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La célula Membranas biológicas

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Forma Tamaño Estructura Componentes

Diversidad Especialización Organización

Entorno

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LO MAS PEQUEÑO…

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¿Pueden existir células más pequeñas? Hay un límite? La restricción de la membrana:

La membrana plasmática tiene 10 uM por lo tanto el diámetro celular debería ser al menos de 30 uM

Espacio/volumen

Hay un mínimo de reacciones enzimáticas que garantizan la vida celular (100 reacciones enzimáticas diferentes). Para ello se necesitan al menos 40 uM!

Masa / Volumen

Presencia de moléculas de reserva pueden incrementar el tamaño mínimo a 50 uM!

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¿Cual es la célula mas grande? Hay un límite?

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El estudio de las células también implica analizar la información de la biodiversidad y la complejidad de la organización celular en los organismos: aún falta mucho por descubrir!

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¿Por qué las células en general son pequeñas? VOLUMEN afecta la velocidad de producción de calor / consumo de

recursos

AREA SUPERFICIAL afecta la velocidad de intercambio de materia y energia con el entorno

Al aumentar el tamaño celular, disminuye la relación área superficial/volumen

Las tasas metabólicas se incrementan mas rápido que la habilidad del area superficial de intercambiar sustancias, lo que limita el volumen final.

La relación área superficial/volumen limita el tamaño de una célula SOLUCION: CÉLULAS PEQUEÑAS!

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Existen además adaptaciones en las células para mejorar el intercambio de materia y energía

Pelos en la raíz de una planta vascular

Células de la cóchlea humana

La forma: glóbulos rojos

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Organismos uni versus multicelulares

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¿Podemos hablar de combinaciones aún más complejas?

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Cell 158, 705–721 (2014)

These studies characterize important variables in early-life microbe-host metabolic interaction and identify several taxa consistently linked with metabolic alterations

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Virus, Viroides y Priones

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The Seven Pillars of Life are the essential principles of life described by Daniel E. Koshland in 2002 in order to create a universal definition of life. The seven pillars are

Program

Improvisation

Compartmentalization

Energy

Regeneration

Adaptability

Seclusion

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Program An organized plan that describes both the ingredients themselves and the kinetics of the interactions among ingredients as the living system persists through time.

Improvisation Ability to change its program in response to the larger environment in which it exists. An example of improvisation on earth is natural selection. Compartmentalization Separation of spaces in the living system that allow for separate environments for necessary chemical processes. Compartmentalization is necessary to protect the concentration of the ingredients for a reaction from outside environments. Energy Because living systems involve net movement in terms of chemical movement or body movement, and lose energy in those movements through entropy, energy is required for a living system to exist. Regeneration General compensation for losses and degradation in the various components and processes in the system. Living systems replace these losses by importing molecules from the outside environment, synthesizing new molecules and components, or creating new generations to start the system over again. Adaptability Ability of a living system to respond to needs, dangers, or changes. It is distinguished from improvisation because the response is timely and does not involve a change of the program. Adaptability occurs from a molecular level to a behavioral level throughfeedback and feedforward systems. For example, an animal seeing a predator will respond to the danger with hormonal changes and escape behavior. Seclusion Separation of chemical pathways and the specificity of the effect of molecules, so that processes can function separately within the living system. In organisms on Earth, proteins aid in seclusion because of their individualized structure that are specific for their function, so that they can efficiently act without affecting separate functions.

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The First Cell arose in the previously pre-biotic world with the coming together of several entities that gave a single vesicle the unique chance to carry out three essential and quite different life processes. These were: (a) to copy informational macromolecules, (b) to carry out specific catalytic functions, and (c) to couple energy from the environment into usable chemical forms. These would foster subsequent cellular evolution and metabolism. Each of these three essential processes probably originated and was lost many times prior to The First Cell, but only when these three occurred together was life jump-started and Darwinian evolution of organisms began. (Koch and Silver, 2005)

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Organización celular en EUCARIOTAS

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Membranas biológicas

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Membranas biológicas

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Membranas biológicas

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