Membranes and Transporters Flashcards
What is the general structure of a typical membrane lipid and what are its “parts”?
Long hydrocarbon chain w/ carboxylic acid group
What is meant by membrane fluidity and Tm, and how does the degree of lipid saturation affect Tm and fluidity?
Membrane fluidity - degree of freedom of movement of proteins and lipids that make up cell membrane
Melting temp (Tm) - characteristic temp where lipids incr in fluidity, go from gel-like phase to fluid-like phase
Saturated lipids stacked tightly (rigid, not fluid) via intermolecular interactions, addn of unsaturated lipids disrupts rigidity and incr fluidity
What types of lipid movements are observed in membranes and how do they occur?
What types of membrane asymmetries and composition differences are there, how are they established and maintained, and why might they exist?
“Flip-flop” diffusion - translocation from one leaflet to other side
Flippase - moves lipids to inside
Floppase - moves lipids to outside
Scramblase - collapses any asymmetry
HOW MAINTAINED AND WHY EXIST
How are proteins associated with membranes? How are their movements within membranes affected by the lipid composition of the membrane at any temperature?
How might proteins become concentrated at particular places on the surface of a cell?
For transporters, like the Glucose transporter example, what is happening at each step in the transport mechanism? Describe each step as a kinetic equation.
Glucose binds to receptor/transporter, changes conformation of transporter
Transporter flips with opening on inside, changes affinity for glucose
Glucose pushed out
Transporter flips back to original conformation
Reversible rxn - add phosphate
KINETIC EQUATION
What are the differences between passive, facilitated, and active transport? How are each controlled?
Passive transport - energy independent; solute moves down conc gradient
Facilitated transport - regulated movement down a concentration gradient but across an energy barrier; regulated w/ channels and transporters
Active transport - energy dependent; solute moves against conc gradient
Symporters
Type of coupled transport; 2 solutes must both go in before conformational change occurs
Antiporters
Type of coupled transport; 1 solute in, 1 solute out
Coupled transport
Coupling upward movement of one substrate to downward flow of another substrate
Why are the kinetics different between facilitated and passive transport? What are the energetics that drive each type of transport?
The equation for calculating the free energy of any gradient is ΔG=RTln[C2]/[C1]. How is a difference in concentration of solute on either side of a membrane affecting the direction of flow in passive or facilitated diffusion? How does any charge on the solute contribute to the direction of flow?
Describe the kinetics of the Calcium-ATPase and/or Na+/K+ pump reactions. What does each equation of the kinetics diagram describe?
What does calcium binding do?
