Chapter 11 – Membrane structure
Membrane Proteins
Functions of membrane proteins
Transporters & channels; transport nutrient,
ions
Anchors (bevestigen); anchors membrane to
macromolecules on either side
Receptors; detect chemical signal in
environment and relay them into cell interior
Enzymes; catalyze specific reactions at cell membrane
Membrane proteins associate with the lipid
bilayer in different ways
1. Transmembrane; are amphipathic, having
both hydrophobic and hydrophilic regions
o Single pass receptors
o Double or multi pass channels
o Beta-sheet; rolled in a cylinder
called a beta barrel. Found in the
porin proteins which form large, water-filled pores in mitochondrial an
bacterial outer membranes.
2. Monolayer; almost entirely in the cytosol. Associated with half of the lipid layer
by an amphipathic alfa helix
3. Lipid-linked; proteins entirely outside bilayer only covalent bonds attached to
bilayer
4. Protein-attached; other proteins are indirectly bound to proteins in membrane.
Integral membrane proteins; proteins that are directly bound to bilayer
(transmembrane/monolayer/lipid-linked). They can only be removed by disrupting the
bilayer with detergents (reinigingsmiddelen).
Peripheral membrane proteins; not directly bound to bilayer (protein-attached). They
can be removed by extraction procedures that interfere with protein-protein
interactions but leave the lipid bilayer intact.
Polypeptide chain crosses the lipid bilayer as an alfa-helix
Transmembrane proteins contain hydrophobic and hydrophilic sides
The segments which run through the hydrophobic environment of the
interior of the lipid bilayer are composed of amino acids with hydrophobic
side chains.
So, outside is hydrophobic and in the alfa helix there are hydrogen bonds.
Membrane proteins can be removed with detergents (reiningsmiddelen)
First step in removing is solubilizing the membrane that destroy the lipid
bilayer by disrupting hydrophobic associations. This happens by using detergents.
The hydrophobic end of detergent molecule interact with hydrophobic regions of
transmembrane proteins as well as with the hydrophobic tails of the phospholipid
Membrane Proteins
Functions of membrane proteins
Transporters & channels; transport nutrient,
ions
Anchors (bevestigen); anchors membrane to
macromolecules on either side
Receptors; detect chemical signal in
environment and relay them into cell interior
Enzymes; catalyze specific reactions at cell membrane
Membrane proteins associate with the lipid
bilayer in different ways
1. Transmembrane; are amphipathic, having
both hydrophobic and hydrophilic regions
o Single pass receptors
o Double or multi pass channels
o Beta-sheet; rolled in a cylinder
called a beta barrel. Found in the
porin proteins which form large, water-filled pores in mitochondrial an
bacterial outer membranes.
2. Monolayer; almost entirely in the cytosol. Associated with half of the lipid layer
by an amphipathic alfa helix
3. Lipid-linked; proteins entirely outside bilayer only covalent bonds attached to
bilayer
4. Protein-attached; other proteins are indirectly bound to proteins in membrane.
Integral membrane proteins; proteins that are directly bound to bilayer
(transmembrane/monolayer/lipid-linked). They can only be removed by disrupting the
bilayer with detergents (reinigingsmiddelen).
Peripheral membrane proteins; not directly bound to bilayer (protein-attached). They
can be removed by extraction procedures that interfere with protein-protein
interactions but leave the lipid bilayer intact.
Polypeptide chain crosses the lipid bilayer as an alfa-helix
Transmembrane proteins contain hydrophobic and hydrophilic sides
The segments which run through the hydrophobic environment of the
interior of the lipid bilayer are composed of amino acids with hydrophobic
side chains.
So, outside is hydrophobic and in the alfa helix there are hydrogen bonds.
Membrane proteins can be removed with detergents (reiningsmiddelen)
First step in removing is solubilizing the membrane that destroy the lipid
bilayer by disrupting hydrophobic associations. This happens by using detergents.
The hydrophobic end of detergent molecule interact with hydrophobic regions of
transmembrane proteins as well as with the hydrophobic tails of the phospholipid
