Exam 3: Biological Membranes and Transport Flashcards
What does the “mosaic model” of biological membranes propose?
“A proposed model that claims that lipids form a viscous, two-dimensional solvent into which proteins are inserted and integrated more deeply or less deeply.”
What are characteristics of integral proteins?
Integral proteins are firmly associated with the membrane and can be found throughout the entire bilayer.
What are characteristics of peripheral proteins?
Peripheral proteins are weakly associated with the surface of the bilayer. They are easily removed and soluble.
(True or False) Outer and inner leaflets have different lipid compositions.
True.
Name the three forms of lipids that make up the lipid bilayer.
Phospholipids, sphingolipids, and sterols.
How are the leaflets of the bilayer different in their composition?
Different organisms, tissues, and organelles all have different ratios of lipids to proteins, types of phospholipids, and abundances of sterols.
What sorts of changes can cause a peripheral protein to dissociate from the membrane?
Changes in salt concentration or pH.
What is required to remove integral proteins from the membrane?
A detergent to disrupt the membrane.
On a hydropothy index, does a positive value denote a hydrophobic residue or a hydrophilic residue?
A positive value denotes a hydrophobic residue.
Typ and Trp are largely found clustered where in an integral protein?
Typ and Trp are largely found clustered at the polar/nonpolar interfaces of the membrane.
Charged residues of an integral protein are found where?
In aqueous domains.
If a protein has a segment of ____ residues, it is a membrane spanning protein.
20.
Lateral diffusion within a leaflet is very _____.
a. fast
b. slow
a. fast
Transverse diffusion across leaflets can be induced by a ______ enzyme.
flippase
What are two methods that flippases may cause transverse diffusion across leaflets?
Energy utilization of ATP or by moving two lipids (one lipid from either side of the membrane) at once.
What are traits that a molecule must have to pass through the bilayer without a transporter?
It must be very small and nonpolar.
Why is there a large energy barrier to be overcome by polar molecules that prevents them from passively diffusing.
Polar molecules must be dissolved, and so the interactions between the bonds must be broken, creating an energy barrier.
Primary active transport moves ___ molecule(s) against their gradient using ______.
1, ATP
Secondary active transport moves ___ molecule(s) against their gradient using _____.
2, an electrochemical gradient (symport or antiport)
Define the variables in the following equation:
ΔG_t = RTln (C_2/C_1 ) + zFΔψ
ΔG_t: The relative free-energy change
R: Gas constant (8.314 J/mol·K)
T: Temperature in kelvin
C_2/C_1: Concentration 2 and concentration 1
z: Charge of the molecule
F: The Faraday constant (95.6 kJ/molV)
ψ: The charge of the membrane in the direction of movement
