Cell Membranes And Transporters

Question 1

Phosphoglycerides

Answer 1

Have a kink that prevents tight packing and increases fluidity; cells less likely to freeze
*Phosphatidyl-Serine has a negative charge, involved with C2 activation in PKC (Gq-alpha pathway)

Question 2

Sphingolipids

Answer 2

Have a sphingosine backbone
Example is spingomyelin found in neurons. Can be seen in “Lipid Rafts”
Can have attachments to the amine group.

Question 3

Sterols

Answer 3

Keeps the PM “rigid”, stiffens regions of PM (lipid rafts)

Example is cholesterol.

Question 4

Glycolipids

Answer 4

Usually has sphingosine backbone, carbohydrate is always on EXTERNAL face; OUTER LEAFLET PM; have 40 types of gangliosides, that are charged and are derived from sugars rather than phosphate
Cholera toxin binds to this for entry

Question 5

Uniporter

Answer 5

A type of carrier transporter that takes one molecule down gradient
Ex: GLUT 1 uniporter on basal side of GI epithelial cells

Question 6

Symporter

Answer 6

Carrier that couples the movement of one molecule with another (w/o NRG),
Ex: Na+/Glucose transporter in the brain

Question 7

Antiporter

Answer 7

Couples the downward movement of one molecule with the unfavorable movement of another (w/o NRG)
Ex: Na+/Ca2+ antiporter in cardiac cells of the heart

Question 8

P-Type Active Transporter

Answer 8

ATP-driven pump that auto-PHOSPHORYLATES for conformational change and pump ions
Type 1 - Ca2+ ATPase in muscle cells, reestablish Ca2+ release in muscle contraction
Type 2 - Na+/K+ ATPase in neurons, maintain a gradient for action potentials, K+ pumped out and Na+ is pumped inward

Question 9

ABC Transporter

Answer 9

ABUNDANT transporter in the body; known for exporting SMALL MOLECULES in eukaryotes;
2 ATPases dimerize, conformational change, ATP hydrolysis and release of substrate;
MDR and chloroquine resistance in cancer cells and malaria, respectively

Question 10

This transporter _____________ drives the opening and closing of a Cl- channel. It’s ligand is _____. The disease associated with the transporter is _______________. We have a build up of ___________.

Answer 10

CFTR,
ATP,
Cystic Fibrosis (deletion in amino acid 508)
Thick mucus

Question 11

What distinguishes these transporters?
Pumps
Carriers
Channels

Answer 11

Pumps - most SPECIFIC and SLOW; energy-dependent
Carriers - intermediate specificity and rate; passive transport
Channels - most RAPID rate; regulated by open/closed pores

Question 12

Lipid Rafts

Function and components

Answer 12

Create an environment for protein association (ex: G-alpha-q and PLC in Gq pathway). Composed of cholesterol and sphingomyelin. (Almost like the wood planks and glue of a raft, respectively)

Question 13

Integral proteins

Answer 13

PERMANENTLY incorporated to the membrane. Have buried HYDROPHILIC amino acids;
(Ex: alpha helices, beta barrels, 7-alpha transmembrane domain)
*Related to cell adhesion

Question 14

Peripheral proteins

Answer 14

REVERSIBLE interaction with the membrane. Contain CHARGED, electrostatic amino acids.
(Ex: ECM receptors; glycosylated proteins)
*Related to cellular activation and signaling