Biochemistry Ch. 12- Membrane Structure

Cholesterol

buffers the membrane fluidity so it does not get too fluid or rigid

Peripheral proteins

proteins that associate with the hydrophilic face

Integral proteins

proteins that associate with the hydrophobic interior, usually a-helices

Lateral diffusion in membranes

lipids and proteins rapidly diffuse in the membrane (bleaching one spot rapidly goes away) 

Transverse diffusion in membranes

slow, but can happen with the help of enzymes, the prohibition accounts for the stability of membrane asymmetry (outside stays outside, inside stays inside)

Channels and carriers

allow for facilitated diffusion or passive transport

Active transport

pumps move molecules against their concentration gradient using ATP

Secondary Active transport

uses the gradients set up by active transport to pump molecules across the membrane (piggyback it)

Selectivity filter in ion channel

a molecule must be small enough to pass through. It must also be able to have weak interactions with the selectivity filter to make it energetically favorable to pass through

Hard-Knock model of Potassium ion channel

Newton’s cradle, where K pushes a line through

Knock-On model of a potassium ion channel

involves water in the line