What Intracellular Structure Helps Animal Cells to Maintain Their Shape?

If you were to remove all the organelles from a prison cell, would the plasma membrane and the cytoplasm be the only components left? No. Inside 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, permit cytoplasm and vesicles to motility within the jail 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 (Figure). Here, we volition examine each.

Microfilaments thicken the cortex around the inner edge of a cell; like safety 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 concord organelles in place.

Microfilaments

Of the three types of poly peptide fibers in the cytoskeleton, microfilaments are the narrowest. They part in cellular movement, have a diameter of near 7 nm, and are made of two intertwined strands of a globular protein chosen actin (Figure). For this reason, microfilaments are likewise known as actin filaments.

Microfilaments are made of two intertwined strands of actin.

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

Microfilaments likewise provide some rigidity and shape to the cell. They tin depolymerize (disassemble) and reform quickly, thus enabling a cell to modify its shape and move. White blood cells (your body's infection-fighting cells) brand good use of this power. They can move to the site of an infection and phagocytize the pathogen.

Link to Learning

To come across an example of a white blood cell in activeness, scout a short fourth dimension-lapse video of the cell capturing two bacteria. It engulfs one and and then moves on to the other.

Intermediate Filaments

Intermediate filaments are made of several strands of gristly proteins that are wound together (Figure). These elements of the cytoskeleton get their name from the fact that their bore, viii to 10 nm, is betwixt those of microfilaments and microtubules.

Intermediate filaments consist of several intertwined strands of gristly proteins.

Intermediate filaments have no part in cell move. Their function is purely structural. They bear tension, thus maintaining the shape of the cell, and ballast the nucleus and other organelles in place. Effigy shows how intermediate filaments create a supportive scaffolding inside the cell.

The intermediate filaments are the most diverse group of cytoskeletal elements. Several types of gristly proteins are found in the intermediate filaments. You are probably most familiar with keratin, the gristly poly peptide that strengthens your hair, nails, and the epidermis of the pare.

Microtubules

As their proper name implies, microtubules are small hollow tubes. The walls of the microtubule are fabricated of polymerized dimers of α-tubulin and β-tubulin, 2 globular proteins (Figure). With a bore of near 25 nm, microtubules are the widest components of the cytoskeleton. They aid the jail cell resist pinch, provide a rails along which vesicles move through the cell, and pull replicated chromosomes to reverse ends of a dividing prison cell. Like microfilaments, microtubules tin deliquesce and reform quickly.

Microtubules are hollow. Their walls consist of xiii polymerized dimers of α-tubulin and β-tubulin (correct prototype). The left image shows the molecular structure of the tube.

Microtubules are also the structural elements of flagella, cilia, and centrioles (the latter are the two perpendicular bodies of the centrosome). In fact, in fauna cells, the centrosome is the microtubule-organizing center. In eukaryotic cells, flagella and cilia are quite different structurally from their counterparts in prokaryotes, every bit discussed below.

Flagella and Cilia

To refresh your retention, flagella (atypical = flagellum) are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell (for example, sperm, Euglena). When nowadays, the prison cell has just ane flagellum or a few flagella. Whencilia (singular = cilium) are present, nevertheless, many of them extend along the entire surface of the plasma membrane. They are short, hair-like structures that are used to move entire cells (such as paramecia) or substances along the outer surface of the cell (for example, the cilia of cells lining the Fallopian tubes that motility the ovum toward the uterus, or cilia lining the cells of the respiratory tract that trap particulate matter and motion it toward your nostrils.)

Despite their differences in length and number, flagella and cilia share a mutual structural arrangement of microtubules chosen a "9 + two assortment." This is an appropriate name because a single flagellum or cilium is fabricated of a ring of nine microtubule doublets, surrounding a unmarried microtubule doublet in the center (Figure).

This manual electron micrograph of ii flagella shows the nine + 2 array of microtubules: nine microtubule doublets environs a unmarried microtubule doublet. (credit: modification of piece of work by Dartmouth Electron Microscope Facility, Dartmouth College; scale-bar data from Matt Russell)

Y'all have now completed a wide survey of the components of prokaryotic and eukaryotic cells. For a summary of cellular components in prokaryotic and eukaryotic cells, see Table.

