Cell Biology: Chapter 8

Membrane Structure

plasma membrane

enclosing cell

internal membrane

enclosing an intracellular compartment

• form specialized compartments by selective permeability

• asymmetric protein distribution

• control reaction sequences

Membrane Functions

Davson Danielli Model

• lipid bilayer

• proteins coat outer surface

energetically unfavorable

planar phospholipid bilyaer with edges exposed to water

energetically favorable

sealed compartment formed by phospholipid bilayer

phospholipid

most abundant membrane lipid

polar groups

phosphate has additional

hydrophilicity

phosphate increases

saturated; unsaturated

phospholipid has both ____ and ___ fatty acids

ceramides and sphingolipids

amino alcohols with fatty acid chains

Cholesterol steroid

• 50% of animal plasma membrane

• hydrophilic OH group toward surface

• small and less amphipathic

  • enhances permeability barrier

asymmetrically

lipids distributed asymmetrically

glycolipid

lipid with a sugar head

fluid

membrane is

sideways (laterally)

lipids move rapidly

flip flop

lipids ___ ___ across bilayer extremely slowly

flex (move side to side)

lipid tails

lipid composition

fluidity depends on

tight packing

fluidity depends on

melt at a lower temperature

unsaturated (cis not trans)

short chains

___ ___ melt at lower temperature

cholesterol (animal)

fills space between fatty acid tails

lateral protein diffusion

membrane fluidity allows ___ ___ ___ in membrane

membrane carbohydrates

face away from cytoplasm

• outside plasma membrane

oligosaccharide

glycprotein has

• attached to asparagone N;linked