Cell Membrane and Organelles Overview
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Cell Membrane and Organelles Overview

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Questions and Answers

What are membranous organelles?

Permanent structures in nucleated cells that contain enzymes and are enclosed in membranes.

Which of the following are examples of membranous organelles? (Select all that apply)

  • Mitochondria (correct)
  • Golgi complex (correct)
  • Cell membrane (correct)
  • Cytoplasm
  • What are intrinsic proteins?

    Proteins made of small or large protein molecules firmly embedded in the lipid bilayer.

    Extrinsic proteins can be easily removed from the cell membrane without disrupting the lipid bilayer.

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

    What is the cell coat (glycocalyx)?

    <p>A layer of glycoprotein or glycolipid on the external surface of the cell membrane.</p> Signup and view all the answers

    What does the basal surface of epithelial cells contain?

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

    What are the main classes of lipids in the cell membrane?

    <p>Phospholipids, glycolipids, and cholesterol.</p> Signup and view all the answers

    The protruding structures on the apical surface of the epithelium that increase absorptive surface area are called __________.

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

    Myelin sheath surrounds nerve fibers and conducts nerve impulses.

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

    What happens during simple transport (diffusion) across the cell membrane?

    <p>Gases and water can pass into the cell.</p> Signup and view all the answers

    What role do cilia play on the surface of respiratory tract epithelium?

    <p>They push particles or fluids in one direction.</p> Signup and view all the answers

    Study Notes

    Membranous Organelles

    • Permanent structures found in nucleated cells
    • Contain enzymes
    • Enclosed within membranes
    • Participate in cellular metabolism
    • Examples: cell membrane, mitochondria, Golgi complex, lysosomes, peroxisomes, endoplasmic reticulum (rough and smooth), and coated vesicles

    Cell Membrane Proteins

    • Arranged as extrinsic or intrinsic proteins

    Extrinsic Proteins (Peripheral Proteins)

    • Loosely attached to the cell membrane's surface
    • Easily removed without disrupting the lipid bilayer

    Intrinsic Proteins (Integral Proteins)

    • Firmly embedded in the lipid bilayer
    • Some extend across the entire width of the membrane, protruding from both surfaces
    • Transmembrane proteins are involved in transporting molecules in and out of the cell
    • Can be "one-pass" or "multi-pass" proteins
    • Have hydrophilic regions at outer and inner membrane surfaces
    • Have hydrophobic regions in the center of the lipid bilayer

    The Cell Coat (Glycocalyx)

    • Layer of glycoprotein or glycolipid on the cell membrane's external surface
    • Functions: immunological specificity, contains blood group antigens, receptor sites, holds cells together, forms part of basement membrane for epithelial tissues, protective mechanical barrier

    Cell Surface Specializations

    Lateral Surfaces

    • Junctional complexes and interdigitations interlock adjacent epithelial cells

    Basal Surfaces

    • Flagella propel sperm cells

    The Cell Membrane (Plasmalemma)

    • Site: surrounds the cell
    • Structure:
      • Thin and difficult to see by light microscopy
      • Appears dark brown when stained with silver
      • Electron micrograph shows two dark layers separated by a light layer (trilaminar membrane)
    • Chemical composition: lipids, proteins, and carbohydrates

    The Lipid Component

    • Major classes: phospholipids, glycolipids, and cholesterol
    • Phospholipids form a double layer
      • Polar (hydrophilic) heads directed outwards, appear dark in electron microscopy
      • Non-polar (hydrophobic) tails directed inwards, appear light in electron microscopy

    Apical Surface

    • Microvilli are finger-like projections that increase absorptive surface area in epithelia
    • Cilia move particles or fluids in one direction on respiratory tract epithelium

    Around the Surface

    • Myelin sheath surrounds nerve fibers to insulate nerve impulses

    Cell Membrane Functions

    • Simple transport (diffusion) allows gases and water to pass through the membrane by diffusion
    • Active transport requires energy for large molecules like sugar to enter the cell

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    Description

    This quiz covers the crucial concepts of membranous organelles and cell membrane proteins, including intrinsic and extrinsic proteins. Explore the roles and structures of various organelles like mitochondria and lysosomes, as well as the unique characteristics of cell membrane proteins. Perfect for students studying cellular biology.

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