Name: cytoplasm and the cell’s internal framework
Uploaded: 2026-06-01T06:28:36.752Z
Duration: 1 min 16 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.3

Cytoplasm

- [Narratore] Nelle cellule eucariotiche,

il citoplasma è l'area

tra la membrana plasmatica
e l'involucro nucleare.

Poiché le cellule procariotiche
non hanno un nucleo,

il citoplasma si riferisce
a tutto ciò che si trova

all'interno della membrana plasmatica.

In entrambi i tipi di cellule,
lo spazio citoplasmatico

è riempito da una matrice
gelatinosa chiamata citosol,

una soluzione acquosa che
contiene molti ioni solubili,

piccole molecole e macromolecole.

Esclusivamente nelle cellule eucariotiche,

il citoplasma contiene molti
organelli dotati di membrana

sospesi nel citosol,

nonché il citoscheletro,

una rete di fibre che conferisce
alle cellule la loro forma

e facilità la motilità e
il trasporto cellulare.

Ma il citoplasma è anche
il luogo in cui avvengono

molte funzioni non legate agli organelli,

come la sintesi delle
proteine dai ribosomi liberi.

Inoltre, la natura acquosa del citoplasma

facilita il ripiegamento delle proteine

respingendo i gruppi
amminoacidici, idrofobici,

verso il nucleo proteico.

Thomas, Clément e Christopher J. Staiger. "Un'interazione dinamica tra le membrane e il citoscheletro fondamentale per lo sviluppo e la segnalazione cellulare." Frontiers in Plant Science 5 (2014): 335. [<a href="https://doi.org/10.3389/fpls.2014.00335">Fonte</a>]
Sweeney, Patrick, Hyunsun Park, Marc Baumann, John Dunlop, Judith Frydman, Ron Kopito, Alexander McCampbell, et al. 2017. "Ripiegamento errato delle proteine nelle malattie neurodegenerative: implicazioni e strategie". Neurodegenerazione traslazionale 6 (1): 6. [<a href="https://doi.org/10.1186/s40035-017-0077-5">Sorgente</a>]

citoplasma

Il citoplasma è costituito da organelli, una soluzione acquosa chiamata citosol e una struttura di scaffold (impalcatura/assemblaggio) proteici chiamati citoscheletro. Il citosol è un ricco brodo di ioni, piccole molecole organiche come il glucosio e macromolecole come le proteine. Diversi processi cellulari, compresa la sintesi proteica si verificano nel citoplasma.

La composizione del citosol favorisce il ripiegamento delle proteine in modo tale che le catene laterali degli amminoacidi idrofobici siano orientate lontano dalla soluzione acquosa e verso il nucleo proteico. Tuttavia, fattori di stress cellulari come l'invecchiamento e cambiamenti di pH, temperatura, o osmolarità causano proteina misfolding. Le proteine piegate male possono aggregarsi per formare depositi insolubili nel citoplasma. Gli aggregati di proteine insolubili sono implicati in disturbi neurodegenerativi come il morbo di Alzheimer, il morbo di Parkinson e la sclerosi laterale amiotrofica.

<h4>Composizione e funzione del citoscheletro</h4>

Il citoscheletro eucariotico è costituito da tre tipi di proteine filamentose: microtubuli, microfilamenti e filamenti intermedi.

I microtubuli, il più grande tipo di filamento, sono costituiti dalla tubulina proteica. I microtubuli sono strutture dinamiche che possono crescere o ridursi aggiungendo o rimuovendo molecole di tubulina dalle estremità dei loro fili. Forniscono stabilità strutturale e forniscono tracce per il trasporto di proteine e vesciche all'interno della cellula. Inoltre, i microtubuli svolgono un ruolo cruciale nella divisione cellulare fornendo un quadro che guida i cromosomi alle estremità opposte della cellula.

I microfilamenti sono il più piccolo tipo di filamenti citoscheletrici e sono costituiti da una proteina chiamata actina. I filamenti di Actin possono assemblarsi e smontare rapidamente. Pertanto, consentono il movimento in organismi unicellulari come l'ameba o la migrazione dei globuli bianchi ai siti di infezione. Nelle cellule muscolari scheletriche, filamenti di actina scorrono lungo filamenti di miosina per mediare la contrazione muscolare.

I filamenti intermedi non sono dinamici come microtubuli o filamenti di actina. Forniscono supporto strutturale e sono costituiti da diversi tipi di proteine in base al tipo di cellula specifico. Per esempio, filamenti intermedi nei capelli e nelle unghie contengono cheratina mentre le cellule muscolari contengono desmine.

Citoplasma

Il citoplasma è costituito da organelli e da una struttura di scaffold proteici chiamati citoscheletro sospeso in una soluzione acquosa, il citosol. Le...

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Education

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Biologia

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Cell Structure and Function

Struttura e funzione della cellula

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 face the cytosol. Cell stress, such as aging or changes in pH, temperature, or osmolarity, can cause proteins to misfold. These misfolded proteins may clump together into insoluble aggregates in the cytoplasm. Such aggregates are linked to neurodegenerative disorders, including Alzheimer’s disease and Parkinson’s disease.

The eukaryotic cytoskeleton has three main kinds of filamentous proteins: microtubules, microfilaments, and intermediate filaments. Microtubules are the largest filaments and are made of tubulin. They can grow or shrink by adding or removing tubulin at their ends. Microtubules help support cell shape, act as tracks for moving proteins, vesicles, and some organelles, and help guide chromosomes to opposite ends of the cell during division.

Microfilaments, also called actin filaments, are smaller and are built from actin. They can assemble and disassemble quickly. This fast change helps amoebas move and helps white blood cells migrate to infection sites. In skeletal muscle cells, actin filaments slide along myosin filaments to drive muscle contraction.

Intermediate filaments are less dynamic than microtubules and actin filaments, but they still give the cell strength and support. Their protein makeup depends on the cell type. For example, intermediate filaments in hair and nails contain keratin. In muscle cells, they are made of desmins.

Cytoplasm and the Cell’s Internal Framework

cytoplasm-and-the-cells-internal-framework

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...

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...

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.

cytoplasm

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...

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

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...

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 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...

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 cytoplasm, cytosol, and the cytoskeleton support cell structure, protein folding, transport, and movement in high school biology.

Cytoplasm and the Cell’s Internal Framework | JoVE K12

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The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

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As they leave the Endoplasmic Reticulum (ER), properly folded and assembled proteins are selectively packaged into vesicles. These vesicles are ...

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Cytoplasm and the Cell’s Internal Framework

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