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Exploring Cell Structure and Function

Apr 23, 2025

Structure and Function of the Cell

Introduction

  • Overview of cell structures and functions.
  • Encouragement to support channel by liking, commenting, and subscribing.

Nucleus

  • Nucleus as the Brain of the Cell:

    • Central organelle where cellular processes begin.
  • Nuclear Envelope:

    • Double-layered structure with an outer and inner layer.
    • Outer Layer: Contains ribosomes; site where mRNA exits to bind ribosomes.
    • Inner Layer: Contains lamins; important for nuclear envelope structure and cell division.
      • Disorders like progeria linked to lamins mutations.
  • Nuclear Pores:

    • Allow movement of ions, proteins, and nucleotides between cytoplasm and nucleus.
  • Nucleolus:

    • Site of rRNA synthesis and ribosome production.
  • Chromatin:

    • Composed of DNA and histone proteins.
    • Euchromatin: Loose form, involved in DNA expression and transcription.
    • Heterochromatin: Tight form, located near the nuclear envelope.
  • Functions of the Nucleus:

    • DNA Replication: Making more DNA.
    • Transcription: Converting DNA to RNA.
    • Types of RNA: tRNA, mRNA, rRNA.

Endoplasmic Reticulum

  • Rough ER:

    • Contains ribosomes; site of protein synthesis, folding, and glycosylation.
    • Synthesizes proteins for lysosomes, membranes, or excretion.
    • Packages proteins into vesicles for Golgi apparatus.
  • Smooth ER:

    • Site of lipid synthesis (fatty acids, phospholipids, cholesterol).
    • Detoxification via enzymes like CYP450.
    • Glucose-6-phosphate metabolism.
    • Calcium storage.

Golgi Apparatus

  • Structure:

    • Cis Golgi: Receives vesicles from ER.
    • Trans Golgi: Exports processed vesicles.
  • Functions:

    • Modifies proteins and lipids via glycosylation and phosphorylation.
    • Packages molecules for lysosomes, membranes, or excretion.

Cell Membrane

  • Components:

    • Phospholipid Bilayer: Polar heads (hydrophilic) and non-polar tails (hydrophobic).
    • Cholesterol: Regulates membrane fluidity.
    • Proteins: Integral and peripheral proteins involved in transport and enzymatic functions.
  • Function:

    • Acts as a selective barrier for diffusion and transport.

Lysosomes

  • Functions:
    • Contains hydrolytic enzymes for breaking down macromolecules.
    • Autophagy of organelles.
    • Autolysis of damaged cells.

Peroxisomes

  • Functions:
    • Contains catalase and oxidase for breaking down hydrogen peroxide.
    • Involved in fatty acid oxidation and lipid synthesis.
    • Minor role in ethanol metabolism.

Mitochondria

  • Structure:

    • Outer membrane (smooth, permeable).
    • Inner membrane (less permeable, folded into cristae).
    • Mitochondrial matrix (site of DNA and metabolic activities).
  • Functions:

    • Site of ATP synthesis via oxidative phosphorylation.
    • Involved in Krebs cycle, heme synthesis, urea cycle, gluconeogenesis, and ketogenesis.
    • Contains mitochondrial DNA inherited maternally.

Ribosomes

  • Structure:

    • Composed of large (60S) and small (40S) subunits.
    • Made of rRNA and proteins.
  • Functions:

    • Site of protein synthesis (translation).
    • Membrane-bound ribosomes produce proteins for lysosomes, membranes, or export.
    • Free ribosomes synthesize cytosolic proteins.

Cytoskeleton

  • Components:
    • Microfilaments (Actin): Involved in muscle contraction, cytokinesis, diapedesis, and phagocytosis.
    • Intermediate Filaments: Provide cell structure, anchorage to extracellular matrix, and organelles.
    • Microtubules: Involved in intracellular transport, cell division, and formation of cilia and flagella.

Conclusion

  • Recap of the cell structure and functions discussed.
  • Encouragement to apply similar study methods.
  • Expressions of gratitude towards viewers.