Membrane Basics and Lipids Flashcards
(22 cards)
What is the composition of a membrane?
Proteins, lipids, carbohydrates
Functions of lipids
Energy storage, Insulation, water repellent, membrane structure, cofactors for enzymes, signaling molecules, pigments, antioxidants.
How are lipids classified?
Based on structure and function. Whether they have fatty acids or not.
What’s special about unsaturated cis fatty acids?
• Unsaturated cis fatty acids pack less orderly due to the kink – less-extensive favorable interactions
(Creates space in membrane that can harbor proteins)
Lower melting point.
How are unsaturated trans fatty acids formed and why are they used?
Formed by partial dehydrogenation of unsaturated fatty acids
– Done to increase shelf life or stability at high temperature of oils used in cooking (especially deep frying)
How do we store fat?
Triacylglycerols
What is the major component of cell membranes ?
Phosphatidylcholine
Why is it advantageous that most prokaryotes cant synthesize phosphatidylcholine?
Many prokaryotes, including E. coli, cannot synthesize this lipid; their membranes do not contain phosphatidylcholine. Advantageous bc eukaryotic membrane triggers immune response if exposed to them.
A fatty acid is joined to sphingosine to form sphingolipids via a what linkage?
Amide linkage
Where is sphingomyelin abundant?
Myelin sheath that surrounds some nerve cells
Changing the length of the carbon chain changes what?
Membrane thickness.
What is a vesicle or liposome?
Small bilayers will spontaneously seal into spherical vesicles. They contain artificially inserted proteins. Vesicles fuse readily with cell membranes or with each other.
How do membranes form spontaneously?
Form spontaneously in aqueous solution and are stabilized by noncovalent forces, especially hydrophobic effect
Difference between integral and peripheral proteins?
- Integral proteins are firmly associated with the membrane, often spanning the bilayer.
- Peripheral proteins are weakly associated and can be removed easily – Some are noncovalently attached – Some are linked to membrane lipids
Serine is a what?
Alcohol
What does it mean that the membrane layers are asymmetric?
Two leaflets have different lipid compositions
Outer leaflet is often more positively charged
• Phosphatidylserine outside has a special meaning:
– Platelets: Activates blood clotting
– Other cells: Marks the cell for destruction
Membrane needs to be in what phase for proper function?
Fluid-like rather than gel-like.
What do the membranes need to maintain integrity and fluidity of the membrane at diff temps?
- At higher temperatures cells need more saturated fatty acids – To maintain integrity
- At lower temperatures cells need more unsaturated fatty acids – To maintain fluidity
Flippases do what?
Flippases—catalyze transverse diffusion
• Some flippases use energy of ATP to move lipids against the concentration gradient
Flippase - in ( moves from outer to side of cytosol)
Floppase- out ( from cytosol to outer leaflet)
Scamblase - moves lipids in either direction toward equilibrium
How does cholesterol in the membrane move?
moves from one place to another in lipid rafts.
What are lipid drafts?
membrane subdomains enriched in certain lipids and proteins
Proteins and lipids in the membrane are held together by what interactions?
non covalent interactions
