Cell Biology: Prokaryotic vs Eukaryotic Cells
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Questions and Answers

What is the primary structural component of the lipid bilayer?

  • Amphiphilic lipids (correct)
  • Carbohydrates
  • Proteins
  • Nucleic acids

    • Which part of the amphiphilic lipids faces the aqueous solution?

  • Polar head groups (correct)
  • Nonpolar heads
  • Hydrophobic tails
  • Fatty acid chains

    • What characteristic describes the distribution of lipids in the lipid bilayer?

  • Uniform distribution
  • Asymmetric distribution (correct)
  • Symmetric distribution
  • Random distribution

    • What type of lipid is predominant in the outer layer of the membrane?

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

    Which cellular structure is responsible for synthesizing components of the membrane?

    <p>Smooth endoplasmic reticulum</p> Signup and view all the answers

    What is the primary difference in cell structure between prokaryotic and eukaryotic cells?

    <p>Eukaryotic cells possess a nucleus and membrane-bound organelles, while prokaryotic cells do not.</p> Signup and view all the answers

    Which organisms are classified as prokaryotes?

    <p>Bacteria and archaea.</p> Signup and view all the answers

    What best describes the size difference between prokaryotic and eukaryotic cells?

    <p>Eukaryotic cells are approximately 100 to 10,000 times larger than prokaryotic cells.</p> Signup and view all the answers

    Which statement is true regarding unicellular organisms?

    <p>They include both prokaryotes and some eukaryotes like protozoa.</p> Signup and view all the answers

    What distinguishes multicellular organisms from unicellular organisms?

    <p>Multicellular organisms consist of numerous specialized cells organized into tissues.</p> Signup and view all the answers

    What type of molecules are membranes almost impermeable to?

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

    Which component of the membrane helps to increase its fluidity?

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

    What role do cholesterol and glycolipids play in membrane fluidity?

    <p>Stabilize fluidity</p> Signup and view all the answers

    The fluidity of the lipid bilayer is affected by which of the following?

    <p>Both temperature and lipid composition</p> Signup and view all the answers

    Which statement accurately describes the permeability of membranes?

    <p>Almost impermeable to polar molecules and highly permeable to nonpolar molecules and water</p> Signup and view all the answers

    What is one function of the cell membrane related to cell organelles?

    <p>Separates cell compartments within the cytosol.</p> Signup and view all the answers

    How does the cell membrane assist in signal transduction?

    <p>By converting extracellular signals into intracellular reactions.</p> Signup and view all the answers

    What is the primary purpose of the glycocalyx in cells?

    <p>To protect the cell from dehydration</p> Signup and view all the answers

    What is the role of glycoproteins on the cell membrane?

    <p>They enable identification of self vs. non-self cells.</p> Signup and view all the answers

    Which of the following best describes the structure of the glycocalyx?

    <p>A long, branching network of polysaccharides</p> Signup and view all the answers

    What occurs during the electrical excitability function of the cell membrane?

    <p>Generation of an electrochemical gradient across the membrane.</p> Signup and view all the answers

    What are cell junctions primarily formed by?

    <p>Anchor proteins connected to the cytoskeleton.</p> Signup and view all the answers

    How does the glycocalyx contribute to the immune response?

    <p>By enabling immune cells to differentiate between host and foreign cells</p> Signup and view all the answers

    Which of the following is NOT a component of the glycocalyx?

    <p>Nucleic acids</p> Signup and view all the answers

    What role does the glycocalyx play in red blood cells (RBCs)?

    <p>It differentiates blood groups</p> Signup and view all the answers

    What type of diffusion allows individual lipid molecules to move freely within the lipid bilayer?

    <p>Lateral diffusion</p> Signup and view all the answers

    Which mechanism involves the transport of glucose via specific transport proteins?

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

    What is required for transverse diffusion to occur in the membrane?

    <p>Enzymatic support</p> Signup and view all the answers

    Which of the following substances is specifically transported through aquaporin channels in the kidney?

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

    What process is involved in bicarbonate reabsorption in the kidney?

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

    What is the function of ribosomes in eukaryotic cells?

    <p>Protein synthesis</p> Signup and view all the answers

    Which statement correctly describes the DNA structure in prokaryotic cells?

    <p>DNA is circular and located in the cytoplasm</p> Signup and view all the answers

    Which of the following statements is true about mitochondria?

    <p>Only present in eukaryotic cells</p> Signup and view all the answers

    What feature distinguishes the cell wall in prokaryotes from that of eukaryotes?

    <p>Eukaryotic cells have a cell wall only in plants, fungi, and algae</p> Signup and view all the answers

    What is the role of plasmids in prokaryotic cells?

    <p>Circular rings of additional DNA</p> Signup and view all the answers

    What is a key characteristic of integral membrane proteins?

