Cell Bio Exam 2 Lecture 6 Flashcards
(29 cards)
Water is important for its role in ordering the
________ ________ that form
________ ________
amphipathic phospholipids, membrane bilayers
Formation of _______
is energetically favored in aqueous environments
closed vesicles
Cholesterol is an amphipathic molecule T or F
True
Two of the major components of the lipid bilayer
Phospholipids, cholesterol
What are the 3 major phospholipds?
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
Which of the following movement(s) occurs least frequently for phospholipids in membrane bilayers:
Lateral movements within the plane of the same bilayer
Flexion along their long axis
Rotation about their long axis
Movement into the other leaflet of the bilayer
Movement into the other leaflet of the bilayer
Dynamics of phospholipids
Rotation, lateral diffusion, Flip-flop (rarely occurs)
Proteins that aid the movement of phospholipids from one leaflet of a membrane bilayer to another are known as:
Flippases
Membrane fluidity depends on
composition and length of the phospholipid hydrocarbon tails
An increase in cholesterol content will tend to make membranes:
Less permeable and less flexible
Cholesterol is also important to the formation of
lipid rafts
Cholesterol forming lipid rafts are….
enriched in signaling proteins whose diffusion is more limited
Membranes are more fluid in nature when hydrocarbon tails are ___ and ___.
unsaturated, short
Of the following choices regarding hydrocarbon tails, which would be the least fluid?
no double bonds and 16 carbons long
no double bonds and 20 carbons long
one double bond and 16 carbons long
one double bond and 20 carbons long
None of the above – only cholesterol determines fluidity
no double bonds and 20 carbons long
Where are membrane phospholipids first synthesized and inserted into membranes?
The cytosolic surface of the ER
What are Scramblases?
catalyzes transfer of random phospholipids from one monolayer to another
What are flippases?
catalyzes transfer of specific phospholipids to cytosolic monolayer
T or F: All transmembrane proteins float and diffuse freely in the bilayer of the plasma membrane in the same manner as phospholipids
False
T or F: Eukaryotic cells have membrane compartments whose lipid bilayers are typically asymmetric with regard to the distribution of their contents between the two leaflets of the bilayer
True
vesicle docking and fusion establishes
polarity and asymmetry of the contents
_____ and _____ occur only or mainly in the outer leaflet of the plasma membrane because….
Glycolipids, glycoproteins
because of their synthesis on the interior face of the Golgi
What are the 3 mechanisms for membrane localization of proteins?
Integral membrane proteins, lipid anchor addition, and peripheral membrane proteins
In transmembrane domains, hydrogen bonds in alpha helices
“occupy” dipoles in peptide bonds hydrophobic R groups
What are examples of transmembrane domains?
bacteriorhodopsin (transmembrane a helix), mitochondrial porin (beta barrel)
