Term 1- Lec 6- Membrane Transport Flashcards
What type of molecules pass the cell membrane via simple diffusion?
Small, non-polar (hydrophobic) molecules
What are the two types of membrane proteins that mediate transport?
Channel and Carrier proteins
Another name for Passive Diffusion
Facilitated Diffusion
Passive transport
Does not require energy and the molecules move down their concentration/electrochemical gradients
Direction of molecules in Active Transport
Against their respective gradients
T/F: Uncharged molecule transport is determined by their concentraion and electrochemical gradients
FALSE; Uncharged molecules do not have a charge therefore an uneffected by electrochemical gradients.
The types of active transport and their differences
- 1º active transport: Uses ATP as it’s E source
* 2º active transport: Uses E from an electrochemical gradient.
T/F: Channel proteins bind to thier solutes
False; their solutes pass through them as long as their open.
Acetylcholine-gated ion channels
Located in muscle cells, when acetylcholin binds to the channel, the gate opens and Na+ enters the cell
Uniport Carriers
A single molecule moves
Symport Carriers
Simultaneous transport of 2 different molecules. A form of Coupled Transport
Antiport Carriers
Transport of two different molecules in opposite directions. aka “Exchangers”. A form of Coupled Transport
The GLUT protein family proteins are what type of __-port carrier
They are all Uniporters
The GLUT protein family proteins exhibit what kind of transport
Passive Transport—Carrier Proteins
Low Km = what affinity
High affinity
High Km = what affinity
Low affinity
Location of GLUT1
Brain, Erythrocyte, placenta, fetal tissue
Location of GLUT2
Liver, Kidney, Intestine, Pacreatic ß-cells
Location of GLUT3
Brain
Location of GLUT4
Muscle, adipose tissue.
Km of GLUT1
High affinity/ Low Km- allows for constant uptake
Km of GLUT2
Low affinity/ High Km
Km of GLUT3
High affinity/ Low Km- allows for constant uptake
Km of GLUT4
Intermediate affinity (insulin regulated). They are recruited to cell surface by insulin signal
What is unique about GLUT4 compared to the rest of it’s protein family?
GLUT4 is not always present on it’s cell’s surfaces. It is insulin-regulated. It is in vesicles awaiting an insulin signal to bring it to the surface.
Tight Junctions do what two things in epithelial cells?
- Establish directionallity in cells
2. Prevent apical proteins from migrating to basolateral locations (establishing direction)
Glucose transport between adjacent cells
Paracellular Transport
Glucose transport in via apical membrane and out via basolateral membrane
Transcellular Transport
What are the three membrane proteins used in Glucose transport from lumen to bloodstream? What type of transport are they?
Apical: Na-Glucose Transporter—2º active transport—Symport
Basolateral: Na/K ATPase—1º active transport—Antiport & GLUT2—Passive transport—Uniport
Movement of Na+ at apical surface
2 Na+ move Into the enterocyte ALONG it’s gradient. E used to move Glucose into enterocyte
Movement of Na+ at basolateral membrane
3 Na+ move out of the enterocyte AGAINST it’s gradient. Uses ATP to maintain Na+ gradient.
Movement of K+ and where does this occur
Basolateral membrane. 2 K+ moves into the enterocyte.
