Membrane Transport Flashcards
the fluid mosaic model
The fluid mosaic describes that phospholipids generate the membrane and that phospholipids and the embedded proteins can move laterally in the phospholipid bilayer.
components of the membranes that can be used to modulate the fluidity of plasma membranes
fatty acid composition of membrane lipids and cholesterol.
Glycocalyx
consists of sugar residues found in glycolipids and in glycoproteins. It is outside of the plasma membrane and provides a network-shield and can also be involved with cell-cell recognition
Lipid composition of the plasma membrane of the liver
The plasma membrane contains mainly the glycerophospholipids PC and PE.
The outer leaflet contains mainly PC and spingomyelin.
The inner leaflet contains mainly PE and some PS and PI.
Cholesterol is found in both leaflets.
Passive transport
transporter protein facilitates diffusion of larger molecules, etc. in both directions depending on concentration gradient.
GLUT 1
glucose transporter abundant in blood and the brain
deficiency leads to epilepsy-like seizures, delayed psycomotor development
GLUT 3
Dominant in neurons
GLUT 2
Found in the intestinal mucosal cell toward the portal vein, in the liver, kidney and b-cells of pancreas
GLUT 5
intestinal mucosal cells toward the intestinal lumen,
transports mainly fructose
GLUT 4
insulin-dependent
abundant in fat cells and muscle
stored inside the cell, Insulin mobilizes the transport of GLUT-4 to the plasma membrane where it is aligned and allows influx of blood glucose into the cell
Sodium Potassium Pump
Primary active trasport
Active pumping requiring ATP: 3 sodium ions are pumped out and 2 potassium ions are pumped into cells
can be performed against a concentration gradient
Secondary active transport
Uses the concentration gradient of Na+produced by primary active transport processes.
Uses SGLT transports
Example, Glucose moves into the cell along with the Na+ that is being pumped in via SGLT-1
ABC transporters
ATP Binding Cassette transporter
a specialized gated ion channel consisting of two transmembrane domains (2 groups of six a-helices) that form a closed channel.
•Each is connected to an ATP-binding site. phosphorylation opens the channel
CFTR
cystic fibrosis trans-membrane conductance regulator
A type of ABC transporter that is opened by phosphorylation by Protein Kinase A(PKA) following cAMP action. releasing Cl- into the extracellular space
(in sweat glands CFTR works for re-uptake of Cl-)
Found in the plasma membrane of epithelial cell of lungs, pancreas, liver, digestive tract, and reproductive tract
Cardiolipin
Component of the inner mitochondrial membrane
Cholesterol translocation from outer to the inner membrane of mitochondrial
Activates mitochondrial cholesterol side-chain cleavage
Import protein into mitochondrial matrix
Serves as proton trap for oxidative phosphorylation
