The fluidity of the lipid side chains in the interior of a bilayer is generally increased by a decrease in temperature
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F
F
Which of these statements about the composition of biological membranes is false?
A) In a given eukaryotic cell type (for example, a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins.
B) The carbohydrate found in membranes is virtually all part of either glycolipids or glycoproteins.
C) The plasma membranes of the cells of vertebrate animals contain more cholesterol than the mitochondrial membranes.
D) The ratio of lipid to protein varies widely among cell types in a single organism.
E) Triacylglycerols are not commonly found in membranes.
A) In a given eukaryotic cell type (for example, a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins.
The type of motion least common in biological membranes is:
A) flip-flop diffusion of phospholipid from one monolayer to the other.
B) lateral diffusion of individual lipid molecules within the plane of each monolayer.
C) lateral diffusion of membrane proteins in the bilayer.
D) lateral diffusion of protein molecules in the lipid bilayer
E) random motion of the fatty acyl side chains in the interior of the phospholipid bilayer.
A) flip-flop diffusion of phospholipid from one monolayer to the other.
Which of these statements is generally true of integral membrane proteins?
A) A hydropathy plot reveals one or more regions with a high hydropathy index.
B) The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.
C) They are unusually susceptible to degradation by chymotrypsin.
D) They can be removed from the membrane with high salt or mild denaturing agents.
E) They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.
A) A hydropathy plot reveals one or more regions with a high hydropathy index.
The inner (plasma) membrane of E. coli is about 75% lipid and 25% protein by weight. Approximately how many molecules of membrane lipid are there for each molecule of protein? (Assume that the average protein is Mr 50,000 and the average lipid is 750.)
A) 1
B) 50
C) 200
D) 10,000
E) 50,0000
C) 200
A hydropathy plot is used to:
A) determine the water-solubility of a protein.
B) deduce the quaternary structure of a membrane protein.
C) determine the water content of a native protein.
D) extrapolate for the true molecular weight of a membrane protein.
E) predict whether a given protein sequence contains membrane-spanning segments.
E) predict whether a given protein sequence contains membrane-spanning segments.
The shortest α helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.(This is another critical thinking question. Hint: Look at the figure describing a turn in an alpha helix. Find the length of a lipid bilayer)
A) 5
B) 20
C) 50
D) 100
E) 200
B) 20
Which one of the following statements about membranes is true?
A) Most plasma membranes contain more than 70% proteins.
B) Sterol lipids are common in bacterial plasma membranes.
C) Sterol lipids are common in human cell plasma membranes.
D) Sterol lipids are common in plant cell plasma membranes.
E) The plasma membranes of all cell types within a particular organism have basically the same lipid and protein composition.
C) Sterol lipids are common in human cell plasma membranes.
When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by putting more unsaturated fatty acids into its membranes.
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Membrane proteins:
A) are sometimes covalently attached to lipid moieties.
B) are sometimes covalently attached to carbohydrate moieties.
C) are composed of the same 20 amino acids found in soluble proteins.
D) diffuse laterally in the membrane unless they are anchored.
E) have all of the properties listed above.
E) have all of the properties listed above.
Which of the fatty acids has the higher melting temperature?
A) 18:1Δ9
B) 18:2Δ9,12
C) 16:0
D) 18:0
D) 18:0
Which of the following is not a fat-soluble vitamin?
A
C
D
E
K
C
Which of the following statements is true of lipids?
A) Many contain fatty acids in ester or amide linkage.
B) Most are simply polymers of isoprene.
C) Testosterone is an important sphingolipid found in myelin.
D) They are more soluble in water than in chloroform.
E) They do not play a significant role as energy-storage molecules.
B) Most are simply polymers of isoprene.
Lipids are large polymers
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Fatty acids are strongly hydrophilic
A) True
B) False
B) False
Sterols are found in the membranes of all living cells.
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F
F
All other things being equal the more unsaturation, the lower the melting temperature
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F
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All other things being equal, the longer the acyl chain, the higher the melting temperature
A) True
B) False
A) True
Which of the following molecules or substances contain, or are derived from, fatty acids?
A) Beeswax
B) Prostaglandins
C) Sphingolipids
D) Triacylglycerols
E) All of the above contain or are derived from fatty acids.
E) All of the above contain or are derived from fatty acids.
Which of the following best describes the cholesterol molecule?
A) Amphipathic
B) Nonpolar, charged
C) Nonpolar, uncharged
D) Polar, charged
E) Polar, uncharged
A) Amphipathic