(a) Muchas proteinas que permanecen distribuidas...

Name: Problem 66, Chapter 13: Química. La ciencia central
Uploaded: 2021-06-08T02:46:49-08:00
Duration: 7 min 12 s
Channel: Shubham Kumar
Description: (a) Muchas proteinas que permanecen distribuidas homogéneamente en un medio acuoso tienen masas moleculares del orden de 30,000 uma o más. ¿En qué sentido es apropiado considerar tales suspensiones como coloides en vez de disoluciones? Explique. (b) ¿Qué nombre general se da a una dispersión coloidal de un líquido en otro? ¿Qué es un agente emulsionante?

(a) Muchas proteinas que permanecen distribuidas homogéneamente en un medio acuoso tienen masas moleculares del orden de 30,000 uma o más. ¿En qué sentido es apropiado considerar tales suspensiones como coloides en vez de disoluciones? Explique. (b) ¿Qué nombre general se da a una dispersión coloidal de un líquido en otro? ¿Qué es un agente emulsionante?

Key Concepts

Emulsions

An emulsion is a type of colloidal dispersion where droplets of one liquid are dispersed in another immiscible liquid. This system is inherently unstable due to a high interfacial energy between the two liquids unless stabilized by additional agents. Emulsions are common in both natural and industrial processes, where controlling the size and distribution of the droplets is crucial to the final characteristics of the mixture.

Colloids

A colloid is a heterogeneous system in which particles of one phase are dispersed in another phase, but with particle sizes larger than those in true solutions. Unlike dissolved molecular species that are uniformly distributed at the molecular level, colloidal particles are large enough to scatter light (the Tyndall effect) yet remain small enough to be stable against sedimentation. This distinction is significant in systems where the particle dimensions determine the physical properties of the dispersion.

Particle Size and Molecular Scale

Many biological macromolecules, such as proteins, have high molecular masses (on the order of tens of thousands of unified atomic mass units), placing them at the boundary between large molecules and small particles. Despite being molecular in nature, when dispersed in water, they behave as colloidal particles because their size is sufficiently greater than that of typical smaller solvent molecules. This results in a dispersion that maintains colloidal characteristics rather than being a true solution.

Emulsion Stabilizers (Emulsifying Agents)

An emulsifying agent is a substance that helps in the formation and stabilization of emulsions by reducing the surface tension between the two immiscible liquids. These agents typically have both hydrophilic and hydrophobic parts, allowing them to reside at the interface between the liquid droplets and the continuous phase, thereby preventing the droplets from coalescing and promoting a stable dispersion.

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