Exam 3- Plasma Membrane Flashcards
Why aren’t biological membranes more rigid?
Because they contain phospholipids and allow for the passage of small molecules in and out of the cell.
What property of phospholipids makes them so fluid?
Phospholipid tails have a kink, caused by a double bond or unsaturation. Introduces space allowing transmembrane proteins to move laterally along the membrane.
What’s the main component of the plasma membrane that also determines most of its properties?
Phospholipids
Is the plasma membrane symmetrical? If not, how are phospholipids specifically distributed across the plasma membrane (i.e., which are more abundant inside than outside and vise versa)?
No the plasma membrane is not symmetrical.
Outside only: Glycolipid
Inside only: serine, inositol
[High] Out: sphingomyelin and choline
[High] inside: enthanolamide
[Equal] : cholesterol
How abundant are proteins in membranes?
50% of the PM weight is from proteins.
50-100 lipid molecules to 1 protein
How do proteins associate to the plasma membrane?
either being integral proteins or peripheral membrane proteins
What’s an Integral Membrane Protein?
- transmembrane : single or multiple channels
- membrane associated: domain doesnt fully pass
- lipid linked: GPI anchor, N, C or mid
must disrupt the membrane with detergent
What’s a Peripheral Membrane Protein?
loosely attached, associated to Integral Membrane Proteins
disrupt with high salt and high or low pH
What are Lipid Rafts?
Semi-solid regions in the PM, made of glycolipids, sphingomyelin, cholesterol and enriched in GPI anchors and TM proteins
can associate with cytoskeleton to stabalize and divide the PM
what are the functions of lipid rafts?
cell signaling, movement, endocytosis
what is the size of a lipid raft?
10-200nm
