Midterm Review Packet

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When biologists wish to study the internal ultrastructure of cells, they can achieve the finest resolution by using
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A transmission electronic microscope
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The advantage of light microscopy over electron microscopy is that light microscopy allows one to view dynamic processes in living cells
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Light microscopy allows one to view dynamic processes in living cells
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A primary objective of cell fractionation is to
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separate the major organelles so that their particular functions can be determined
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In the fractionation of homogenized cells using centrifugation, the primary factor that determines whether a specific cellular component ends up in the supernatant or the pellet is
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the size and weight of the component
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Which of the following correctly lists the order in which cellular components will be found in the pellet when homogenized cells are treated with increasingly rapid spins in a centrifuge?
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Nucleus, mitochondria, ribosomes
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Green fluorescent protein (GFP) can be used to fluorescently label a specific protein in cells by genetically engineering cells to synthesize the target protein fused to GFP. What is the advantage of using GFP fusions to visualize specific proteins, instead of staining cells with fluorescently labeled probes that bind to the target protein
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GFP fusions enable one to track changes in the location of the protein in living cells; staining usually requires preserved cells
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What is the reason that a modern electron microscope (TEM) can resolve biological images to the sub nanometer level, as opposed to the tens of nanometers achievable for the best super-resolution light microscope?
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Electron beams have much shorter wavelengths than visible light
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What technique would be most appropriate to use to observe the movements of condensed chromosomes during cell division?
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Standard light microscopy
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All of the following (DNA, cell wall, plasma membrane, ribosomes, ER) are part of a prokaryotic cell except
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endoplasmic rediculum
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The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
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Plant cells contain a large vacuole that reduces the volume of the cytoplasm
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A mycoplasma is an organism with a diameter between 0.1 and 1.0 ”m. What does the organism’s size tell you about how it might be classified
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It could be a very small bacterium
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Which of the following is a major cause of the size limits for certain types of cells
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The need for sufficient surface area to support the cell’s metabolic needs
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Which of the following statements concerning cells of bacteria and archaea is correct?
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DNA is present in both archaea and bacteria
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The evolution of eukaryotic cells most likely involved
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endosymbiosis of an aerobic bacterium in a larger host cell-the endosymbiont evolved into mitochondria
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Prokaryotes are classified as belonging to two different domains. What are the domains?
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Bacteria and Archaea
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If radioactive deoxythymidine triphosphate (dTTP) is added to a culture of rapidly growing bacterial cells, where in the cell would you expect to find the greatest concentration of radioactivity?
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Nucleoid
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Which organelle or structure is absent in plant cells?
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Centrosomes
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Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
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Proteins
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The nuclear lamina is an array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you expect to be the most likely immediate consequence?
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A change in the shape of the nucleus
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Recent evidence shows that when chromosomes de-condense during interphase, their DNA molecules do not intermingle. Instead, they occupy distinct territories within the nucleus. Considering the structure and location of the following structures, which is most likely to be involved in chromosome location?
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The nuclear matrix
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A cell with a predominance of free ribosomes is most likely
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Producing primarily cytoplasmic proteins
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Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
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Smooth endoplasmic reticulum
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Which structure is the site of synthesis of proteins that may be exported from the cell?
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Rough Endoplasmic Reticulum
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The Golgi apparatus has a polarity or sidedness to its structure and function. Which of the following statements correctly describes this polarity?
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(Transport Vesicles; Proteins in the membrane; Lipids in the membrane; Soluble proteins in the cisternae) All of the above correctly describe polar characteristics of the Golgi function
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The fact that the outer membrane of the nuclear envelope has bound ribosomes allows one to most reliably conclude that
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At least some of the proteins that function in the nuclear envelope are made by the ribosomes on the nuclear envelop
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The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by
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The function of the Golgi apparatus in sorting and directing membrane components
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Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. Which of the following organelles contains these hydrolytic enzymes in animal cells?
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Lysosome
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Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
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Proteins that are secreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane
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Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large, complex, and undigested lipids. Which cellular organelle must be involved in this collection?
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The lysosome
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The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?
