Membrane quiz

Fluid mosaic models of membranes

Membrane

  1. What term refers to a property of fatty acid chains of a phospholipid?

    1. hydrophilic  
    2. hydrophobic  
    3. amphipathic  
    4. polar  

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    Long hydrocarbon chains are nonpolar and will not mix with water so are hydrophobic.

  2. What is an integral protein?

    1. a protein embedded in the phospholipid membrane  
    2. a protein attached to the surface of the membrane  
    3. a protein within the cytoplasm  
    4. a protein enclosed in a vesicle  

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    Integral proteins can be transmembrane - going across the membrane to be exposed on both sides - or embedded on one side of the membrane.  If an integral membrane is removed, the membrane will be disrupted.

  3. What is a peripheral protein?

    1. a protein embedded in the phospholipid membrane  
    2. a protein attached to the surface of the membrane  
    3. a protein within the cytoplasm  
    4. a protein enclosed in a vesicle  

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    Peripheral proteins can be removed from the membrane without the disruption of the membrane.

  4. Cells are able to take in droplets of fluid from outside of the cell to form vesicles containing this liquid.  What is the transport mechanism?

    1. exocytosis  
    2. phagocytosis  
    3. pinocytosis  
    4. facilitated diffusion  

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    Pinocytosis is also called cell drinking and is a form of endocytosis.

  5. Which of the following is mainly responsible for maintaining the structure of a cell membrane?

    1. phospholipids  
    2. water  
    3. proteins  
    4. triglycerides  

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    Phospholipids are amphpathic - having both hydrophobic fatty acid chains that repel water and polar heads that are hydrophilic and so attract water.

  6. During exocytosis, a sequence of events occurs.  What is the correct order?
    I. Formation of a vesicle by the Golgi apparatus
    II. Secretion of the vesicle's contents
    III. Fusion of the vesicle with the plasma membrane
    IV. Movement of the vesicle towards the plasma membrane

    1. I, IV, III, II  
    2. II, III, IV, I  
    3. I, II, III, IV  
    4. III, IV, II, I   

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    Exocytosis is the release of materials from the cells.  Vesicles are made by the Golgi apparatus for exporting from cells.

  7. Which part of a plasma membrane is responsible for preventing the free movement of ions into and out of the cell?

    1. phospholipid bilayer  
    2. channel proteins  
    3. glycoproteins  
    4. cholesterol  

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    Phospholipids have nonpolar tails in the interior of the membrane which would repel the charged ions.  Ions tend to move through channel proteins or by active transport selective pumps.

  8. Which of the following describes facilitated diffusion?
     

    1. The passive movement of a particle through the phospholipid bilayer of the cell membrane.  
    2. The movement of a particle down a concentration gradient helped by active pumping.  
    3. The passive movement of a particle across a cell membrane via a channel protein.  
    4. The movement of a particle up a concentration gradient helped by active pumping.  

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    Facilitated diffusion is passive transport so answers A and D are wrong.

    Active transport works up a concentration gradient so B is wrong.

    Facilitated diffusion involves a channel protein so C is correct.

  9. A membrane protein could have which of the following functions?
     

    1. energy storage  
    2. oxygen uptake  
    3. thermal insulation  
    4. enzymatic action  

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    Enzymatic action by immobilized enzymes are critical functions of membranes, so D is correct.

     

    Energy storage would be by glycogen in animals or starch in plants.

    Oxygen uptake is by hemogolobin which is within red blood cells.

    Thermal insulation is done by layers of fat under the skin not at the membrane level

  10. Which statements are characteristics of diffusion through membranes?
    I. Polysaccharides can be transported.
    II. It can be facilitated by special channels.
    III. It is affected by concentration gradients.

    1. I and II only  
    2. I and III only  
    3. II and III only  
    4. I, II and III  

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    Polysaccharides are too large to pass through membranes by diffusion so this option is incorrect, making A, B and D wrong.

    C is correct as facillated diffusion is mentioned and diffusion works down a concentration gradient.

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