Simple diffusion occurs directly through the lipid bilayer for small, non-polar molecules.
The phosphate group is ionized and hydrophilic, ensuring the "head" interacts with the aqueous environment.
Peripheral proteins are bound to the surface, not embedded, making them easier to isolate.
Hormones and other signaling molecules bind to glycoprotein receptors on the cell surface.
The "kinks" created by double bonds prevent tight packing, which lowers the melting point and increases fluidity.
Maintaining concentration gradients against the electrochemical gradient necessitates active transport.
Standard plasma membranes are approximately 7.5 nanometers (or 75 Angstroms) in width.
Cholesterol restricts the lateral movement of phospholipids, thus decreasing fluidity at high temperatures.
Transmembrane pumps (like the Na+/K+ pump) use ATP to change conformation and transport ions.
Amphipathic molecules are essential for forming the bilayer as they interact with both aqueous and non-aqueous environments.
Receptors are usually transmembrane integral proteins that span the membrane to receive signals.
Osmosis is defined as the net movement of water across a membrane driven by a water potential gradient.
Channel proteins provide a physical pathway, whereas carrier proteins undergo conformational changes to transport substances.
In hypertonic environments, the external water potential is lower than the cell, causing water to exit by osmosis.
The membrane is fluid and dynamic, not rigid or crystalline.
By measuring the surface area of extracted lipids, they determined it was twice the surface area of the RBC.
The phospholipid bilayer provides the fundamental hydrophobic barrier essential for cellular compartmentalization.
The two hydrocarbon chains (fatty acids) are non-polar and hydrophobic.
Facilitated diffusion requires either channel or carrier proteins to assist polar molecules.
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