Chapter 11 - Lipids Flashcards
. Plant membranes have a higher percentage of unsaturated fatty acids than animal membranes.Animal membranes are ( less or more) fluid than plant membranes.
less fluid (more rigid)
Name an important representative of a steroid.
cholestrol
Where does most new membrane synthesis take place in a eukaryotic cell?
ER
In addition, the more closely packed the fatty acid tails, the ____ fluid the membrane; ________ fatty acid tails have no double bonds and can pack more closely together.
less; saturated
Membranes ____ their orientation during transfer between cell compartments.
retain
There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the **most highly mobile** phospholipid (listed as # of carbons and # of double bonds, respectively)? a) 24 carbons with 1 double bond; b) 15 carbons with 2 double bonds; c) 20 carbons with 2 double bonds; d) 16 carbons with no double bonds
b) 15 carbons with 2 double bonds;
In the Golgi and other cell membranes, phospholipid distribution is ____.
asymmetric
Which type of lipids are the most abundant in the plasma membrane?
phospholipids
The association of membrane proteins with lipids in the membrane bilayer always involves _____.
hydrophobic interactions
Lipid molecules in biological membranes are arranged as a continuous double layer called the ______________, which is about 5 nm thick.
lipid bilayer
- A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)?
long, saturated fatty acid tails
Membranes are transported by a process of ______ and ______. Here, a vesicle is shown budding from the Golgi apparatus and fusing with the plasma membrane. Note that the orientations of both the membrane lipids and proteins are preserved during the process: the original cytosolic surface of the lipid bilayer (green) remains facing the cytosol, and the noncytosolic surface (red) continues to face away from the cytosol, toward the lumen of the Golgi or transport vesicle—or toward the extracellular compartment. Similarly, the glycoprotein shown here remains in the same orientation, with its attached sugar facing the noncytosolic side.
vesicle budding; fusing
Sugar containing lipids called _________________________ are found only in the outer half of the bilayer and their sugar groups are exposed at the cell surface.
glycolipids
Name a lipid that is a fused ring compound.
steroids
There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called __________________ proteins and have __________________ regions that are exposed to the interior of the bilayer.
transmembrane; hydrophobic
Enzymes called ______ then randomly transfer phospholipid molecules from one monolayer to the other, allowing the membrane to grow as a bilayer.
scramblases
Which of the following membrane lipids does not contain a fatty acid tail?
cholesterol
Membrane lipids are capable of many different types of movement. Which does not occur spontaneously in biological membranes?
switching between lipid layers
The ____ the fatty acid tail, the more tendency for interaction between the tails, which _____ the fluidity of the membrane.
longer; reduces
When membranes leave the ER and are incorporated in the Golgi, they encounter enzymes called _____ , which selectively remove phosphatidylserine and phosphatidylethanolamine from the noncytosolic monolayer and flip them to the cytosolic side.
flippases
There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the *least organized* phospholipid (listed as # of carbons and # of double bonds, respectively)? a) 24 carbons with 1 double bond; b) 15 carbons with 2 double bonds; c) 20 carbons with 2 double bonds; d) 16 carbons with no double bonds
b) 15 carbons with 2 double bonds;
We can estimate the relative mobility of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for?
FRAP: Fluorescence recovery after photobleaching
We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for?
FRAP: Fluorescence recovery after photobleaching
Eukaryotic plasma membranes contain especially large amounts of ___________________, which enhances the mechanical stability of the lipid bilayer.
cholesterol
