Chapter 11 Flashcards
(26 cards)
Which is NOT found in a cell membrane? A: Lipid B: DNA C: Protein D: Cholesterol
B: DNA
The cell membrane is NOT involved in:
DNA replication
The tails of phospholipids are:
hydrophobic
The entire phospholipid molecule is:
amphipathic
Which parts of the phospholipid face the outside of the membrane?
The head
Why do lipids form bilayers in water?
The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
In a lipid bilayer, which behaves like a two-dimensional fluid, lipids rapidly diffuse:
within the plane of one monolayer in the bilayer.
In one second, a lipid in an artificial bilayer may diffuse as far as what distance?
2 microns (the length of a large bacterial cell)
Phospholipids with which of the following hydrocarbon tails will produce the most fluid bilayer?
Tails with 18 carbon atoms and two double bonds
Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment?
The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms)
Double bonds in hydrocarbon tails have what effect on the rigidity of fats and phospholipid bilayers?
Double bonds decrease the ability of hydrocarbon tails to
pack together into a rigid mass.
How does cholesterol in animal cell membranes affect the fluidity of the bilayer?
Cholesterol tends to stiffen the bilayer.
In eukaryotic cells, new phospholipids are manufactured by enzymes bound to which part of the endoplasmic reticulum membrane?
The monolayer that faces the cytosol
What type of enzyme moves phospholipids from one monolayer to the other in a biological membrane?
Flippase
When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face:
outside the cell
How much of the mass of the plasma membranes is constituted by proteins?
50%
Q: Which of the following is NOT a function of membrane proteins?
Generate the energy required for lipids to diffuse through
the membrane
Which is NOT an integral membrane protein?
A: A transmembrane protein that spans the lipid bilayer
B: A monolayer associated protein tucked into the inner leaflet of the lipid bilayer
C: A protein attached to the membrane by non-covalent
interactions with other membrane proteins
D: A lipid-linked protein anchored to the outer leaflet of the membrane
C
In the /alpha helices of transmembrane proteins, the hydrophobic side chains are facing:
the outside of the membrane-spanning helix.
Porin proteins—which form large, water-filled pores in mitochondrial and bacterial membranes—fold into /beta barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?
Hydrophobic
Which statement about phospholipids and detergents is NOT true?
A: Phospholipids have two hydrocarbon tails, whereas detergents have just one.
B: Phospholipids are amphipathic, whereas detergents are hydrophobic.
C: Phospholipids form bilayers, whereas detergents tend to form micelles.
B
Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what?
Pump H+ out of the cell and generate a H+ gradient across the plasma membrane
The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called:
cell cortex
Which is not a mechanism for restricting the movement of proteins in the membrane?
Coating proteins with carbohydrates