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Smooth Endoplasmic Reticulum
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Which of the following contains hydrolytic enzymes?
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Lysosome
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Which organelle often takes up much of the volume of a plant cell?
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Vacuole
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Which organelle is the primary site of ATP synthesis in eukaryotic cells?
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Mitochondrion
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Which plant cell organelle contains its own DNA and ribosomes?
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Mitochondrion
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Which animal cell organelle contains enzymes that transfer hydrogen from various substrates to oxygen?
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Peroxisome
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Thylakoids, DNA and ribosomes are all components found in
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Chloroplasts
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In a plant cell, DNA may be found
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in the nucleus, mitochondria, and chloroplasts
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The chemical reactions involved in respiration are virtually identical between prokaryotic and eukaryotic cells. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where is most ATP synthesis likely to occur in prokaryotic cells?
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On the plasma membrane
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One of the key innovations in the evolution of eukaryotes from a prokaryotic ancestor is the endomembrane system. What eukaryotic organelles or features might have evolved as a part of, or as an elaboration of, the endomembrane system?
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Nuclear envelope
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A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
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nearly any eukaryotic organism
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Which type of organelle is found in plant cells but not in animal cells?
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Plastids
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Why isn’t the mitochondrion classified as part of the endomembrane system?
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Its structure is not derived from the ER or Golgi Complex.
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In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and
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Transfer the hydrogen to oxygen molecules to generate hydrogen peroxide
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How does the cell multiply its peroxisomes?
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They split in two after they become sufficiently large.
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Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?
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Cytoskeletal structures
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Movement of vesicles within the cell depends on what cellular structures?
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Microtubules and motor proteins
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The smallest cell structure that would most likely be visible with a standard (not super-resolution) research grade- light microscope is
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A mitochondrion
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Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules?
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Both flagella and motile cilia
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Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to
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separate chromosomes during cell division
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The differences among the three categories of cytoskeletal elements outlined in the table above would suggest that each of the following has specialized roles. Which of the following is a correct match?
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Microtubules and chromosome movement
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Centrioles, cilia, flagella, and basal bodies have remarkably similar structural elements and arrangements. Which of the following hypotheses is most plausible in light of such structural similarities?
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Cilia and flagella arise from the centrioles
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If an individual has abnormal microtubules, due to a hereditary condition, in which organs or tissues would you expect dysfunction?
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Sperm, larynx, and trachea: cells and tissues that contain flagella or cilia
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Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to
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move vesicles around the cell
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Which of the following statements about the cytoskeleton is true?
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Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
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Cells require which of the following to form cilia or flagella?
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Tubulin
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What do the cell walls of plants and the extracellular matrix of animal cells have in common?
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They have functional connections with the cytoskeleton inside the cell
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The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
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They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell
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When a potassium ion (K+) moves from the soil into the vacuole of a cell on the surface of a root, it must pass through several cellular cellular structures. Which of the following correctly describes the order in which these structures will be encountered by the ion?
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Primary cell wall→Plasma membrane→Cytoplasm→Vacuole
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A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its
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Golgi apparatus and extracellular matrix
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The extracellular matrix is thought to participate in the regulation of animal cell behaviour by communicating information from the outside to the inside of the cell via which of the following?
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Integrins
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Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?
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Gap junctions
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Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
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Gap junctions
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Which of the following makes it necessary for animal cells, although they have no cell walls, to have intercellular junctions?
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Maintenance of tissue integrity and barriers to fluid leakage requires cells to adhere tightly to one another.
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Recent evidence shows that signals from the extracellular matrix (ECM) can regulate the expression of genes in the cell nucleus. A likely mechanism is that
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mechanical signals of the ECM can alter the cytoskeleton, which can alter intra cellular signaling.
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Signals from the ECM to the cytoskeleton may be transmitted by
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Integrins
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ECM proteins are made by ribosomes in which part of a eukaryotic cell?
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Rough Endoplasmic Reticulum
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What types of proteins are not synthesized in the rough endoplasmic reticulum?
