Exam 4 (Topic 18) Flashcards
About 50% of the mass of membranes
Proteins
Membrane proteins can be
Transporters
Anchors
Receptors
Enzymes
Associate with the hydrophobic lipid interior
Hydrophobic regions
Associate with the aqueous cytosol and extracellular environment
Hydrophilic regions
Contain hydrophobic and hydrophilic regions
Transmembrane Proteins
The peptide backbone of proteins is
Hydrophilic (polar)
To span a membrane, this much be protected from the hydrophobic tails
Most common transmembrane protein structure
Transmembrane alpha-helix
What stabilizes the helix in the transmembrane alpha-helix?
Hydrogen bonding between the peptide backbone
The aloha helix maximizes the
number of H bonds possible
The hydrophobic amino acid side chains are
exposed to the lipid bilayer
Can form and channel (pore)
Multi-pass transmembrane proteins
Pores can be formed from
amphipathic alpha-helices
Transmembrane alpha helices can be
Single pass or Multi pass
Proton pump in archae bacteria found in salt marshes
Bacteriorhodopsin
Utilizes energy directly through sunlight
Bacteriorhodopsin
Contains retinal
Bacteriorhodopsin
Single light absorbing nonprotein molecule
Retinal
Retinal
Absorbs sunlight, changes confrormation and moves H+ across its polar interior to the outside of the cell
Seven helices
Bacteriorhodopsin
Beta sheets that span the membrane and create transmembrane channels
Beta-barrel
Formed from amphipathic Beta-sheets
Beta-barrel
The majority of the protein is in the cytosol but associated with the inner leaflet an amphipathic alpha-helix
Monolayer-associated proteins