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Chapitre 5

Membranes et transport cellulaire

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Que sont les membranes ?

A key characteristic of life is the ability to separate the external environment from the internal space. To do this, cells have evolved semi-permeable ...

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Fluidité de la membrane

Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are ...

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Le modèle de mosaïque fluide

The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of ...

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Qu'est-ce qu'un gradient électrochimique ?

Adenosine triphosphate, or ATP, is considered the primary energy source in cells. However, energy can also be stored in the electrochemical gradient of an ...

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Diffusion

Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as ...

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Osmose

Approximately 60% to 95% of the weight of living organisms is attributed to water. Therefore, maintaining appropriate water balance within cells is of ...

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Tonicité chez les animaux

The tonicity of a solution determines if a cell gains or loses water in that solution. The tonicity depends on the permeability of the cell membrane for ...

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Tonicité chez les plantes

Tonicity describes the capacity of a cell to lose or gain water. It depends on the quantity of solute that does not penetrate the membrane. Tonicity ...

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Associations de protéines

The cell membrane, or plasma membrane, is an ever-changing landscape. It is described as a fluid mosaic where various macromolecules are embedded in the ...

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Transport facilité

The chemical and physical properties of plasma membranes cause them to be selectively permeable. Since plasma membranes have both hydrophobic and ...

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Transport actif principal

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or ...

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Transport actif secondaire

One example of how cells use the energy contained in electrochemical gradients is demonstrated by glucose transport into cells. The ion vital to this ...

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Endocytose médiée par les récepteurs

Overview Receptor-mediated endocytosis is a process through which bulk amounts of specific molecules can be imported into a cell after binding to cell ...

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Pinocytose

Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells ...

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Phagocytose

Cells pull particles inward and engulf them in spherical vesicles in an energy-requiring process called endocytosis. Phagocytosis (“cellular eating”) ...

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Exocytose

Exocytosis is used to release material from cells. Like other bulk transport mechanisms, exocytosis requires energy. While endocytosis takes particles ...