different jobs. A major part of the ECM is made of glycosaminoglycans, or GAGs. These polysaccharides fill much of the extracellular space and can take up a large volume for their mass. That makes the matrix...

gap junctions

Connexins and Cell-to-Cell Signaling

Gap junctions help animal cells send signals and share small materials with nearby cells. They are made of special proteins that form pores between neighboring cells and connect their cytoplasm. Through these channels, cells can exchange ions and other small molecules. These communication channels are found in many invertebrate and vertebrate species. They support important processes such as cell differentiation and development. They are also linked to human diseases, including disorders of...

tissues

Body Tissues and Their Jobs

Body tissues are groups of cells with similar structure and function. When different tissues work together, they form an organ with a specialized job. Vertebrates have four main tissue types: epithelial, connective, muscle, and nervous tissue. Epithelial tissue is made of thin sheets of cells. It covers the skin and lines internal organs and body cavities. These cells are tightly packed, so they help protect against injury, infection, and water loss. Epithelial tissue may be simple, with one...

key terms and concepts

Learn how microtubules support cell shape, move vesicles, drive cilia and flagella, and help separate chromosomes during cell division.

Microtubules in Cells and Cell Movement | JoVE K12

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biology

SC.912.L.14.3

Microtubules in Cells and Cell Movement

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