Membranes Flashcards
Describe uriporters, symporters, and antiporters.
Uniporters- moves one molecule down concentration gradient
Symporters- moves two molecules in the same direction (co-transport)
Antiporters- moves one molecule down concentration gradient and one up (co-transport)
Which channel allows water to flow?
Aquaporin
How does glucose require all 3 types of transporters in the small intestine?
Symporter- imports glucose using sodium gradient
Antiporter- sodium potassium pump to maintain sodium gradient
Uniporter- catalyses diffusion of glucose out of the cell (down its concentration gradient)
What does amphipathic mean?
Amphipathic = has both hydrophilic and hydrophobic parts
What are peripheral membrane proteins?
Membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer.
They can often be ionically interacting proteins.
What is hydropathy?
Measure of energy needed to pass a segment of polypeptide into water from a solvent
What is an amphipathic helix?
A motif that shows all hydrophobic side chains on one side, so they can face into the fatty acid domain and the hydrophilic side chains on the other side.
What is a coiled coil domain?
Two alpha helices wrapped around each other to form a supercoil.
What is the critical micelle concentration?
The concentration of surfactants above which micelles form and all additional surfactants added to the system go to micelles.
> When talking about detergents
What is Ras and how is it located to the plasma memtbeane?
It is a small GTPase and is located to the plasma membrane by prenyl (a cytosolic lipid modification).
What is prenylation?
The addition of hydrophobic molecules, e.g. prenyl.
What is the nuclear lamina?
A dense fibrillar network in the nucleus of the cells. Made of lamina filaments which are prenylated.
What is the difference between a micelle and a liposome?
Micelle- monolayer of surfactant
Liposome-Bilayer of phospholipids
Why are hydrophobic interactions unfavourable? How is this overcome?
They increase the order (decrease the entropy) of water and makes it thermodynamically unfavourable.
This is overcome by hydrophobic molecules aggregating to reduce the surface area in contact with the water.
Why do water molecules form ice like cages around hydrophobic molecules?
Because there are less H bonding possibilities for each water molecule which therefore increases the bond strength for bonds that they do form
