Mastering Biology Chapter 7 Flashcards
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Questions and Answers

Which of the following types of molecules are the major structural components of the cell membrane?

  • Carbohydrates
  • Phospholipids and proteins (correct)
  • Nucleotides
  • Steroids

    • What is represented by Figure 7.1 that corresponds to peripheral proteins?

    D

    What is represented by Figure 7.1 that corresponds to cholesterol?

    E

    What does A in Figure 7.1 correspond to?

    <p>Fiber of the extracellular matrix</p> Signup and view all the answers

    What does C in Figure 7.1 represent?

    <p>Microfilament of the cytoskeleton</p> Signup and view all the answers

    What does B in Figure 7.1 correspond to?

    <p>Glycolipid</p> Signup and view all the answers

    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:

    <p>the hydrophobic interactions that hold the membrane together are weakest at this point.</p> Signup and view all the answers

    The presence of cholesterol in the plasma membranes of some animals enables the membrane to:

    <p>stay fluid more easily when cell temperature drops.</p> Signup and view all the answers

    According to the fluid mosaic model of cell membranes, which is a true statement about membrane phospholipids?

    <p>They can move laterally along the plane of the membrane.</p> Signup and view all the answers

    How do the membranes of winter wheat remain fluid in extremely cold temperatures?

    <p>by increasing the percentage of unsaturated phospholipids in the membrane.</p> Signup and view all the answers

    In order for a protein to be an integral membrane protein, it would have to be:

    <p>amphipathic.</p> Signup and view all the answers

    When a membrane is freeze-fractured, what are the bumps seen on the fractured surface of the membrane?

    <p>Integral proteins.</p> Signup and view all the answers

    Why do unsaturated fatty acids help keep membranes more fluid at lower temperatures?

    <p>The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart.</p> Signup and view all the answers

    Which of the following is true of integral membrane proteins?

    <p>They are usually transmembrane proteins.</p> Signup and view all the answers

    What is the most important function for the glycoproteins and glycolipids of animal cell membranes?

    <p>A cell's ability to distinguish one type of neighboring cell from another.</p> Signup and view all the answers

    An animal cell lacking oligosaccharides on its plasma membrane would likely be impaired in which function?

    <p>Cell-cell recognition.</p> Signup and view all the answers

    In the years since the proposal of the fluid mosaic model, what observation has been added to the model?

    <p>The concentration of protein molecules is now known to be much higher.</p> Signup and view all the answers

    Which of the following span the phospholipid bilayer, usually multiple times?

    <p>Transmembrane proteins.</p> Signup and view all the answers

    Which of these are not embedded in the lipid bilayer at all?

    <p>Peripheral proteins.</p> Signup and view all the answers

    Which of these are attached to the extracellular matrix?

    <p>Integrins.</p> Signup and view all the answers

    Which of these often serve as receptors or cell recognition molecules on cell surfaces?

    <p>Glycoproteins.</p> Signup and view all the answers

    The formulation of a model for a structure or for a process serves which of the following purposes?

    <p>It functions as a testable hypothesis.</p> Signup and view all the answers

    Cell membranes are asymmetrical. What is the most likely explanation?

    <p>Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi.</p> Signup and view all the answers

    What is true of the evolution of cell membranes?

    <p>As populations of organisms evolve, different properties of their cell membranes are selected for or against.</p> Signup and view all the answers

    Why are lipids and proteins free to move laterally in membranes?

    <p>Hydrophilic portions of the lipids are in the interior of the membrane.</p> Signup and view all the answers

    What kinds of molecules pass through a cell membrane most easily?

    <p>Small and hydrophobic.</p> Signup and view all the answers

    Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

    <p>It exhibits a specificity for a particular type of molecule.</p> Signup and view all the answers

    After a membrane freezes and then thaws, why does it often become leaky to solutes?

    <p>The integrity of the lipid bilayer is broken when the membrane freezes.</p> Signup and view all the answers

    Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

    <p>CO2.</p> Signup and view all the answers

    Which of the following statements is correct about diffusion?

    <p>It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.</p> Signup and view all the answers

    Why does water pass quickly through cell membranes?

