Physiology LE 1: Cell Structure and Function
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Questions and Answers

What is a characteristic of eukaryotic cells?

  • They are smaller than prokaryotic cells.
  • Their nucleus and most organelles are membrane-bound. (correct)
  • Their organelles are not membrane-bound.
  • They have a cell wall.

    • What is the primary function of the nucleus?

  • Cell division
  • Energy production
  • Protein synthesis
  • Storing the cell's hereditary material (correct)

    • Which of the following cells do not have a nucleus?

  • Cells in the liver
  • Cells in the brain
  • Mature human red blood cells (correct)
  • Mature human white blood cells

    • What is the result of transcription in the nucleus?

    <p>DNA to RNA</p> Signup and view all the answers

    What is the benefit of compartmentalization in eukaryotic cells?

    <p>It allows different organelles to perform different functions</p> Signup and view all the answers

    What is the role of the nucleus in regulating protein formation?

    <p>It regulates the formation of proteins and enzymes</p> Signup and view all the answers

    What is the term for the maintenance of a stable environment within a cell?

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

    What is the importance of isotonicity in intravenous formulations?

    <p>It prevents cell lysis</p> Signup and view all the answers

    What is the role of lysosomes in the processing of materials for degradation?

    <p>To degrade foreign substances and cellular waste</p> Signup and view all the answers

    What is the process by which a cell engulfs a bacterium?

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

    What is the function of catalase in the lysosome?

    <p>To oxidize toxic substances</p> Signup and view all the answers

    What is the fate of the debris after degradation in the lysosome?

    <p>It is excreted into the extracellular environment</p> Signup and view all the answers

    What is the role of the Golgi apparatus in cellular degradation?

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

    What is the process by which cells bring in materials from the exterior?

    <p>Phagocytosis, pinocytosis, and receptor-mediated endocytosis</p> Signup and view all the answers

    What is the difference between macroautophagy and microautophagy?

    <p>Microautophagy is a type of autophagy that involves the degradation of small portions of the cell</p> Signup and view all the answers

    What is the function of early endosomes in the processing of materials for degradation?

    <p>To pre-process materials for degradation by the lysosomes</p> Signup and view all the answers

    What is the site of β oxidation of fatty acid molecules?

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

    What is the function of catalases in peroxisomes?

    <p>To detoxify harmful substances</p> Signup and view all the answers

    How are peroxisomes formed?

    <p>By breaking off from the smooth endoplasmic reticulum</p> Signup and view all the answers

    What is the function of proteasomes?

    <p>To degrade proteins</p> Signup and view all the answers

    What is the function of mitochondria?

    <p>To generate ATP</p> Signup and view all the answers

    What is the role of ubiquitin in proteasomes?

    <p>To serve as a degradation signal</p> Signup and view all the answers

    What is the difference between peroxisomes and lysosomes?

    <p>Peroxisomes have different contents</p> Signup and view all the answers

    What is the effect of inhibiting proteasomes?

    <p>Antitumor activity</p> Signup and view all the answers

    What is the main function of tight junctions?

    <p>To fasten cells together and promote strength and stability</p> Signup and view all the answers

    What type of cytoskeleton material is the smallest and most abundant in cells?

    <p>Thin filaments</p> Signup and view all the answers

    What is the diameter of thin filaments?

    <p>7nm</p> Signup and view all the answers

    What is the function of gap junctions?

    <p>To allow the passage of molecules between adjacent cells</p> Signup and view all the answers

    What type of junction is usually found on the apical surfaces of cells that line certain mucosa?

    <p>Tight junctions</p> Signup and view all the answers

    What is the function of zonula adherens?

    <p>To act as attachments of microfilaments or other cytoskeleton</p> Signup and view all the answers

    What type of junction attaches cells to the basal lamina?

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

    What is the function of desmosomes?

    <p>To attach intermediate filaments</p> Signup and view all the answers

    What is the name of the type of junction that allows the passage of some molecules through the paracellular route?

