Biological Membranes: Structure and Membrane Transport

SUMMARY Progesterone in vitro decreases the rates of glucose uptake and of acetate uptake and oxidation, of lipogenesis from acetate and of oxygen consumption, and reduces the intracellular concentrations of ATP and citrate in slices of luteinized rat ovary incubated in a bicarbonate-buffered medium. The effect on glucose uptake was shown to be due to inhibition by progesterone of the membrane transport of glucose. In view of the steroid concentrations used to elicit these effects in vitro and the known actions of steroids such as progesterone on biological membranes, these observations are thought to be due to non-physiological lytic effects.

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Phospholipids and membrane transport

Canadian Journal of Biochemistry ◽

10.1139/o80-147 ◽

1980 ◽

Vol 58 (10) ◽

pp. 1091-1100 ◽

Cited By ~ 124

Author(s):

P. R. Cullis ◽

B. de Kruijff ◽

M. J. Hope ◽

R. Nayar ◽

S. L. Schmid

Keyword(s):

Membrane Transport ◽

Diffusion Processes ◽

Membrane Lipids ◽

Biological Membranes ◽

Lateral Diffusion ◽

Transport Processes ◽

Functional Abilities ◽

Fusion Event ◽

Membrane Morphology

The ability of membrane lipids to adopt nonbilayer configurations suggests dynamic roles for lipids in many functional abilities of biological membranes. In this work evidence supporting the involvement of lipids in three types of membrane transport process is presented and discussed. These transport processes include facilitated transbilayer transport of polar molecules, transport mechanisms involving fusion events, and transport possibilities arising from alternative membrane morphology. In particular it is shown that lipids such as cardiolipin, which adopt the hexagonal H11 phase in the presence of Ca2+, may be logically proposed to facilitate Ca2+ transport across membranes via an inverted micellar intermediate. Alternatively, in transport processes such as exocytosis the ability of Ca2+ to generate membrane instabilities favouring nonbilayer alternatives suggests a crucial role of phospholipid in the fusion event vital to exocytotic release. Finally, nonbilayer lipid structures may be suggested to favour formation of isolated compartments connected by a continuous membrane where lateral diffusion processes can lead to transport. These various possibilities are summarized in a "metamorphic mosaic" model of biological membranes.

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Membrane Transport in Biology. Volume I (Concepts and Models).D. C. TostesonMembrane Transport in Biology. Volume II (Transport Across Single Biological Membranes).D. C. TostesonMembrane Transport in Biology. Volume III (Transport Across Multi-Membrane Systems).G. Giebisch

The Quarterly Review of Biology ◽

10.1086/411634 ◽

1980 ◽

Vol 55 (1) ◽

pp. 67-68

Author(s):

Paul G. LeFevre

Keyword(s):

Membrane Transport ◽

Biological Membranes ◽

Membrane Systems

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Electron Diffraction of Wet Biological Membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050809 ◽

1974 ◽

Vol 32 ◽

pp. 158-159

Author(s):

S.W. Hui ◽

D.F. Parsons

Keyword(s):

Electron Diffraction ◽

Data Collection ◽

Biological Membranes ◽

Small Areas ◽

Electron Diffraction Technique ◽

Electron Microscopes ◽

Collection Time ◽

Camera Length

The development of the hydration stages for electron microscopes has opened up the application of electron diffraction in the study of biological membranes. Membrane specimen can now be observed without the artifacts introduced during drying, fixation and staining. The advantages of the electron diffraction technique, such as the abilities to observe small areas and thin specimens, to image and to screen impurities, to vary the camera length, and to reduce data collection time are fully utilized. Here we report our pioneering work in this area.

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