    <p>It moves through aquaporins in the membrane.</p> Signup and view all the answers

    Chloride ion channels in cell membranes are classified as what type of molecules?

    <p>Hydrophilic proteins.</p> Signup and view all the answers

    What problem can arise for someone with nonfunctional chloride channels in cystic fibrosis?

    <p>Buildup of excessive secretions in organs such as lungs.</p> Signup and view all the answers

    What aspect of cystic fibrosis would affect the fertility of a young male child?

    <p>Incorrect concentrations of ions in semen.</p> Signup and view all the answers

    Initially, in terms of tonicity, the solution in side A with respect to that in side B is?

    <p>Isotonic.</p> Signup and view all the answers

    After the system reaches equilibrium, what changes are observed?

    <p>The water level is higher in side A than in side B.</p> Signup and view all the answers

    What is the most probable result of transfusing distilled water into a patient who has lost a lot of blood?

    <p>The patient’s red blood cells will swell because the blood fluid is hypotonic compared to the cells.</p> Signup and view all the answers

    What can be deduced about the cells of celery stalks that become stiff in fresh water?

    <p>They are hypertonic to fresh water but hypotonic to the salt solution.</p> Signup and view all the answers

    A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a solution of the same concentration. The tonicity of the external solution is described as?

    <p>Isotonic.</p> Signup and view all the answers

    At the beginning of the experiment in Figure 7.3, side A is described as?

    <p>Hypotonic to side B.</p> Signup and view all the answers

    If you examine side A after 3 days, what should you find?

    <p>A decrease in the concentration of NaCl and a decrease in the water level.</p> Signup and view all the answers

    Which statement correctly describes the normal tonicity conditions for typical plant and animal cells?

    <p>The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.</p> Signup and view all the answers

    In Figure 7.4, which line represents the bag that contained a solution isotonic to the 0.6 molar solution at the beginning of the experiment?

    <p>C.</p> Signup and view all the answers

    In Figure 7.4, which line represents the bag with the highest initial concentration of sucrose?

    <p>A.</p> Signup and view all the answers

    In Figure 7.4, which line or lines represent(s) bags that contain a solution that is hypertonic at the end of 60 minutes?

    <p>B.</p> Signup and view all the answers

    Which factor determines whether a molecule enters the cytoplasm of specific target cells when designing a new drug?

    <p>Similarity of the drug molecule to other molecules transported by the target cells.</p> Signup and view all the answers

    In which of the following would there be the greatest need for osmoregulation?

    <p>A terrestrial animal such as a snake.</p> Signup and view all the answers

    When a plant cell is submerged in a very hypotonic solution, what is likely to occur?

    <p>The cell will become turgid.</p> Signup and view all the answers

    Which membrane activities require energy from ATP hydrolysis?

    <p>Na+ ions moving out of the cell.</p> Signup and view all the answers

    What are the membrane structures that function in active transport?

    <p>Integral proteins.</p> Signup and view all the answers

    What transport mechanism is most probably functioning in the intestinal cells to rapidly move glucose?

    <p>Facilitated diffusion.</p> Signup and view all the answers

    What is the voltage across a membrane called?

    <p>Membrane potential.</p> Signup and view all the answers

    In most cells, electrochemical gradients of many ions across the plasma membrane are likely maintained by?

    <p>Cotransport proteins.</p> Signup and view all the answers

    Why is the sodium-potassium pump considered an electrogenic pump?

    <p>It contributes to the membrane potential.</p> Signup and view all the answers

    If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions, what is most likely true?

    <p>A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.</p> Signup and view all the answers

    The movement of potassium into an animal cell requires?

    <p>An energy source such as ATP or a proton gradient.</p> Signup and view all the answers

    Ions diffuse across membranes down their:

    <p>Electrochemical gradients.</p> Signup and view all the answers

    What mechanisms do plants use to load sucrose into specialized cells in the veins of leaves?

    <p>An electrogenic pump, a proton pump, a cotransport protein.</p> Signup and view all the answers

    Where will the ATP binding site be on a sodium-potassium pump protein first synthesized in the rough ER?