    <p>They completely penetrate the lipid double layer.</p> Signup and view all the answers

    Which of the following best describes peripheral membrane proteins?

    <p>They usually interact through electrostatic affinity or hydrogen bonds.</p> Signup and view all the answers

    What percentage of membrane protein content can be found in the lipid bilayer?

    <p>20-80%</p> Signup and view all the answers

    What is true regarding the binding of integral membrane proteins?

    <p>They strongly bind to the lipid bilayer.</p> Signup and view all the answers

    Which function does NOT typically describe membrane proteins?

    <p>Providing an energy source for the cell.</p> Signup and view all the answers

    Study Notes

    Prokaryotic Cells

    • Single-celled organisms including bacteria
    • Encased by a cell membrane containing cytoplasm

    Eukaryotic Cells

    • Multicellular organisms and some single-celled organisms (e.g., protozoa)
    • Contain a nucleus and other membrane-bound organelles
    • Significantly larger than prokaryotic cells (100 to 10,000 times larger)

    Lipid Bilayer

    • Composed of lipids and proteins
    • Synthesized within the smooth endoplasmic reticulum (SER)

    Lipid Bilayer Structure

    • Consists of amphiphilic lipids like phospholipids and sphingolipids
    • Amphiphilic lipids have a polar head group and a hydrophobic tail
    • Hydrophobic tails face inward, while polar heads form a boundary with water molecules

    Transport Mechanisms

    • Lateral (parallel) diffusion: Individual lipid molecules move freely within the lipid bilayer
    • Transverse diffusion: Very slow and requires enzymatic support
    • Facilitated diffusion: Diffusion of molecules across the cell membrane using carrier proteins, channel proteins, or ions
      • Glucose and fructose transport into cells via GLUT transporters
        • Transport of glucose from the blood into the pancreatic beta cell via GLUT2
      • Water transport via aquaporin channels in principal cells of the kidney
    • Bicarbonate reabsorption in the early proximal convoluted tubule

    Membrane Characteristics

    • Permeability: The cell membrane is permeable to nonpolar molecules and water, but almost impermeable to polar molecules
    • Fluidity: Can change depending on the composition of the bilayer and the temperature
      • Factors increasing fluidity: Unsaturated fatty acids
      • Factors stabilizing fluidity: Cholesterol and glycolipids

    Cell Membrane Functions

    • Separates cell compartments within the cytosol
    • Transports substances into and out of the cell
    • Converts extracellular signals into intracellular reactions
    • Enables cell identification through specific proteins on its surface, mostly glycosylated glycoproteins
    • Generates an electrochemical gradient across the membrane, creating a membrane potential
    • Forms cell junctions using anchor proteins (cell adhesion molecules) connected to the cytoskeleton

    Glycocalyx

    • Loose glycoprotein-polysaccharide layer covering the outside of the cell membrane
    • Contains a long, branching network of polysaccharides, covalently bound to proteins or lipids
    • Functions: protects the cell from dehydration, enables immune cells to differentiate between host cells and foreign organisms, differentiates blood groups

    Overview of Eukaryote and Prokaryote Cell Structure

    Feature Eukaryotes Prokaryotes
    Nucleus Present Absent
    Location of DNA Nucleus Cytoplasm
    DNA Storage Form In several chromosomes (double-stranded), Contains histones Circular bacterial chromosome (termed "chromosome equivalent"), located in the cytoplasm.Plasmids (small additional DNA rings)
    Amount of noncoding DNA 70-98% (lower gene density) 5-25% (higher gene density)
    Mitochondria Present Absent
    Ribosomes 80S 70S
    Cell Membrane Lipid bilayer Present
    Cell Wall Only in plants, fungi, and algae Present in most bacteria; exceptions include Mycoplasma which lack a cell wall
    Compartmentalization Membranes separate cellular compartments within the cytosol No compartmentalization
    Locomotive Structures (flagellum) Consist of bundles of microtubules and the motor protein dynein, surrounded by a plasma membrane Consist of repeating subunits of the protein flagellin (filament), a hook, and a motor complex that is anchored in the cell membrane

    Membrane Proteins

    • Proteins embedded in the lipid bilayer of membranes
    • Usually glycoproteins
    • Membrane protein content in the lipid bilayer: 20-80%

    Integral Membrane Proteins

    • Strongly bind to the lipid bilayer
    • Partially penetrate into the membrane
    • Transmembrane proteins: completely penetrate the lipid double layer (e.g., Na+/K+-ATPase)

    Peripheral Membrane Proteins

    • Poor binding to the lipid bilayer
    • Usually bind via electrostatic affinity or hydrogen bonds between a peripheral and an integral membrane protein

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    Description

    This quiz explores the fundamental differences between prokaryotic and eukaryotic cells, focusing on their structures and functions. Understand key concepts such as the lipid bilayer, transport mechanisms, and organelles involved in cellular processes.

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