Cell Biology: Cell Membranes and Organelles
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Cell Biology: Cell Membranes and Organelles

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Questions and Answers

What is the primary function of membranes in a cell?

  • Storing genetic information
  • Executing transport, enzyme activity, and cell communication (correct)
  • Supporting the cell's structure
  • Regulating cell growth and division

    • Which type of lipid molecule is most abundant in membranes?

  • Triacylglycerols
  • Phospholipids (correct)
  • Cholesterol
  • Sphingolipids

    • What is the estimated frequency of lateral movement in the plasma membrane?

  • Once per minute
  • 100000 times per second
  • 100000000 times per second (correct)
  • Once per hour

    • What is the primary reason for the fluidity of membranes?

    <p>Non-covalent bonds between lipid molecules</p> Signup and view all the answers

    What is the characteristic of the plasma membrane in terms of its composition?

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

    What is the estimated number of different types of lipids found in membranes?

    <p>500-1000</p> Signup and view all the answers

    What is the primary function of clathrin-positive compartments and vesicles in the cell?

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

    What is the thickness of most membranes in the cell?

    <p>5-10 nm</p> Signup and view all the answers

    What is the characteristic of the movement of lipids in the membrane?

    <p>Rapid lateral movement and slow flip-flop movement</p> Signup and view all the answers

    What is the composition of the membrane in terms of lipids and proteins?

    <p>Approximately 50 lipid molecules per protein</p> Signup and view all the answers

    Which type of molecules can dissolve in the lipid bilayer and pass through the membrane rapidly?

    <p>Hydrophobic molecules</p> Signup and view all the answers

    What is the primary function of the Na+/K+ pump in animal cells?

    <p>To control the osmolarity of the cell</p> Signup and view all the answers

    What is the role of clathrin molecules in the cell?

    <p>To assemble at the membrane and cause it to bend inwards</p> Signup and view all the answers

    What is the function of post-translational modifications of proteins?

    <p>To target proteins to specific compartments in the cell</p> Signup and view all the answers

    What is the primary function of motor proteins in the cell?

    <p>To transport vesicles and organelles around the cell</p> Signup and view all the answers

    What is the function of the nuclear pore complex?

    <p>To import and export macromolecules between the nucleus and cytoplasm</p> Signup and view all the answers

    What is the role of myosin motor proteins in muscle contraction?

    <p>To walk along actin filaments and drag other filaments along</p> Signup and view all the answers

    What is the function of chromatophores in cephalopods?

    <p>To change the colour of the organism</p> Signup and view all the answers

    What is the primary function of the Golgi body in protein synthesis?

    <p>To package proteins for secretion</p> Signup and view all the answers

    What is the function of ubiquitination in protein degradation?

    <p>To mark proteins for degradation in the proteasome</p> Signup and view all the answers

    What is the primary mechanism by which cells regulate their intracellular osmolarity?

    <p>Actively pumping out inorganic ions from the cell</p> Signup and view all the answers

    What is the role of glycosylation in protein targeting?

    <p>Targeting proteins to the plasma membrane</p> Signup and view all the answers

    What is the primary function of the nuclear envelope?

    <p>To regulate protein import and export</p> Signup and view all the answers

    What is the primary function of myosin motor proteins in cells?

    <p>To transport vesicles along actin filaments</p> Signup and view all the answers

    What is the primary mechanism of protein transport through the nuclear pore complex?

    <p>Recognition of nuclear localisation signals</p> Signup and view all the answers

    What is the primary function of the Na+/K+ pump in animal cells?

    <p>To maintain a stable concentration of inorganic ions</p> Signup and view all the answers

    What is the primary mechanism of vesicle transport in cells?

    <p>Vesicular transport</p> Signup and view all the answers

    What is the primary function of the Golgi body in protein synthesis?

    <p>To package and modify proteins for transport</p> Signup and view all the answers

    What is the primary mechanism of osmosis in cells?

    <p>Water moving into the cell</p> Signup and view all the answers

    What is the primary function of phosphorylation in protein targeting?

    <p>Regulating protein-protein interactions</p> Signup and view all the answers

    What is the primary function of membranes in terms of cell communication?

    <p>Cell recognition and signaling</p> Signup and view all the answers

    What is the characteristic of membrane-bound ribosomes in terms of protein synthesis?

    <p>Synthesizing proteins for secretion</p> Signup and view all the answers

    What is the key difference between bacterial membranes and animal cell membranes?

    <p>Bacterial membranes have a different composition than animal cell membranes</p> Signup and view all the answers

    What is the primary function of phospholipids in membranes?

    <p>To form the lipid bilayer structure</p> Signup and view all the answers

    What is the result of the asymmetrical structure of the plasma membrane?

    <p>Selectively permeable membrane</p> Signup and view all the answers

    What is the role of non-covalent bonds in maintaining membrane fluidity?

    <p>To regulate the movement of lipids in the membrane</p> Signup and view all the answers

    What is the characteristic of the movement of lipids in the plasma membrane?

    <p>Lateral movement occurs rapidly, while flip-flop movement occurs slowly</p> Signup and view all the answers

    What is the function of enveloped viruses in terms of membrane composition?

    <p>To derive their membrane composition from the host cell</p> Signup and view all the answers

    What is the result of the variation in head groups, hydrocarbon chain lengths, and saturation states of phospholipids?

    <p>Increased diversity of membrane lipids</p> Signup and view all the answers

    What is the characteristic of the composition of membranes in terms of lipids and proteins?

    <p>Lipids are much smaller than proteins</p> Signup and view all the answers

    Study Notes

    Cell Membranes and Compartments

    • Cell membranes are sheet-like structures, 2 molecules thick, forming closed boundaries, typically 5-10 nm thick.
    • Membranes are composed of lipids and proteins, with approximately 50 lipid molecules per protein in a plasma membrane.
    • Phospholipids are the most abundant membrane lipids, with 500-1000 different types identified, varying in head groups, hydrocarbon chain lengths, and saturation states.

    Membrane Structure and Function

    • The plasma membrane is asymmetrical, with lateral movement occurring around 100 million times per second and flip-flop movement less than once per month.
    • Membrane fluidity depends on non-covalent bonds, membrane composition, and temperature.
    • The plasma membrane regulates molecular traffic, allowing hydrophobic molecules like hydrocarbons to dissolve in the lipid bilayer and pass through rapidly.

    Cellular Compartmentalization

    • Cells are compartmentalized, with separate regions for different functions, and busy with various activities.
    • The amino acid sequence of a protein contains instructions for its cellular location.
    • Post-translational modifications like glycosylation, phosphorylation, and ubiquitination affect protein location and function.

    Protein Transport

    • There are three main ways to transport proteins: gated transport (nuclear pore), transmembrane transport (mitochondria), and vesicular transport (motor proteins).
    • The nuclear envelope consists of two concentric membranes with nuclear pores, importing proteins and exporting mRNA.

    Motor Proteins and Vesicle Transport

    • Three types of motor proteins (myosin, kinesin, and dynein) transport vesicles along actin microfilaments and microtubules, requiring ATP energy.
    • Motor proteins also play a role in muscle contraction and cell movement.
    • In some organisms, motor proteins transport pigment molecules along microtubules to change color and adapt to environmental conditions.

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    Test your knowledge of cell membranes, organelles, and their functions. Learn about the different types of membranes, organelles, and their roles in cellular processes.

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