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Mitochondrial proteins
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Which of the trees in this figure groups the domains according to similarities in cellular size and architecture?
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Bacteria Archaea Eukarya / / / / / / V / / / / V / /
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A biologist wants specifically to examine the surfaces of different types of cells in kidney tubules of small mammals. The cells in question can be distinguished by external shape, size, and 3-D characteristics. Which of the following would be the optimum method for his/her study?
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Scanning electron microscopy
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A newspaper ad for a local toy store indicates that a very inexpensive microscope available for a small child is able to magnify specimens nearly as much as the much more costly microscope available in your college lab. What is the primary reason for the price difference?
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The toy microscope magnifies a good deal, but has low resolution and therefore poor quality images.
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A biologist ground up some plant leaf cells and then centrifuged the mixture to fractionate the organelles. Organelles in one of the heavier fractions could produce ATP in the light, whereas organelles in the lighter fraction could produce ATP in the dark. The heavier and lighter fractions are most likely to contain, respectively,
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Chloroplasts and mitochondria
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Which structure is not part of the endomembrane system?
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chloroplast
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Which structure is common to plant and animal cells?
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Mitochondrion
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Which structure-function pair is mismatched?
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microtubule; muscle contraction
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Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the
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mitochondria
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What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?
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ER→Golgi→vesicles that fuse with plasma membrane
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Which cell would be best for studying lysosomes?
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Phagocytic white blood cell
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Who was/were the first to propose that cell membranes are phospholipid bilayers?
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E. Gorter and F. Grendel
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Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At high temperatures, these regions
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are less fluid than the surrounding membrane
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Singer and Nicolson’s fluid mosaic model of the membrane proposed that
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membranes consist of protein molecules embedded in a fluid bilyer of phospholipids
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Which of the following types of molecules are the major structural components of the cell membrane?
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Phospholipids and proteins
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When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that
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the hydrophobic interactions that hold the membrane together are weakest at this point
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According to the fluid mosaic model of the cel membranes, which of the following is a true statement about membrane phospholipids?
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They can move laterally along the plane of the membrane.
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In order for a protein to be an integral membrane protein, it would have to be
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amphipathic, with at least one hydrophobic region
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When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
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integral proteins
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Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
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The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
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Which of the following is true of integral membrane proteins?
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They are usually transmembrane proteins
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The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is
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to mediate cell-to-cell recognition
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An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
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cell-cell recognition
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in the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?
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The concentration of protein molecules is now known to be much higher
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A protein that spans the phospholipid bilayer one or more times is
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a transmembrane protein
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Which of these are not embedded in the hydrophobic portion of the lipid bilayer at all?
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Peripheral proteins
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The cell membranes of Antarctic ice fish might have which of the following adaptations?
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A high percentage of polyunsaturated fatty acids
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In a paramecium, cell surface integral membrane proteins are synthesized
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by ribosomes bound to the rough endoplasmic reticulum
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The formulation of a model for a structure or for a process serves which of the following purposes?
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It functions as a testable hypothesis
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Cell membranes are asymmetrical. Which of the following is the most likely explanation?
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The two sides of a cell membrane face different environments and carry out different functions
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Which of the following is true of the evolution of cell membranes?
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All components of membranes evolve in response to natural selection
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Why are lipids and proteins free to move laterally in membranes?
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There are only weak hydrophobic interactions in the interior of the membrane.
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What kinds of molecules pass through a cell membrane most easily?
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Small and hydrophobic
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Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
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It exhibits a specificity for a particular type of molecule
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Nitrous oxide gas molecules diffusing across a cell’s plasma membrane is an example of
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diffusion across the lipid bilayer
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Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
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CO₂
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Which of the following statements is correct about diffusion?
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It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
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Water passes quickly through cell membranes because
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It moves through aquaporins in the membrane
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Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that
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The freshwater is hypertonic and the salt solution is hypotonic to the cells of the celery stalks
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Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl What will happen if read blood cells are transferred to seawater
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Water will leave the cells, causing them to shrivel and collapse
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Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
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The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution
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In which of the following would there be the greatest need for osmoregulation?
