Animal Cell Structure and Function
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Questions and Answers

What is the approximate thickness of the plasma membrane in animal cells?

  • 75-100 nm (correct)
  • 30-40 nm
  • 15 A
  • 45 A
  • According to the fluid mosaic model, how are the phospholipids arranged in the plasma membrane?

  • Hydrophilic polar heads are arranged in the middle and hydrophobic non-polar tails point inwards.
  • Hydrophilic polar heads are evenly distributed throughout the membrane.
  • Hydrophilic polar heads are towards the inner surface and hydrophobic non-polar tails point outwards.
  • Hydrophilic polar heads are towards the outer surface and hydrophobic non-polar tails point inwards. (correct)
  • Which type of proteins in the plasma membrane are either embedded in the lipid layer or superficially attached?

  • Cholesterol molecules
  • Extrinsic (peripheral) proteins
  • Integral (intrinsic) proteins (correct)
  • Glycoproteins
  • What percentage of proteins make up the plasma membrane in animal cells?

    <p>60-70%</p> Signup and view all the answers

    What do carbohydrates form on the outer surface of the plasma membrane in animal cells?

    <p>Glycolipids and glycoproteins</p> Signup and view all the answers

    What prevents some small molecules from crossing the membrane and keeps the membrane fluid and flexible?

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

    What characteristic of phospholipids helps maintain fluidity in the cell membrane at lower temperatures?

    <p>Unsaturated fatty acids</p> Signup and view all the answers

    What functions as a buffer, preventing lower temperatures from inhibiting fluidity and preventing higher temperatures from increasing fluidity too much?

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

    What type of transport involves substance moving from its high concentration towards its lower concentration?

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

    In osmosis, where do solvent molecules migrate across a semi-permeable membrane?

    <p>From a region of low solute concentration to a region of high solute concentration</p> Signup and view all the answers

    Study Notes

    Plasma Membrane Structure and Function

    • The plasma membrane in animal cells has an approximate thickness of 5-10 nanometers.
    • According to the fluid mosaic model, phospholipids in the plasma membrane are arranged in a bilayer, with their hydrophobic tails facing inward and hydrophilic heads facing outward.
    • Integral proteins are embedded in the lipid layer, while peripheral proteins are superficially attached to the plasma membrane.
    • Proteins make up approximately 50% of the plasma membrane in animal cells.

    Carbohydrates and Fluidity

    • Carbohydrates form a glycocalyx on the outer surface of the plasma membrane in animal cells.
    • Unsaturation of phospholipid tails prevents some small molecules from crossing the membrane and keeps the membrane fluid and flexible.
    • The unsaturated tails of phospholipids help maintain fluidity in the cell membrane at lower temperatures by allowing them to remain flexible and not solidify.

    Cholesterol and Temperature Regulation

    • Cholesterol functions as a buffer, preventing lower temperatures from inhibiting fluidity and preventing higher temperatures from increasing fluidity too much.

    Transport and Osmosis

    • Passive transport involves substances moving from their high concentration towards their lower concentration.
    • In osmosis, solvent molecules migrate across a semi-permeable membrane from an area of high concentration to an area of low concentration.

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    Description

    Test your knowledge about the structure and composition of animal cells, including the plasma membrane, cytoplasm, and nucleus. Learn about the functions and characteristics of these key components.

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