Lodish 8e Ch07 Test Bank PDF

7 *Section 7.1* 1\. The plasma membrane around a eukaryotic cell is composed of: a\. hydrophilic fatty acyl side chains. b\. hydrophobic phospholipids. c\. a phospholipid bilayer. d\. none of the above Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Dif...

7 *Section 7.1* 1\. The plasma membrane around a eukaryotic cell is composed of: a\. hydrophilic fatty acyl side chains. b\. hydrophobic phospholipids. c\. a phospholipid bilayer. d\. none of the above Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 2\. Which of the cellular organelles are enclosed by two cellular membranes? a\. Golgi b\. lysosome c\. nucleus d\. endoplasmic reticulum Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 3\. Sphingolipids are considered amphipathic glycolipids if: a\. their polar head groups are sugars that are not linked to the tails via a phosphate group. b\. they are phospholipids with a one-chain hydrophobic tail. c\. have one fatty acyl chain attached to carbon 2 of glycerol. d\. none of the above Ans: a Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Hard 4\. An investigator wants to use FRAP to quantify the lateral movement of a specific plasma membrane protein, but to do so this investigator must first: a\. focus a laser on one region of the cell surface. b\. measure the intensity of the fluorescence of the cell surface. c\. label the cell with a fluorescent reagent that binds specifically to the cell surface. d\. add detergents to make the cell surface more fluid. Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Applying, Analyzing Difficulty: Moderate 5\. Which two organelles are responsible for producing phospholipids and sphingolipids? a\. mitochondria and proteasome b\. endoplasmic reticulum and mitochondria c\. Golgi complex and persoxisome d\. endoplasmic reticulum and Golgi complex Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 6\. When using immunofluorescence microscopy with labeled Annexin V antibodies you found that there is a change in the distribution of the fluorescence when the cells were treated with tumor necrosis factor, an apoptosis-inducing agent. Your data show that this increase in Annexin V fluorescence increases specifically in the: a\. mitochondria. b\. exoplasmic face of the plasma membrane. c\. Golgi. d\. endoplasmic reticulum. Ans: b Question Type: Multiple Choice Chapter: 7 Blooms: Applying, Analyzing Difficulty: Difficult 7\. Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are a\. amphipathic. b\. steroid derivatives. c\. entirely hydrophobic. d\. phospholipid derivatives. Ans: a Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 8\. All the following statements describe biomembranes except: a\. Different biomembranes may contain different proportions of the same phospholipids. b\. The two leaflets of a biomembrane may contain different phospholipids. c\. Some biomembranes have free edges. d\. Some phospholipids and cholesterol may cluster to form lipid rafts. Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 9\. Which of the following classes of lipids is (are) present in biomembranes? a\. phosphoglycerides b\. sphingolipids c\. sterols d\. all of the above Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 10\. Phospholipids with short or unsaturated fatty acyl chains a\. decrease membrane fluidity. b\. increase membrane fluidity. c\. cause biomembranes to become thicker. d\. allow hydrophilic molecules to diffuse across the lipid bilayer. Ans: b Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 11\. Lipid droplets arise from the a\. endoplasmic reticulum. b\. plasma membrane. c\. cytosol. d\. exoplasm. Ans: a Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 12\. How do animal cells maintain membrane fluidity, and hence membrane function, in response to decreased temperature? Ans: Membrane fluidity normally decreases with decreasing temperature and the bilayer becomes more gel-like. To maintain sufficient fluidity and hence function, animal cells could increase the ratio of unsaturated to saturated phospholipids in the membrane. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 13\. What experimental evidence supports the fluid mosaic model of biomembranes? Ans: Results from fluorescence recovery after photobleaching (FRAP) experiments have demonstrated the two-dimensional movement of membrane components and allow quantitative measurement of the extent of membrane fluidity. Question Type: Essay Chapter: 7 Blooms: Applying, Analyzing Difficulty: Moderate 14\. Describe how you would prepare liposomes from a biological membrane. Ans: The first step would be to treat the biological membrane with an organic solvent such as a mixture of chloroform and methanol. This would dissolve phospholipids and cholesterol, but not proteins or carbohydrates. Once the dissolved lipids were separated from the proteins and carbohydrates, you would evaporate the solvent. The final step would be to disperse the residue (which consists of phospholipids and cholesterol) in water to form liposomes. Question Type: Essay Chapter: 7 Blooms: Applying, Creating Difficulty: Moderate *Section 7.2* 15\. What type of simple-pass membrane protein would contain a hydrophobic membrane-spanning -helix? a\. transmembrane protein b\. integral membrane protein c\. peripheral protein d\. transmembrane protein and integral membrane protein Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Difficult 16\. Which of the following is TRUE regarding lipid-anchored membrane proteins? a\. They are only present on the exoplasmic leaflet of the cell. b\. They are only present on the endoplasmic leaflet of the cell. c\. They are only present on the cytosolic leaflet of the cell. d\. They can be present on either the cytosolic or exoplasmic leaflet of the cell. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 18\. Proteins can be attached to the phospholipid bilayer plasma membrane by covalently linked hydrocarbon groups. Which of the following mechanisms are employed in this anchoring? Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 19\. In immunofluorescence studies you always see the small G-protein Ras in a specific region of the cell and, given its protein sequence along with many other proteins localized to this area, you hypothesize that their C-terminal Cys-Ala-Ala-X (X can be any amino acid) motifs may be responsible for targeting these proteins to this subcellular region. To test this hypothesis, you genetically engineer the sequence encoding this motif onto a cDNA encoding green fluorescent protein. When immunofluorescence is used, where specifically would you expect to see GFP localized in the cell? a\. in the nucleus b\. in the cytoplasm c\. in the Golgi d\. at the plasma membrane Question Type: Multiple Choice Chapter: 7 Blooms: Applying, Analyzing Difficulty: Moderate 20\. Human alkaline phosphatase protein is attached to the plasma membrane by a GPI anchor. In an experiment you treat cells with each of the following enzymes and find one of them inhibits the activity of the protein because it releases it into the extracellular matrix. Which specific enzyme led you to conclude that this anchor on alkaline phosphatase was both necessary and sufficient for binding the protein to the membrane where it can perform its normal activity? a\. glycosyltransferases b\. phospholipase C c\. flippases d\. none of the above Ans: b Question Type: Multiple Choice Chapter: 7 Blooms: Applying, Analyzing Difficulty: Difficult 21\. Peripheral membrane proteins a\. contain many hydrophobic amino acid residues. b\. contain membrane spanning domains. c\. have covalently attached lipid or fatty acid anchors. d\. may noncovalently interact with phospholipid heads. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 22\. The \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are transmembrane proteins. a\. lipid-anchored membrane proteins b\. integral membrane proteins c\. peripheral membrane proteins d\. extracellular matrix proteins Ans: b Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 23\. Porins a\. are peripheral membrane proteins. b\. contain no hydrophobic amino acid residues. c\. have many hydrophobic α-helical regions. d\. allow small hydrophilic molecules to pass through a membrane. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 24\. Glycolipids and glycoproteins are especially abundant in the a\. nucleus. b\. mitochondrial inner membrane. c\. cytosol. d\. plasma membrane. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 25\. Movement of phospholipids from one leaflet to the other a\. occurs routinely. b\. requires cholesterol. c\. requires flippases. d\. is impossible. Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 26\. What are the primary functions of the plasma membrane in all cells? Ans: In both bacteria and higher eukaryotic cells, the plasma membrane provides similar functions. These include regulation of nutrient transport into the cell and release of metabolic waste to the extracellular environment. By allowing certain material to pass in and out of the cell, and preventing other material from passing in and out of the cell, the plasma membrane acts to set up a molecular environment inside the cell that is different from the extracellular environment. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 27\. When examined by fluorescence recovery after photobleaching (FRAP), certain integral membrane proteins are significantly less mobile than others. What accounts for this reduced mobility? Ans: The decreased mobility of certain integral proteins is due to interactions with the cytoskeleton or the extracellular matrix. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 28\. Describe how charged amino acids guide the assembly of membrane complexes such as the T-cell receptor. Ans: The T-cell receptor is composed of four dimers. Each contains specific charged residues as part of its transmembrane segments. The charged residues of neighboring segments interact with each other electrostatically in such a way that the overall charge of the transmembrane portion of the complex is minimized. These interactions serve to anchor dimers together to form the complex. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Hard *Section 7.3* 29\. Free and unesterified fatty acids bind to one of a number of chaperone proteins in order to be transported in the aqueous environment of the cytosol. Which of the following facilitates this intracellular transport? a\. fatty acid-binding proteins b\. aquaporins c\. flippases d\. fatty acid synthase Ans: a Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 30\. The major site of lipid synthesis in eukaryotic cells is the a\. nucleus. b\. endoplasmic reticulum (ER). c\. peroxisome. d\. mitochondria. Ans: b Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 31\. Phosphate-containing lipids include all of the following except a\. plasmalogen. b\. phospholipids. c\. sphingolipid. d\. triglyceride. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 32\. Cholesterol, bile acids, ergosterol, and stigmasterol share all the following common structural features except a\. a four-ring structure. b\. a hydroxyl group on first ring. c\. a carboxylic acid group. d\. a multiple carbon chain extending off the ring structure. Ans: c Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 33\. The enzyme in cholesterol biosynthesis subject to feedback inhibition is a\. ABCB4. b\. desaturase. c\. fatty acid synthase. d\. HMG CoA reductase. Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy 34\. Cholesterol and phospholipids are transported between organelles by a\. Golgi-dependent mechanisms. b\. incompletely characterized vesicle populations. c\. direct contact between membranes and, to some extent, small, soluble lipid-transfer proteins. d\. b and c Ans: d Question Type: Multiple Choice Chapter: 7 Blooms: Remembering, Understanding Difficulty: Hard 35\. Describe how unesterified fatty acids unlinked to CoA are able to move through the aqueous environment of the cytoplasm. Ans: Fatty acid-binding proteins contain a hydrophobic pocket lined by β sheets. The ability of unesterified fatty acids to fit inside this pocket and interact non-covalently with the surrounding protein facilitates their intracellular movement. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 36\. There are several enzymes involved in cholesterol biosynthetic pathway. Which of these is subject to feedback regulation? How does this enzyme sense cholesterol levels? Ans: HMG-CoA reductase catalyzes the key rate-controlling step in cholesterol biosynthesis, the conversion of HMG CoA to mevalonate. The activity of this enzyme is tightly regulated. The enzyme is an endoplasmic reticulum (ER) membrane protein and has a number of transmembrane segments. Five of the transmembrane segments compose the sterol-binding domain. The sterol-binding domain senses the level of cholesterol in the ER membrane. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Moderate 37\. How are cholesterol and phospholipids transported between organelles? Ans: The final steps in the synthesis of cholesterol and phospholipids take place primarily in the ER. Transport from there to other organelles is by poorly understood mechanisms. The transport is Golgi-independent. It is proposed to be either by membrane-limited vesicles or other protein-lipid complexes, direct contact between membranes, or by transfer via small, soluble lipid-transfer proteins. Some combination of these processes is likely important. Question Type: Essay Chapter: 7 Blooms: Remembering, Understanding Difficulty: Easy