MBB231 - Membranes Pt.1

where do the polar head groups face in a lipid bilayer

on the outside of the lipid bilayer where it interacts with the aqueous solution

what stabilizes the bilayer

• van der waal interactions in the fatty acyl chains

• ionic + hydrogen bonds between the polar head groups and water

what is the purpose of the lipid bilayer + membrane proteins

lipid bilayer - structural backbone and barrier that prevents random movements of material in or out of the cell

membrane proteins - carryout the more specialized functions

how do specialized or differentiated cell types have unique properties

they have unique properties from different expressions of distinct groups of membrane proteins

what factors determine the lipid-to-protein ratio

• type of cellular membrane

• type of organism

• type of cell

what are the functions of membranes

• compartmentalization - surrounds cells + organelles and allows different regions of the cell to have specialized activities

• scaffold for biochemical activities - organizes enzymes, receptors, and signaling molecules into ordered spatial frameworks

• selective permeability - impermeable to most molecules without the help of specialized transport proteins → has machinery to transport most molecules across the membrane

• responds to external signals - plasma membranes contain receptors that allow cells to respond to signals from their environment → allows cells to communicate with each other

• important in production of energy - are found on organelles that produce energy (chloroplasts + mitochondria)

what are the three types of lipids

• phosphoglycerides

  • glycerol backbone + phosphate group + polar head group + 2 fatty acid chains

• sphingolipids

  • sphingosine + phosphate group + polar head group + fatty acid chain

• sterols

  • has 3 cyclohexane rings + 1 cyclopentane ring

out of the three lipids which one is the most abundant in most membranes

phosphoglycerides are the most abundant in most membranes → unique amphipathic structure allows them to spontaneously assemble into a stable lipid bilayer in an aqueous environment

what kind of bonds are used to link a glycerol to the polar head group

phosphodiester bond

what are the 3 different types of phosphoglycerides + what are the net charges for each one

• phosphatidylethanolamine (zero)

• phosphatidylserine (negative charge)

• phosphatidylcholine (zero)

what is a phosphatidylinositol (PI)

a kind of phosphoglycerides (glycerophospholipid) that has an important role in signal transduction

what is the base structure of a sphingolipid

a ceramide (sphingosine + fatty acid chain)