Components of Prokaryotic and Eukaryotic Cells
Cell Component	Function	Present in Prokaryotes?	Present in Animate being Cells?	Present in Plant Cells?
Plasma membrane	Separates cell from external environment; controls passage of organic molecules, ions, water, oxygen, and wastes into and out of prison cell	Yep	Yes	Yes
Cytoplasm	Provides turgor pressure to institute cells as fluid within the central vacuole; site of many metabolic reactions; medium in which organelles are institute	Yes	Aye	Yes
Nucleolus	Darkened area within the nucleus where ribosomal subunits are synthesized.	No	Yes	Yeah
Nucleus	Cell organelle that houses DNA and directs synthesis of ribosomes and proteins	No	Yes	Yes
Ribosomes	Protein synthesis	Yes	Aye	Yes
Mitochondria	ATP production/cellular respiration	No	Yes	Yeah
Peroxisomes	Oxidizes and thus breaks downward fat acids and amino acids, and detoxifies poisons	No	Yes	Yes
Vesicles and vacuoles	Storage and ship; digestive function in constitute cells	No	Yep	Yes
Centrosome	Unspecified function in cell division in animate being cells; source of microtubules in animal cells	No	Yes	No
Lysosomes	Digestion of macromolecules; recycling of worn-out organelles	No	Yes	No
Prison cell wall	Protection, structural support and maintenance of jail cell shape	Yes, primarily peptidoglycan	No	Yep, primarily cellulose
Chloroplasts	Photosynthesis	No	No	Yes
Endoplasmic reticulum	Modifies proteins and synthesizes lipids	No	Aye	Yes
Golgi appliance	Modifies, sorts, tags, packages, and distributes lipids and proteins	No	Yes	Aye
Cytoskeleton	Maintains jail cell's shape, secures organelles in specific positions, allows cytoplasm and vesicles to move within cell, and enables unicellular organisms to motion independently	Yep	Yes	Yes
Flagella	Cellular locomotion	Some	Some	No, except for some found sperm cells.
Cilia	Cellular locomotion, motion of particles along extracellular surface of plasma membrane, and filtration	Some	Some	No

Department Summary

The cytoskeleton has three different types of protein elements. From narrowest to widest, they are the microfilaments (actin filaments), intermediate filaments, and microtubules. Microfilaments are often associated with myosin. They provide rigidity and shape to the cell and facilitate cellular movements. Intermediate filaments bear tension and anchor the nucleus and other organelles in place. Microtubules help the cell resist pinch, serve every bit tracks for motor proteins that motility vesicles through the prison cell, and pull replicated chromosomes to opposite ends of a dividing cell. They are also the structural chemical element of centrioles, flagella, and cilia.

Review Questions

Which of the post-obit accept the ability to disassemble and reform rapidly?

1. microfilaments and intermediate filaments
2. microfilaments and microtubules
3. intermediate filaments and microtubules
4. only intermediate filaments

Which of the post-obit exercise not play a role in intracellular movement?

1. microfilaments and intermediate filaments
2. microfilaments and microtubules
3. intermediate filaments and microtubules
4. only intermediate filaments

Free Response

What are the similarities and differences between the structures of centrioles and flagella?

How do cilia and flagella differ?

Glossary

cilium

(plural = cilia) short, hair-similar structure that extends from the plasma membrane in big numbers and is used to move an entire prison cell or move substances along the outer surface of the cell

cytoskeleton

network of protein fibers that collectively maintain the shape of the cell, secure some organelles in specific positions, let cytoplasm and vesicles to move inside the jail cell, and enable unicellular organisms to move independently

flagellum

(plural = flagella) long, hair-like construction that extends from the plasma membrane and is used to move the cell

intermediate filament

cytoskeletal component, composed of several intertwined strands of gristly poly peptide, that bears tension, supports cell-prison cell junctions, and anchors cells to extracellular structures

microfilament

narrowest element of the cytoskeleton system; it provides rigidity and shape to the jail cell and enables cellular movements

microtubule

widest element of the cytoskeleton system; it helps the jail cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing jail cell, and is the structural element of centrioles, flagella, and cilia

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Source: https://courses.lumenlearning.com/sanjacinto-biology1/chapter/the-cytoskeleton/

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