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Cells of a tide pool animal such as an anemone
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When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
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The cell will become turgid
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Which of the following membrane activities require energy from ATP hydrolysis?
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Naâș ions moving out of a mammalian cell bathed in physiological saline
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The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of
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cotransport
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Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly moves large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
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Facilitated diffusion
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What is the voltage across a membrane called?
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Membrane potential
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In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by
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Cotransport proteins
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The sodium-potassium pump is called an electrogenic pump because it
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contributes to the membrane potential
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Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
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A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose
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Ions diffuse across membranes through specific ion channels
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down their electrochemical gradients
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Which of the following would increase the electrochemical gradient across a membrane?
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a proton pump
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The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
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It will be on the cytoplasmic side of the ER
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Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya
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Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life
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Several epidemic microbial disease of earlier centuries incurred because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?
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Hydrating drinks that include high concentrations of salts and glucose
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An organism with a cell wall would most likely be unable to take in materials through
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phagocytosis
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White blood cells engulf bacteria through what process?
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Phagocytosis
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The difference between pinocytosis and receptor-mediated endocytosis is that
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pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity
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In receptor mediated endocytosis, receptor molecules initially projected to the outside of the cell. Where do they end up after endocytosis?
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On the inside surface of the vesicle
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A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
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lysosomes.
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Which component is cholesterol?
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The spherical molecules in between the membrane
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Which component is the bier of the extracellular matrix?
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The large worm-like fibers outside the cell membrane
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Which component is a microfilament of the the cytoskeleton?
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The very thin fibers within the cell
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Which component is a glycolipid?
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The hexagonal protrusions from the cell membrane
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Initially, in terms of tonicity, the solution in side A with respect to that in side B is
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Isotonic
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After the system reached equilibrium, what changes are observed?
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The water level is higher in Side A than Side B.
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At the beginning of the experiment
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Side A is hypotonic to Side B
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Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
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The flat line
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Which line in the graph represents the bag with the highest initial concentration of sucrose?
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The one with sharp increase that levels off
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Which line or lines in the graph represent(s) bag(s) that contain(s) a solution that is hypertonic at 50 minutes?
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The one that constantly increases
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What would be observed by live-cell fluorescence microscopy immediately after HIV entry if the red fluorescent lipid dye-labelled HIV membrane fuses with the target cell plasma membrane?
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A spot of red fluorescence will be visible on the infected cell’s plasma membrane, marking the site fo membrane fusion and HIV entry
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What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then fuses with the endocytotic vesicle membrane?
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The red fluorescent dye-labeled lipids will appear in the infected cell’s interior
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Using live-cell fluorescence microscopy, researchers observed that a red fluorescer spot moved from the plasma membrane into the interior of target cells when red fluorescent dye-labeled HIV was added to the cells. What is the best conclusion from these observations?
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The hypothesis that HIV enters the cell via fusion with the target cell plasma membrane is not supported.
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If HIV first enters the cell in an endocytotic vesicle, instead of directly fusing with the plasma membrane, then
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HIV infection should be hindered by microtubule polymerization inhibitors such as nocodazole
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In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane?
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They are synthesized by ribosomes in the rough ER, and arrive at the plasma membrane in the membrane of secretory vesicles
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Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins?
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Electrogenic ion pumps
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If the sodium ion concentration outside the cell increases, and the CFTR channel is open, in what direction will chloride ions and water move across the cell membrane?
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Both chloride ions and water will move out of the cell
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In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?
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Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume
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A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water-equal to the volume of blood lost-is transferred directly into one of his veins. What will be the most probable result of this transfusion
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The patient’s red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
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You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
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Similarity of the drug molecule to other molecules transported by the target cells
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According to the fluid mosaic model of membrane structures, proteins of the membrane are mostly
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embedded in a lipid bilayer
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Which of the following factors would tend to increase membrane fluidity?
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A greater proportion of unsaturated phospholipids
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Which of the following processes includes all others?
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Passive transport
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Based on the figure above, which of these experimental treatments would increase the rate of sucrose transport into the cell?
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Decreasing extracellular pH

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