    <p>It will be on the cytoplasmic side of the ER.</p> Signup and view all the answers

    What does the presence of proton pumps in various kingdoms suggest?

    <p>Cells with proton pumps were maintained in each kingdom by natural selection.</p> Signup and view all the answers

    Which development has improved the outcome of serious viral diseases resulting in dehydration?

    <p>Hydrating drinks that include high concentrations of salts and glucose.</p> Signup and view all the answers

    What process would an organism with a cell wall find most difficult to execute?

    <p>Phagocytosis.</p> Signup and view all the answers

    Through what process do white blood cells engulf bacteria?

    <p>Phagocytosis.</p> Signup and view all the answers

    Familial hypercholesterolemia is characterized by?

    <p>Defective LDL receptors on the cell membranes.</p> Signup and view all the answers

    What is the difference between pinocytosis and receptor-mediated endocytosis?

    <p>Pinocytosis brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as well.</p> Signup and view all the answers

    In receptor-mediated endocytosis, where do receptor molecules end up after endocytosis?

    <p>On the inside surface of the vesicle.</p> Signup and view all the answers

    How do the membranes of a eukaryotic cell vary?

    <p>Certain proteins are unique to each membrane.</p> Signup and view all the answers

    According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly?

    <p>Embedded in a lipid bilayer.</p> Signup and view all the answers

    Which factor would tend to increase membrane fluidity?

    <p>A greater proportion of unsaturated phospholipids.</p> Signup and view all the answers

    Which of the following processes includes all others?

    <p>Passive transport.</p> Signup and view all the answers

    Study Notes

    Cell Membrane Components

    • Major structural components: phospholipids and proteins
    • Integral membrane proteins usually span the bilayer multiple times
    • Peripheral proteins are not embedded within the lipid bilayer

    Membrane Structure and Properties

    • Cholesterol maintains membrane fluidity, especially at lower temperatures
    • Unsaturated fatty acids keep membranes fluid in cold environments due to kinks in their tails
    • Membranes are asymmetrical because proteins are allocated as they are packaged in the ER and Golgi

    Membrane Functionality

    • Cell membranes permit the lateral movement of phospholipids
    • Glycoproteins and glycolipids are essential for cell recognition and signaling
    • Na+ ions require ATP for active transport out of cells

    Transport Mechanisms

    • Small, hydrophobic molecules pass membranes easily
    • Facilitated diffusion allows rapid transport of glucose in intestinal cells
    • Aquaporins enable quick water transport across membranes

    Tonicity and Osmoregulation

    • Isotonic solutions maintain balance in cells, while hypotonic solutions can cause swelling
    • Plant cells become turgid in hypotonic solutions, while animal cells can burst
    • Osmoregulation is crucial for terrestrial animals to manage water balance

    Ion Channels and Pumps

    • Electrochemical gradients across membranes are maintained by pumps like the sodium-potassium pump
    • Cotransport proteins facilitate the movement of ions and molecules across membranes
    • Proton pumps play a key role in various cellular processes across all kingdoms

    Disease Implications

    • Cystic fibrosis results from defective chloride channels, leading to secretions buildup
    • Familial hypercholesterolemia involves defective LDL receptors affecting cholesterol uptake

    Endocytosis Processes

    • Phagocytosis is utilized by white blood cells to engulf bacteria
    • Pinocytosis differs from receptor-mediated endocytosis by only bringing in fluids instead of specific molecules

    Membrane Fluidity Factors

    • Greater proportions of unsaturated phospholipids increase membrane fluidity
    • Membrane structures are influenced by the unique proteins present in specific membranes

    Membrane Model

    • The fluid mosaic model describes proteins embedded within a lipid bilayer
    • New observations suggest that the concentration of protein molecules in membranes is generally higher than previously thought

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    Dive into the vital concepts of cell membranes with these flashcards from Chapter 7 of Mastering Biology. Test your knowledge on key components such as phospholipids, proteins, and the extracellular matrix. Perfect for reinforcing your understanding of cellular structures.

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