What does the fluid mosaic model describe?
A fluid phospholipid bilayer with proteins embedded in it or attached to its surface.
Which lipid is most abundant in the plasma membrane?
Phospholipids.
How often do adjacent phospholipids switch places within a bilayer?
About times per second.
Why do membrane proteins move more slowly than lipids?
They are larger.
Where do integral proteins penetrate the membrane, and where do peripheral proteins bind?
Integral proteins penetrate the hydrophobic core; peripheral proteins bind to the surface or other membrane proteins.
What property lets a plasma membrane regulate molecular traffic selectively?
Selective permeability.
How do hydrophobic nonpolar molecules cross the lipid bilayer?
They dissolve in it and cross rapidly.
What defines passive transport across a membrane?
A substance diffuses down its concentration gradient without energy investment.
How does diffusion move molecules when no other forces act?
From higher to lower concentration without energy input.
What membrane-building role do the endoplasmic reticulum and Golgi apparatus perform?
They establish the asymmetric distribution of membrane proteins, lipids, and associated carbohydrates.
Answer 11 questions on Membrane Structure and Transport.
1. Which arrangement is described by the fluid mosaic model of a cell membrane?
2. What feature makes a phospholipid amphipathic?
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