Lecture 1- Cell Organization Flashcards
(48 cards)
What molecules are selectively permeable to the cell surface membrane?
Small molecules
- ions
- metabolites
What kind of transport moves molecules against its concentration gradient?
Active transport (requires energy)
What is the surface of the cell membrane impermeable to?
Large molecules
- Nucleic acids
- Proteins
What are the 3 predominant phospholipids that compose the membrane?
phosphatidylethanolamine
phosphatidylcholine
phosphatidylserine
Are phospholipids amphipathic or amphoteric?
amphipathic
Key points about detergents
- Can dissolve phospholipid membranes because they are amphipathic
- They are also water soluble at much higher concentrations than phospholipids
What do detergent molecules form in order to remove oily stains?
They form micelles; encompassing the oily hydrophobic portion on its interior
sol state vs. gel state
Sol state tends to be at higher temperatures, and lateral diffusion can proceed rapidly
Gel state is at lower temperatures and PLs diffuse slowly
What is the temperature called at which a bilayer converts from the sol state to the gel state or vice versa?
Transition Temperature (TT)
Bilayers with PLs containing long saturated FA chains have what Transition Temperatures relative to bilayers with PLs containing shorter FA chains or double bonds?
Long saturated FA chains have relatively high TTs
Short FA chains or double bonds (generates kinks) do not interact well and therefore have lower TTs
What type of bases to membrane phospholipids typically have?
Glycerol or sphingosine bases
What is more common in membrane lipids, glycerol or sphingosine based?
glycerol
What part of the cholesterol molecule is the “head” in the membrane?
The hydroxyl group
Describe cholesterol and its relationship with membrane fluidity
Cholesterol reduces the fluidity, unless excessive; then become more fluid because falling apart
Explain phospholipids and cholesterol in relation to “flipping”
phospholipids rarely flip
cholesterol can flip easily
what is permeable to the phospholipid bilayer
small uncharged polar molecules
-O2, CO2, NH3 and water
Where are phosphatidylethanolamine, phosphatidylserine and phosphatidylcholine in relation to which side of the bilayer they are on
Surface facing cytoplasm -phosphatidylethanolamine -phosphatidylserine Outward facing surface -phosphatidylcholine
What does Annexin V bind, and what does it detect?
It binds phosphatidylserine (PS)
Detects one of the earliest events in apoptosis- the externalization of PS in living cells
(soon after apoptosis is induced, PS is translocated from the inner leaflet to the outer leaflet of the plasma membrane)
What type of membrane proteins are bound the tightest? and what type of bond?
Integral proteins
Covalent bonds
What are proteins called that span the membrane once or more times?
Transmembrane proteins
What type of structure do transmembrane proteins typically have?
hydrophobic a-helices
Can transmembrane proteins move laterally?
Yes, as long as they are not bound to another protein
Which molecule moves faster through the plane of the membrane, transmembrane proteins or lipids?
lipids;
transmembrane proteins are large molecules and therefore move slower
What are some functions of integral proteins?
receptors (transmit signals between the cell and its environment) adhesion molecules transporters enzymes signal transduction components (form part of cytoskeleton)
