Name: suspensions, sedimentation, and colloids
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 17 s
Channel: JoVE

Kolloide und Suspensionen sind heterogene Gemische aus zwei oder mehr physikalisch miteinander vermischten Komponenten.
In einem Kolloid reicht die Größe der gelösten Partikel von 1 bis 1000 Nanometern, klein genug, dass sie einzeln unsichtbar sind. Diese gelösten Partikel können jedoch Licht streuen, wodurch Kolloide durchscheinend oder undurchsichtig erscheinen. Sie verbleiben auf unbestimmte Zeit in der Lösung und setzen sich nicht ab.
Cytosol, das halbflüssige Material im Inneren lebender Zellen, ist aufgrund der zahlreichen Proteine und Metaboliten, die darin dispergiert sind, ein Kolloid.
Im Gegensatz dazu enthalten Suspensionen große Partikel, in der Regel über 10000 Nanometer, die oft mit bloßem Auge sichtbar sind.
Ungestört setzen sich diese Partikel als Sedimente ab.
Blut ist ein Beispiel für eine Suspension. Wenn frisch entnommenes Blut einige Zeit ungestört bleibt, setzen sich die roten Blutkörperchen am Boden des Behälters ab. Der obere flüssige Teil, das sogenannte Blutplasma, ist eine Lösung aus kleinen gelösten Stoffen sowie einem Kolloid, das größere Plasmaproteine enthält.

kolloide und suspensionen

Kinder beim Spielen machen oft Suspensionen, wie zum Beispiel eine Mischung aus Schlamm und Wasser, Mehl und Wasser oder eine Suspension fester Pigmente in Wasser, die als Temperafarbe bekannt ist. Diese Suspensionen sind heterogene Mischungen, die aus relativ großen Partikeln bestehen, die mit bloßem Auge sichtbar sind oder mit einer Lupe betrachtet werden können. Sie sind trübe und die suspendierten Partikel setzen sich nach dem Mischen ab. Die suspendierten Partikel einer Suspension setzen sich nach einer bestimmten Zeit des Mischens ab. Die Trennung der Partikel von einer Suspension wird Sedimentation genannt. Ein Bluttest zur Bestimmung der Sedimentationsrate misst, wie schnell sich rote Blutkörperchen in einem Reagenzglas aus dem wässrigen Teil des Blutes (bekannt als Plasma) in einer festgelegten Zeit absetzen. Eine schnelle Sedimentation von Blutzellen tritt normalerweise in einem gesunden Körper nicht auf. Es gibt jedoch Krankheiten, die dazu führen können, dass Blutzellen zusammenklumpen, und diese schweren Zellklumpen setzen sich schneller am Boden des Reagenzglases ab als normale Blutzellen. Eine andere Klasse von Mischungen, die als Kolloide (oder kolloidale Dispersionen) bezeichnet werden, weisen Eigenschaften auf, die zwischen denen von Suspensionen und Lösungen liegen. Die Partikel in einem Kolloid sind größer als die meisten einfachen Moleküle; jedoch sind kolloidale Partikel klein genug, dass sie im Ruhezustand nicht absinken. Die Partikel in einem Kolloid sind groß genug, um Licht zu streuen; ein Phänomen, das als Tyndall-Effekt bezeichnet wird; deshalb erscheinen kolloidale Mischungen trüb oder undurchsichtig, wie Suchscheinwerferstrahlen. Wolken sind auch kolloidale Mischungen. Sie bestehen aus Wassertröpfchen, die viel größer sind als Moleküle, aber klein genug, um nicht abzusinken. Einige Kolloide haben die Eigenschaft, Sol-Gel-Umwandlungen durchzumachen, bei denen sie reversibel von einem flüssigen in einen festen (Gel-)Zustand übergehen können. Zum Beispiel wird Gelatine bei Kälte fest und bildet ein Gel, das bei Erwärmung wieder verflüssigt werden kann. Die Sol-Gel-Eigenschaft des Zytoplasmas, der Flüssigkeit lebender Zellen, ist für viele zelluläre Aktivitäten, wie Zellteilung oder Veränderung der Zellform, essentiell. Die partikuläre Komponente einer kolloidalen Lösung, die in relativ geringer Menge vorhanden ist, wird als dispergierte Phase bezeichnet. Die Substanz oder Lösung, in der die Partikel verteilt sind, wird als Dispersionsmedium bezeichnet. Dieser Text ist adaptiert von <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-4-inorganic-compounds-essential-to-human-functioning">Openstax, Anatomy and Physiology 2e, Section 2.4: Inorganic Compounds Essential to Human Functioning</a> and <a href="https://openstax.org/books/chemistry-2e/pages/11-5-colloids">Openstax, Chemistry 2e, Section 11.5: Colloids</a>.

Kolloide und Suspensionen

Kinder stellen beim Spielen oft Suspensionen her, wie z. B. Mischungen aus Schlamm und Wasser, Mehl und Wasser oder eine Suspension von festen Pigmenten in Wasser, die als Tempera bekannt sind ...

Education

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Anatomy and Physiology

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Unit 1

Einheit 1

Fundamentals of Chemistry

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KEY TERMS AND CONCEPTS

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Colloids and Suspensions

suspensions, sedimentation, and colloids

Suspensions and colloids are two common kinds of mixtures seen in everyday life. Mud and water, flour and water, and tempera paint are suspensions. These mixtures are heterogeneous, which means their particles are not spread out evenly. The particles are relatively large and can be seen with the naked eye or a magnifying glass.

Suspension particles make mixtures cloudy, and they settle out after mixing. The settling of particles in a suspension is called sedimentation. A blood test can measure the rate of sedimentation by showing how fast red blood cells settle out of plasma, the watery part of blood, in a test tube over time. Rapid sedimentation is not usual in a healthy body, but some diseases can cause blood cells to clump together and sink faster than normal cells.

Colloids, also called colloidal dispersions, sit between suspensions and solutions. Their particles are larger than most simple molecules, but they are small enough that they do not settle out when left standing. Colloidal particles are still large enough to scatter light. This is known as the Tyndall effect, and it makes colloids look cloudy or opaque, like a beam from a searchlight.

Clouds are another example of a colloid. They contain water droplets that are bigger than molecules, but still small enough to stay suspended in the air. Some colloids can also change from a fluid sol to a solid gel and back again. Gelatin is one example. It forms a gel when chilled and can become liquid again when heated. The sol-gel behavior of cytosol, the fluid inside living cells, is important for cell division and for changes in cell shape.

In a colloid, the dispersed phase is the particulate part present in smaller amount. The dispersion medium is the substance that carries the particles throughout the mixture. These terms help describe how colloids are organized and why they behave differently from suspensions and solutions.

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Learn how suspensions settle, how sedimentation works, and why colloids stay cloudy without settling. Explore real examples like blood, clouds, and gelatin.

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Suspensions, Sedimentation, and Colloids

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