    <p>Tight junctions</p> Signup and view all the answers

    What is the function of microfilaments?

    <p>To form an elastic support for the cell membrane</p> Signup and view all the answers

    What is the function of Mitochondrial Ca2+ uniporter (MCU) and regulatory protein MICU?

    <p>To mediate the uptake of Ca2+ across the mitochondrial inner membrane</p> Signup and view all the answers

    What happens when cytosolic Ca2+ is elevated?

    <p>Ca2+ is released from mitochondrial stores</p> Signup and view all the answers

    What is the role of mitochondria in apoptosis?

    <p>To play a central role in programmed cell death</p> Signup and view all the answers

    What is the diameter of Microtubules?

    <p>25 nm</p> Signup and view all the answers

    What is the function of Intermediate Filaments?

    <p>To provide support and rigid physical structures</p> Signup and view all the answers

    What is the characteristic of Intermediate Filaments?

    <p>They are less dynamic than actin microfilaments or microtubules</p> Signup and view all the answers

    Why are they called Intermediate Filaments?

    <p>Because their average diameter is between that of narrower actin microfilaments and wider myosin filaments</p> Signup and view all the answers

    What is the function of actin and myosin filaments in muscle cells?

    <p>To organize into a special contractile machine</p> Signup and view all the answers

    Study Notes

    Cellular Organelles

    • Peroxisomes: • Detoxify alcohol into acetaldehyde • Contain oxidases that combine oxygen and H+ to form H2O2 (hydrogen peroxide) • Used up by catalases to oxidize harmful substances • Site of β oxidation of fatty acid molecules and catabolism of D-amino acids, polyamines, and bile acids

    • Mitochondria: • Powerhouses of the cell – generate Adenosine triphosphate (ATP) • Total number varies depending on the cell type • Able to self-replicate, regulated by mitochondrial DNA

    • Proteasomes: • Specific to protein degradation • Regulate proteins that control cell-cycle progression and apoptosis • Work with ubiquitin, which serves as a degradation signal for numerous target proteins • Inhibition of the proteasome via antitumor activity (bortezomib)

    Cell Structure and Function

    • Phagocytosis: • Important in phagocytosis – function of WBC • Bacterium is ingested → fuses with lysosome • Enzymes present in lysosomes degrade the bacterium • Debris will be excreted into the extracellular environment

    • Lysosomes: • Play a major role in processing materials for degradation inside the cell • Includes materials from the exterior brought in through phagocytosis, pinocytosis, and receptor-mediated endocytosis • Materials are pre-processed for degradation by the lysosomes • Eventually mature into the multivesicular body or late endosomes before fusing with the lysosome for enzymatic degradation of contents

    Cytoskeleton

    • Intermediate Filaments: • 8-12 nm in diameter • Provide support and rigid physical structures • Also participate in cell division, cell motility, and movement of organelles

    • Microtubules: • 25 nm in diameter • Provide support and rigid physical structures • Participate in cell division, cell motility, and movement of organelles

    Cell Cytoskeleton Materials

    • Thin Filaments (Actin Microfilaments): • Smallest; most abundant protein in cells (7nm) • Frequently in the ectoplasm, forming an elastic support for the cell membrane

    Intercellular Connections

    • Tight Junctions (Zonula Occludens): • Found on the apical surfaces of cells that line certain mucosa and act as barriers (epithelium) • Fasten cells together and endow tissues with strength and stability • Allow the passage of some molecules through the paracellular route (“leaks”)

    • Zonula Adherens: • Usually continuous from the zonula occludens, acting as attachments of microfilaments or other cytoskeleton • “Adherens” = adhere

    • Desmosomes: • Apposed thickenings of two adjacent cells where intermediate filaments are attached

    • Hemidesmosomes: • Found on the basal surface, attaching cells to the basal lamina • Intracellularly, attachment for intermediate filaments

    • Gap Junctions: • Cytoplasmic “tunnels” between adjacent cells where molecules can pass through • Can open and close (water, ions, ATP, and action potentials pass through when it’s open)

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