Name: cytoplasm and the cell’s internal support
Uploaded: 2023-04-30T10:29:33.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

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From Molecules to Organisms- Structures and Processes

LS.Bio.1.5

Cytoplasm

Nelle cellule eucariotiche, il citoplasma è l'area tra la membrana plasmatica e l'involucro nucleare.
Poiché le cellule procariotiche sono prive di nucleo, il citoplasma si riferisce a tutto ciò che è racchiuso all'interno della membrana plasmatica.
In entrambi i tipi di cellule, lo spazio citoplasmatico è riempito da una matrice gelatinosa chiamata citosol.
Il citosol è una soluzione acquosa che contiene molti ioni solubili, piccole molecole e macromolecole.
Il citoplasma delle cellule eucariotiche comprende anche numerosi organelli legati alla membrana che svolgono funzioni cellulari specializzate, come i mitocondri, il reticolo endoplasmatico e l'apparato di Golgi.
Una struttura di fibre proteiche presenti nel citoplasma, il citoscheletro, conferisce alla cellula la sua forma e struttura. Aiuta anche nel trasporto intracellulare e nella motilità cellulare.
Inoltre, molte funzioni cellulari non organelli, come la sintesi proteica, si svolgono anche nel citoplasma. La natura acquosa del citoplasma facilita il ripiegamento delle proteine respingendo i gruppi laterali degli aminoacidi idrofobici nel nucleo proteico.
Alcune cellule immagazzinano anche prodotti metabolici insolubili come il glicogeno nel loro citoplasma sotto forma di inclusioni.

citoplasma

Il citoplasma è costituito da organelli e da una struttura di impalcature proteiche chiamata citoscheletro sospesa in una soluzione acquosa, il citosol. Il citosol è un brodo ricco di acqua, ioni, sali e varie molecole organiche.

Ripiegamento e misfolding delle proteine

Il citoplasma è la sede di numerosi processi cellulari, tra cui la sintesi e il ripiegamento delle proteine. La natura acquosa del citosol favorisce il ripiegamento delle proteine in modo tale che le catene laterali degli amminoacidi idrofobici siano sepolte nel nucleo proteico mentre gli amminoacidi idrofili siano rivolti verso il citosol. Tuttavia, gli stress cellulari come l’invecchiamento e i cambiamenti di pH, temperatura o osmolarità possono causare un errato ripiegamento delle proteine. Le proteine mal ripiegate possono accumularsi nel citoplasma per formare aggregati proteici insolubili. Tali aggregati sono implicati nei disturbi neurodegenerativi, come il morbo di Alzheimer e il morbo di Parkinson.

Composizione e funzione del citoscheletro

Il citoscheletro eucariotico è costituito da tre tipi di proteine filamentose: microtubuli, microfilamenti e filamenti intermedi.

I microtubuli, il tipo più grande di filamenti, sono costituiti dalla proteina tubulina. Sono strutture dinamiche che possono crescere o ridursi aggiungendo o rimuovendo molecole di tubulina dalle estremità dei loro filamenti. Forniscono stabilità strutturale alla cellula e fungono da binari per il trasporto di proteine, vescicole e alcuni organelli all'interno della cellula. Inoltre, i microtubuli svolgono un ruolo cruciale nella divisione cellulare fornendo una struttura che guida i cromosomi alle estremità opposte della cellula.

I microfilamenti, o filamenti di actina, sono filamenti citoscheletrici più piccoli costituiti da una proteina chiamata actina. Le proteine dell'actina possono assemblarsi e disassemblarsi rapidamente per formare filamenti. Pertanto, consentono la motilità negli organismi unicellulari come l'ameba o la migrazione dei globuli bianchi verso i siti di infezione. Nelle cellule muscolari scheletriche, i filamenti di actina scivolano lungo i filamenti di miosina per mediare la contrazione muscolare.

I filamenti intermedi non sono dinamici come i microtubuli o i filamenti di actina. Tuttavia, come gli altri due tipi di filamenti, forniscono anche un supporto strutturale alla cellula. I filamenti intermedi sono composti da diversi tipi di proteine in base al tipo cellulare specifico. Ad esempio, i filamenti intermedi nei capelli e nelle unghie contengono cheratina, mentre nelle cellule muscolari questi filamenti sono costituiti da desmina.

Citoplasma

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

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Cells, Genomes, and Evolution

Cellule, genomi ed evoluzione

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

cytoplasm and the cell’s internal support

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. This fluid helps keep the cell organized and supports many cellular activities.

The cytoplasm is also where protein synthesis and protein folding take place. The watery cytosol helps proteins fold correctly. In a folded protein, hydrophobic amino acid side chains tend to stay buried in the core, while hydrophilic amino acids face the cytosol.

Cell stress can disrupt this process. Changes in pH, temperature, osmolarity, or aging can cause proteins to misfold. These misfolded proteins may collect in the cytoplasm and form insoluble aggregates. Such aggregates are linked to neurodegenerative disorders like Alzheimer’s and Parkinson’s disease.

The cytoskeleton is the protein framework inside the cytoplasm. It includes three filament types: microtubules, microfilaments, and intermediate filaments. Microtubules are the largest and are built from tubulin. They can grow or shrink by adding or removing tubulin at their ends. They help give the cell structural stability and serve as tracks for moving proteins, vesicles, and some organelles. They also help guide chromosomes to opposite ends of the cell during cell division.

Microfilaments, also called actin filaments, are smaller and are made of actin. They can assemble and disassemble quickly. This rapid change helps amoeba 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 or actin filaments, but they still provide support. They are made of different proteins depending on the cell type. In hair and nails, intermediate filaments contain keratin. In muscle cells, they are made of desmins.

Cytoplasm and the Cell’s Internal Support

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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. This fluid helps keep the cell organized and supports many cellular activities. The cytoplasm is also where protein synthesis and protein folding take place. The watery cytosol helps proteins fold correctly. In a folded protein, hydrophobic amino acid side chains tend to stay buried in the core, while...

the nucleus

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the dna helix

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key terms and concepts

Learn how the cytoplasm, cytosol, and cytoskeleton support cell structure, protein folding, transport, cell division, movement, and muscle contraction.

Cytoplasm and the Cell’s Internal Support | JoVE K12

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Louisiana Student Standards for Science

High School

Life Sciences

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Cytoplasm and the Cell’s Internal Support

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